* Approximate

** In general, up to one-fourth of the sugar may be replaced by corn syrup or mild-flavored honey. A larger proportion of corn syrup may be used if a very bland, light-colored typed is selected.

To make the syrup, dissolve sugar in lukewarm water, mixing until the solution is clear. Chill syrup before using.

Use just enough cold syrup to cover the prepared fruit after it has been placed in the container (about 1/2 to 2/3 cup of syrup per pint). To keep fruit under the syrup, place a small piece of crumpled parchment paper or other water-resistant wrapping material on top, and press fruit down into the syrup before sealing the container.

This document was extracted from "So Easy to Preserve", 6th ed. 2014. Bulletin 989, Cooperative Extension Service, The University of Georgia, Athens. Revised by Elizabeth L. Andress. Ph.D. and Judy A. Harrison, Ph.D., Extension Foods Specialists.

*blanching times are for water blanching unless otherwise indicated.

Acidification: To ensure safe acidity levels in whole, crushed, or juiced tomatoes, add the specified amount of acid as indicated in the table below. You can add the acid directly to the jars before filling them with the product. If desired, add sugar to balance the acidic taste, but do not leave acid out. Note that using vinegar may cause undesirable flavor changes.

Utah State University Extension: A Guide to Food Storage for Emergencies

FoodSafety.gov: Food Safety in a Disaster or Emergency

NC State Extension: Foods to Keep and Discard After a Power Outage

NC State Extension: Infant Food Safety During a Power Outage

University of Georgia: Preserving Food: What to do if the Freezer Stops

Storing Home Canned Foods

Packaging and Storing Dry Foods

Texas A&M Agrilife Extension: Safe Home Food Storage

University of Wisconsin Extension: Storing Fruits and Vegetables from the Home Garden

The FoodKeeper app is a great pocket resource for information about food storage to maximize freshness: FoodKeeper

Virginia Cooperative Extension: Dry Curing Virginia-Style Ham

University of Georgia Extension: Country Cured Ham

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To get you started, here's a list of the main categories of how-to content on the site: 

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University of Missouri Extension: Home Curing Bacon for a Mild Flavor

University of Georgia Extension: Basics of Sausage Making

Resources:

University of Georgia Extension: Preserving Food: Drying Fruits and Vegetables

Colorado State University Extension: Drying Fruits

Colorado State University Extension: Drying Vegetables

The following treatment results in a better product texture but must be carefully managed to avoid possible spoilage. Place jars in a canner filled half way with warm (120º to 140º F) water. Then, add hot water to a level 1 inch above jars. Heat the water enough to maintain 180º to 185º F water temperature for 30 minutes. Check with a candy or jelly thermometer to be certain that the water temperature is at least 180ºF during the entire 30 minutes. Temperatures higher than 185ºF may cause unnecessary softening of pickles. Caution: Use only when recipe indicates.

This document was extracted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA (Revised 2009).

Quantity: An average of 14 pounds is needed per canner load of 7 quarts; an average of 9 pounds is needed per canner load of 9 pints. A bushel weighs 48 pounds and yields 16 to 24 quarts – an average of 2 pounds per quart.

Quality: Select firm cucumbers of the appropriate size: about 1-1/2 inches for gherkins and 4 inches for dills. Use odd-shaped and more mature cucumbers for relishes and bread-and-butter style pickles.

This document was adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 2015.

Reviewed February 2018.

The many varieties of pickled and fermented foods are classified by ingredients and method of preparation.

Regular dill pickles and sauerkraut are fermented and cured for about 3 weeks. Refrigerator dills are fermented for about 1 week. During curing, colors and flavors change and acidity increases. Fresh-pack or quick-process pickles are not fermented; some are brined several hours or overnight, then drained and covered with vinegar and seasonings. Fruit pickles usually are prepared by heating fruit in a seasoned syrup acidified with either lemon juice or vinegar. Relishes are made from chopped fruits and vegetables that are cooked with seasonings and vinegar.

Be sure to remove and discard a 1/16-inch slice from the blossom end of fresh cucumbers. Blossoms may contain an enzyme which causes excessive softening of pickles.

Caution: The level of acidity in a pickled product is as important to its safety as it is to taste and texture.

• Do not alter vinegar, food, or water proportions in a recipe or use a vinegar with unknown acidity.
• Use only recipes with tested proportions of ingredients.
• There must be a minimum, uniform level of acid throughout the mixed product to prevent the growth of botulinum bacteria.

Ingredients

Select fresh, firm fruits or vegetables free of spoilage. Measure or weigh amounts carefully, because the proportion of fresh food to other ingredients will affect flavor and, in many instances, safety.

Use canning or pickling salt. Noncaking material added to other salts may make the brine cloudy. Since flake salt varies in density, it is not recommended for making pickled and fermented foods. White granulated and brown sugars are most often used. Corn syrup and honey, unless called for in reliable recipes, may produce undesirable flavors. White distilled and cider vinegars of 5 percent acidity (50 grain) are recommended. White vinegar is usually preferred when light color is desirable, as is the case with fruits and cauliflower.

Pickles with reduced salt content

Recipes for pickles with reduced sodium content are provided in Guide 6 of the USDA Complete Guide to Home Canning.

In the making of fresh-pack pickles, cucumbers are acidified quickly with vinegar. Use only tested recipes formulated to produce the proper acidity. While these pickles may be prepared safely with reduced or no salt, their quality may be noticeably lower. Both texture and flavor may be slightly, but noticeably, different than expected. You may wish to make small quantities first to determine if you like them.

However, the salt used in making fermented sauerkraut and brined pickles not only provides characteristic flavor but also is vital to safety and texture. In fermented foods, salt favors the growth of desirable bacteria while inhibiting the growth of others. Caution: Do not attempt to make sauerkraut or fermented pickles by cutting back on the salt required.

Firming agents

Alum may be safely used to firm fermented pickles. However, it is unnecessary and is not included in the recipes in this publication. Alum does not improve the firmness of quick-process pickles. The calcium in lime definitely improves pickle firmness. Food-grade lime may be used as a lime-water solution for soaking fresh cucumbers 12 to 24 hours before pickling them. Excess lime absorbed by the cucumbers must be removed to make safe pickles. To remove excess lime, drain the lime-water solution, rinse, and then resoak the cucumbers in fresh water for 1 hour. Repeat the rinsing and soaking steps two more times. To further improve pickle firmness, you may process cucumber pickles for 30 minutes in water at 180°F. This process also prevents spoilage, but the water temperature should not fall below 180°F. Use a candy or jelly thermometer to check the water temperature.

Preventing spoilage

Pickle products are subject to spoilage from microorganisms, particularly yeasts and molds, as well as enzymes that may affect flavor, color, and texture. Processing the pickles in a boiling-water canner will prevent both of these problems. Standard canning jars and self-sealing lids are recommended. Processing times and procedures will vary according to food acidity and the size of food pieces.

This document was adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 2015.

Reviewed February 2018.

There are no home canning directions for pickled eggs.  All of the following pickled egg recipes are for storage in the refrigerator.  Pickled eggs should never be at room temperature except for serving time, when they should be limited to no more than 2 hours in the temperature danger zone of 40 to 140 degrees F.

Caution:  Home pickled eggs stored at room temperature have caused botulism.  For the report from the Centers for Disease Control and Prevention (CDC), see http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4934a2.htm The Editorial Note in this report cautions against room temperature pickling and storage, also.  The CDC further cautions that to reduce the risk for botulism when pickling, food items should be washed and cooked adequately, and utensils, containers, and other surfaces in contact with food, including cutting boards and hands, should be cleaned thoroughly with soap and warm water. Containers (e.g., jars and lids) in which pickling will occur should be sterilized (e.g., placed in boiling water for a prescribed period). 

PICKLING TIPS

Pickled eggs are peeled, hard-cooked eggs in a solution consisting basically of vinegar, salt, spices, and perhaps other seasonings.  Pickling solutions are heated to boiling, simmered for 5 minutes, and poured over the peeled eggs.  Egg whites tend to be more tender if a boiling solution is used instead of room temperature solutions. 

Eggs used for pickling should have clean, sound shells.  Small or medium eggs are usually a good choice for pickling so the seasoning can penetrate into the egg.  Fresh eggs are the best to use for pickling to ensure the highest quality possible since the eggs will be stored over a relatively long period of time. However, eggs at least a few days old will peel better after boiling.

Cooking and Peeling Eggs

According to the Georgia Egg Commission, the following method of hard-cooking facilitates peeling of ultra fresh eggs.  Make a pinhole in the large end of the egg, place the eggs in a single layer in a saucepan, and cover with cold water to an inch above the layer of eggs.  Place a lid on the pan and bring eggs to a boil.  Remove the pan of eggs from the burner, leaving the cover in place, and allow to sit for 15-18 minutes, adjusting time up or down 3 minutes for larger or smaller eggs.  Immediately remove eggs from the pan of hot water with a slotted spoon to a bowl of ice water for one minute.  In the meantime, bring hot water to simmering.  After one minute in ice water remove eggs back to the simmering water for ten seconds.  The ten second interval is important because this allows the shell to expand without expanding the rest of the egg.  Peel immediately by cracking the shells of the egg all over.  Roll each egg gently between hands to loosen the shell.  Peel, starting at the large end of the egg.  The peeling may take place under cold running water to help wash the shell off the egg and to minimize the shell breaking into the white.

Another cooking method when you are less concerned about peeling of ultra-fresh eggs is to make a pinhole in the large end of the egg, place the eggs in a single layer in a saucepan, and cover with cold water to an inch above the layer of eggs.  Place a lid on the pan and bring eggs to a boil.  Turn down the heat and simmer for 15 minutes.  Place the eggs in cold water and when cool, remove shells.  Crack the shell of the egg all over.  Peel, starting at the large end of the egg.  The peeling may take place under cold running water to help wash the shell off the egg.

Containers for the Eggs

The container used for the eggs should be one that can be closed or sealed tightly; glass canning jars work well.  The eggs are to be completely covered with the pickling solution during storage.  A quart-size canning jar will hold about one dozen medium sized eggs.  For sterilizing glass jars, see Sterilization of Empty Jars.

Storing Eggs

After making the eggs, the eggs require some time to season (i.e., pick up the flavors from the pickling brine). Keep them refrigerated at all times. If small eggs are used, 1 to 2 weeks are usually allowed for seasoning to occur.  Medium or large eggs may require 2 to 4 weeks to become well seasoned.  Use the eggs within 3 to 4 months for best quality.

RECIPES

Each of these recipes uses 12 peeled, hard-cooked eggs.  The directions for each recipe are to bring all the ingredients except the eggs to a boil, reduce the heat and simmer for 5 minutes.  Pack no more than one dozen peeled, hard-cooked eggs loosely into a warm, pre-sterilized quart jar (or other similar size container which can be closed tightly).  There needs to be plenty of pickling solution, and enough to completely cover the eggs.  Pour the hot pickling solution over the eggs in the jar, cover, and refrigerate immediately.

RED BEET EGGS
1 cup red beet juice (from canned beets)
1½ cups cider vinegar
1 teaspoon brown sugar
a few canned whole tiny red beets (or several slices of beets can be used)

SWEET AND SOUR EGGS
1½ cups pasteurized apple cider
½ cup cider vinegar
1 package (about 12 oz.) red cinnamon candy
1 tablespoon mixed pickling spice
2 tablespoons salt
1 teaspoon garlic salt

DARK AND SPICY EGGS
1½ cups cider vinegar
½ cup water
1 tablespoon dark brown sugar
2 teaspoons granulated sugar
1 teaspoon mixed pickling spice
¼ teaspoon liquid smoke or hickory smoke salt
2 teaspoons salt

CIDERED EGGS
1½ cups pasteurized sweet apple cider or apple juice
½ cup white vinegar
6 thin slices of onion
1½ teaspoons salt
1 teaspoon whole pickling spice
1 peeled garlic clove

DILLED EGGS
1½ cups white vinegar
1 cup water
¾ teaspoon dill weed
¼ teaspoon white pepper
3 teaspoons salt
¼ teaspoon mustard seed
½ teaspoon onion juice or minced onion
½ teaspoon minced garlic or 1 peeled garlic clove

PINEAPPLE PICKLED EGGS
1 can (12 oz.) unsweetened pineapple juice*
1½ cups white vinegar
2 medium onions, peeled and sliced
¼ cup sugar
1 teaspoon salt
1 teaspoon whole pickling spice
*If sweetened pineapple juice is used, omit sugar

Acknowledgements

Recipes adapted and used with permission from:
Peter Piper Picked A Peck of Pickled Eggs, Georgia Egg Commission (undated).

Original Acknowledgements on the Georgia Egg Commission publication:  Dr. James C. Acton, Department of Food Science, Clemson University; Dr. Walter M. Britton, Department of Poultry Science, University of Georgia; The American Egg Board, Park Ridge, Illinois; and
Preserving and Pickling Eggs at Home, Cooperative Extension Service, University of Wisconsin.

Reviewed April 2014
Elizabeth L. Andress, Ph.D.
University of Georgia and National Center for Home Food Preservation.

• New Mexico State University Cooperative Extension Service: Home Canned Sweet Spreads Made with Green Chile
• North Dakota State University Extension: From the Garden or Orchard to the Table: Jams and Jellies from North Dakota Fruits
• Information on fruit butters, syrups, and pureés can be found under Canning Fruits and Fruit Products

• Home Canned Sweet Spreads Made with Green Chile, New Mexico State University Cooperative Extension Service
• Information on fruit butters, syrups, and pureés can be found under Canning Fruits and Fruit Products

The many varieties of pickled and fermented foods are classified by ingredients and method of preparation.

Regular dill pickles and sauerkraut are fermented and cured for about 3 weeks. Refrigerator dills are fermented for about 1 week. During curing, colors and flavors change and acidity increases. Fresh-pack or quick-process pickles are not fermented; some are brined several hours or overnight, then drained and covered with vinegar and seasonings. Fruit pickles usually are prepared by heating fruit in a seasoned syrup acidified with either lemon juice or vinegar. Relishes are made from chopped fruits and vegetables that are cooked with seasonings and vinegar.

Be sure to remove and discard a 1/16-inch slice from the blossom end of fresh cucumbers. Blossoms may contain an enzyme which causes excessive softening of pickles.

Caution: The level of acidity in a pickled product is as important to its safety as it is to taste and texture.

• Do not alter vinegar, food, or water proportions in a recipe or use a vinegar with unknown acidity.
• Use only recipes with tested proportions of ingredients.
• There must be a minimum, uniform level of acid throughout the mixed product to prevent the growth of botulinum bacteria.

Ingredients

Select fresh, firm fruits or vegetables free of spoilage. Measure or weigh amounts carefully, because the proportion of fresh food to other ingredients will affect flavor and, in many instances, safety.

Use canning or pickling salt. Noncaking material added to other salts may make the brine cloudy. Since flake salt varies in density, it is not recommended for making pickled and fermented foods. White granulated and brown sugars are most often used. Corn syrup and honey, unless called for in reliable recipes, may produce undesirable flavors. White distilled and cider vinegars of 5 percent acidity (50 grain) are recommended. White vinegar is usually preferred when light color is desirable, as is the case with fruits and cauliflower.

Pickles with reduced salt content

Recipes for pickles with reduced sodium content are provided in Guide 6 of the USDA Complete Guide to Home Canning.

In the making of fresh-pack pickles, cucumbers are acidified quickly with vinegar. Use only tested recipes formulated to produce the proper acidity. While these pickles may be prepared safely with reduced or no salt, their quality may be noticeably lower. Both texture and flavor may be slightly, but noticeably, different than expected. You may wish to make small quantities first to determine if you like them.

However, the salt used in making fermented sauerkraut and brined pickles not only provides characteristic flavor but also is vital to safety and texture. In fermented foods, salt favors the growth of desirable bacteria while inhibiting the growth of others. Caution: Do not attempt to make sauerkraut or fermented pickles by cutting back on the salt required.

Firming agents

Alum may be safely used to firm fermented pickles. However, it is unnecessary and is not included in the recipes in this publication. Alum does not improve the firmness of quick-process pickles. The calcium in lime definitely improves pickle firmness. Food-grade lime may be used as a lime-water solution for soaking fresh cucumbers 12 to 24 hours before pickling them. Excess lime absorbed by the cucumbers must be removed to make safe pickles. To remove excess lime, drain the lime-water solution, rinse, and then resoak the cucumbers in fresh water for 1 hour. Repeat the rinsing and soaking steps two more times. To further improve pickle firmness, you may process cucumber pickles for 30 minutes in water at 180°F. This process also prevents spoilage, but the water temperature should not fall below 180°F. Use a candy or jelly thermometer to check the water temperature.

Preventing spoilage

Pickle products are subject to spoilage from microorganisms, particularly yeasts and molds, as well as enzymes that may affect flavor, color, and texture. Processing the pickles in a boiling-water canner will prevent both of these problems. Standard canning jars and self-sealing lids are recommended. Processing times and procedures will vary according to food acidity and the size of food pieces.

This document was adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 2015.

Reviewed February 2018.

An Updated Look at Home Canning

Holly H. Garner, Elizabeth L. Andress, Ph.D., Anne L. Sweaney, Ph.D., The University of Georgia, Extension Foods and Nutrition, 208 Hoke Smith Annex, Athens, GA 30602-4356.

Presented at the Society for Nutrition Education Annual Conference, St. Paul, MN, July 29, 2002.

Abstract

Home canning is a traditionally popular means of preserving seasonal produce or specialty foods. The last comprehensive survey of U.S. canning practices, published in 1979 by USDA, studied consumer practices used in 1975. Significant lapses in appropriate techniques were documented and later survey reports by others have not revealed major shifts toward improved practices. As research yields new information about how to safely preserve foods and recommended practices for consumers are subsequently changed, people do not necessarily adopt the revised recommendations. Therefore, trained interviewers at the Survey Research Center, University of Georgia, conducted two surveys to determine practices and information sources currently being used by home canners. Between October 2000 and January 2001, 135 telephone interviews from households randomly selected throughout the U.S. were completed. In October 2001, 179 Georgians answered questions in another random telephone survey. Compared to the 1970’s, current findings indicate changes in the amount and types of foods canned at home, as well as methods used. They also document continued use of high-risk practices, including some that could lead to botulism. Friends or relatives are the primary source of instructions for today’s home canners (43.5% in the national survey, 55.1% in the Georgia survey); this practice could promote continued use of outdated information. More people can low-acid vegetables than tomato products or fruits and many use unsafe methods in doing so. Findings document knowledge and canning methods that should be targeted in educational programs for this population. This project was supported by CSREES-USDA under Agreement No. 00-51110-9762.

Introduction

Home canning is a popular means for preserving seasonal produce or specialty foods that helps maintain food for longer periods of time without losing its nutrient content. Although times have changed, many people still use the same food preservation methods that their grandparents did. This presents a problem because as more is understood about how to safely preserve foods the methods people use should be revised and updated as needed. Past surveys have shown that home canners use outdated and even unsafe procedures (2,3). Food was being preserved by methods that increase the risk for spoilage and the health problems that are associated with the consumption of these foods. Therefore, information is needed about the extent to which today’s consumers are canning foods at home, how they obtain their instructions, and if they are using safe procedures.

Objectives

The objectives for this study were to:

• Compare demographic characteristics of home canners today with those canning in the 1970’s.
• Compare the kinds of foods being canned at home today with those being canned in the 1970’s.
• Examine the sources that contemporary home canners look to for canning instructions and how they compare to what was used in the 1970’s.
• Determine if today’s home canners are using more appropriate processing methods than were used in the 1970’s.

Methods

Two telephone surveys were conducted in 2000-2001 by the National Center for Home Food Preservation (NCHFP) at the University of Georgia (UGA) in conjunction with the Survey Research Center (SRC), UGA. Structuring and supervision in an interviewer’s work is essential in order to gather data in a controlled and standardized fashion (4). Thus, interviewers trained in survey research and telephone-interviewing technology by the SRC were used for the interviewing in both surveys. Appropriate supervision during interviews provided quality control. Probability analyses estimated that the number of interviews conducted were more than sufficient to achieve the target levels of precision and accuracy in drawing conclusions on population responses based on sample estimates (1).

Between October 2000 and January 2001, 135 telephone interviews from households randomly selected throughout the U.S. were completed as part of a national survey. A 42-item survey instrument that included 16 open-ended questions was developed by the NCHFP and refined with the assistance of the SRC. 1244 eligible respondents were contacted; these yielded the 501 complete interviews of people canning and/or freezing food at home, for a cooperation rate of 40.3%. Of the 501 in the study, 135 (27%) canned food at home during 1999.

Then in November 2001, 179 Georgians answered a series of 10 home canning questions in another state telephone survey, the Georgia Poll. The Georgia Poll is conducted routinely in a random sampling of adult residents for the purpose of learning the attitudes and opinions of respondents towards several key sets of questions, as well as information about local and national affairs. The home canning interviews were a subset of 427 completed telephone interviews in the Georgia Poll. The cooperation rate for the overall study was 40.5%.

Data from these two UGA surveys were compared to the results of a 1976 national survey conducted by USDA (2). The methodologies for each of these studies are summarized in Table 1.

Results and Discussion

• Approximately 50-58.5% of home canners were 35-64 years of age in each survey. 28-33% were 35-49, while another 20-25.5% were 50-64 years old.
   
• In the USDA national sample, 39% were 50 years and older and 31% were under age 35. In the NCHFP national sample, there was a higher percentage (41.2) aged 50 years and older and a smaller percentage (24.4) under age 35. The GaPOLL sample had more canners in the younger age categories (under age 65) than the NCHFP sample.
   
• The numbers of home canners with at least a high school education were higher in the NCHFP (81.5%) and GaPOLL (93.1%) than in the 1975 USDA study (63%). In addition, the number of home canners with formal education beyond high school was also much higher in the more recent surveys (53.3% NCHFP and 67.3% GaPOLL versus 27% USDA).
   
• The high levels of missing information on income in the NCHFP (40.7%) and GaPOLL (29.1%) surveys make it difficult to describe the true income distribution of those participating in home canning. Of those choosing to report their income, 16.3% and 19.3% (NCHFP and GaPOLL respectively) have household incomes of less than $35,000/year; 43% and 51.6% (NCHFP and GaPOLL respectively) have incomes of more than $35,000.
   

• In 1975, tomatoes were being canned by 73% of the households surveyed. Today the percentage canning tomatoes has decreased (60% and 34.3% NCHFP and GaPOLL respectively) and vegetables (71.1% and 47.8% NCHFP and GaPOLL respectively) are now the most frequently canned product.
• The increase in the percentage of households canning vegetables focuses concern on the use of improper methods for canning vegetables, which require a pressure processing method.
• The percentage of households canning fruits has decreased slightly from 1975.

• As in 1975, the most often cited source of instructions in the NCHFP and GaPOLL surveys is friends or relatives (43.5% and 55.1% respectively).
• The percentage of home canners using the recommended USDA and Extension Service Publications in 1975 was very small but today that percentage has decreased even more.
• In 1975, 42.6% of home canners were using cookbooks as their source of instruction, but today that number has decreased (16.8% and 15.8% NCHFP and GaPOLL respectively).

• The usual USDA recommended processing method for canning fruits and tomatoes is boiling water canning, so one would expect a majority of home canners to be using this method. Recommended pressure processes are available as alternatives to the boiling water canner. Oven and open kettle canning have not been recommended by USDA as methods for fruits and tomatoes since 1943. Table 5 contains the methods that home canners report using for the acid-food categories of fruits and tomatoes.
   
  • The percentage of home canners using boiling water canning for fruits and tomatoes has not increased much since 1975. However, the percentage using the open kettle method (no processing of the filled jar) has decreased from 43.6/35.1 (fruits/tomatoes) to 14-22 (NCHFP-GaPOLL).
     
  • More people are using a pressure cooker for processing fruits and tomatoes now than in 1975. A smaller percentage of the NCHFP respondents reported using a pressure canner than in either USDA’s 1975 survey or the GaPOLL.
     
  • The NCHFP and GaPOLL surveys both indicated similar percentages using the boiling water canner for processing fruits and tomatoes. The percentages using all other methods were not consistent in these two surveys.
     
• Recommended USDA processing procedures for home canning of vegetables other than tomatoes have only included pressure processes since 1943. Furthermore, boiling water, oven and open kettle canning have been described as unsafe for low-acid foods since that time. Beginning in 1957, USDA Home and Garden Bulletins included a statement to add 20 minutes to processing times used for pressure canners when using a pressure cooker. Therefore, in 1975, USDA did recommend a method for processing vegetables in a pressure cooker (saucepan). However, this endorsement was removed from their recommendations in 1988 with the publishing of the Complete Guide to Home Canning. This latter bulletin stated that recommended small pressure canners hold four quart-size jars; pressure saucepans with smaller volume capacities are not recommended for use in canning. The methods home canners report using for low-acid vegetables are shown in Table 5.
   
  • In 1975, slightly more than half of home canners were using either a pressure canner or cooker for vegetables (56.6 combined), as recommended. A smaller percentage (43.1 combined) reported using either of these methods for vegetable mixtures. Less than half of home canners in the NCHFP (44.2 %) and GaPOLL (32.8 %) surveys reported using either pressure-based method.
     
  • The number of home canners using no processing (the open kettle method) for vegetables was high enough to cause concern in 1975. Unfortunately, today there appears to be little decrease in the percentage of home canners who choose to follow this very risky practice.
     
  • The percentages of home canners today (3.3 and 7.4, NCHFP and GaPOLL respectively) also reporting the use of oven canning methods are of concern.
     

• Prior to 1978, paraffin was recommended in USDA publications for sealing jellies and jams. Then in a 1978 USDA bulletin, a 5-minute boiling water process was recommended for sealed jars of jellies, jams, conserves, marmalades, and preserves for those residing in warm or humid climates; the use of paraffin was restricted as an option for jelly only. USDA has recommended only a boiling water process for all jams and jellies since 1988.
   
• The GaPOLL results indicate that the number of home canners using a boiling water process for jellies and jams has increased since 1975. However, less than half of home canners today (48.8 percent) are following this practice, while 35% report using open kettle methods, 9% oven canning and 7% pressure canning. In 1975, 85/87% (for jams/jellies) used the open kettle method, while 12.6/9.5 and 3.9/5.1 used boiling water and pressure methods, respectively.
   

Conclusions

• Current surveys reveal that greater adoption of science-based home canning techniques is needed, a finding similar to the 1975 national USDA survey.
   
• One finding of greatest concern is the lack of pressure-based processing methods for vegetables. A large percentage of home canners are at high risk for foodborne illness, including botulism.
   
• Findings document risky practices and knowledge that should be targeted in educational programs and publications.
   
• Ongoing analyses indicate interactive effects for age and education with choices of processing methods and sources of instruction.
   

References

1. Bason, J. 2001. Materials and methods statement. Survey Research Center, The University of Georgia, Athens, GA.
    
2. Davis, C. A., and L. Page. 1979. Practices used for home canning of fruits and vegetables. USDA Home Economics Research Report No. 43. Washington, DC: Government Printing Office.
    
3. Hatfield, K. 1981. Changing home food production and preservation patterns. National Food Review 27:22-25.
    
4. Lavrakas, P. J. 1987. Telephone Survey Methods: Sampling, Selection and Supervision. Applied Social Research Methods Series, Volume 7. SAGE Publications, CA.
    

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Garner, H.H., E.L. Andress, and A.L. Sweaney. 2002. An updated look at home canning. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied.  This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.  An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Disseminating Science-based Home Food Preservation
Information on the Internet

B. A. NUMMER1, E. L. Andress1, J. A. Harrison1, M. A. Harrison2, and W. L. Kerr2. (1) Dept. Foods and Nutrition Extension, University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602, (2) Dept. Food Science and Technology, University of Georgia.

Paper 46B-5. Presented at the Institute of Food Technologists Annual Meeting Anaheim, CA, June 17, 2002.

Abstract

Home food preservation remains an important and popular cultural activity. The safety of these products and processes remains the number one concern.  The National Center for Home Food Preservation (NCHFP) was created to help meet the needs of both Extension agents and consumers for science-based information. As part of the NCHFP mission a web site was created to locate, review, and disseminate research-based home food preservation information.  The web site, www.homefoodpreservation.com, offers publications from U.S.D.A. guides and bulletins, the University of Georgia, literature reviews of current topics, links to other state Cooperative Extension homepages, seasonal tips, multimedia demonstrations, FAQs, contact lists and a variety of other resources.  Initial feedback from a sampling of Cooperative Extension agents has been favorable. Experienced home preservers have also given favorable reviews, while inexperienced home food preservers commented that they are a bit overwhelmed.  The initial comments and popularity of the site indicates that it is meeting its objectives of providing resources to Cooperative Extension professionals and increasing public awareness of science-based safe home food preservation techniques.

Introduction

According to the latest Nielsen Media Research survey there are now 92 million Americans over the age of sixteen on the Internet (CommerceNet, 1999). This is almost half of the population. This incredible growth in access has made the Internet an excellent source for educational and reference materials.  The Internet is fast becoming an important tool for food safety specialists, allowing for rapid location of specific information.  One food safety resource, the National Food Safety Database, had over 10,000 requests per day, over 145,000 distinct users, and an international audience of 85 countries (Tamplin, 1998). The need for access to food safety information will no doubt markedly increase in the coming years, with new food safety regulations, media attention, and advances in Internet technologies.

Material and Methods

Web site.  The web site was constructed by the Web Instructional Development group, a part of the University of Georgia Center for Continuing Education, Athens, GA and members of the National Center for Home Food Preservation management team.  

Design Analysis.  Site design analysis was performed using criteria developed by authors at Yale and Dartmouth Universities (Lynch and Horton, 1997).

Assessment.  An assessment of objectives was obtained from a small survey group of 37 educators and consumers and from direct feedback.  Web site users were encouraged to send direct feedback and a 15-question survey was created (Exhibit 1) to solicit users feedback. 

Results and Discussion

User-centered design.  The NCHFP web site users are both consumers and professionals.  Consumers range from first-time home food preservers to highly experienced food preservers.  Professionals include Cooperative Extension professionals, teachers, researchers, journalists, and publishers.  The survey group consisted of 17 Cooperative Extension agents, 17 consumers, and 3 others. 

The front page.  As an informational site, the front page (Figure 1) establishes an overall visual design with the NCHFP logo.  It identifies and gives a brief explanation of the purpose of the site, and provides a site overview by presenting links to its major sections. This page answers the questions, Where am I? What is it like here? What do these people do? What kind of stuff will I find?  As a reference site visitors are able to tell at a glance if the information they are seeking is inside.  Ninety-two percent felt the home page was “very useful” in its current form.

Figure 1. National Center for Home Food Preservation Front Page

Objectives.  Clear and simple goals are key to successful web sites (Table 1).

Authors.  It is critical the audience understand who the NCHFP is and the USDA message of using only “science-based” information.  The survey group was asked “On your first visit to the web site was it clear whom the NCHFP was?”  Eighty-one percent said “yes”, 16% said “yes, but I had to look some” and 3% said “no, I found that information, but it was not completely clear”.  A second question asked, “On your first visit to the web site was it clear what “science-based” guidelines and recommendations on Home Food Preservation are?”   Sixty-eight percent responded “yes”, 22% responded “yes, but I had to look some”, 5% responded, “no, I found that information, but it was not completely clear, and 5% responded they “did not find that information”. 

Navigation.  An easy hierarchal structure amenable to both the experienced web surfer and the novice was desired.  Eighty-six percent of our survey group responded that the web site was “well categorized and easy to follow”; while 14% responded that it “could be figured out with some effort”.

Pages.  Individual pages were created to be simple and consistent.  The survey group responded that the placement of buttons and links, colors used, and overall page layouts were “well done and appealing” (76%), “pretty good” (19%), and “nothing special” (3%).   The survey group also responded that the graphic appeal of our site was “professionally done and contemporary in appeal” (73%), “pretty good” (24%), and “nothing special” (3%). 

Bandwidth.   Sixty-five percent of the respondents had a telephone modem or similar slow Internet connection (including all consumer respondents), while 38% reported having a cable modem or similar faster Internet connection.   Keeping bandwidth usage to a minimum was critical in serving these users.  Some of the Adobe Acrobat™ PDF and Real Media™ files are large for slower connections (Table 2). Some respondents indicated the site was too slow (1 reply) or they had difficulty with large multimedia files (6 replies).  Providing alternate sources (e.g. CD-rom, print, downloadable files) for heavy bandwidth files would help alleviate some of these problems.

Interactivity and Search. As both an informational and reference web site we sought to provide quick access to relevant information.  When information cannot be located in a menu the search section can guide a user through internal and external search resources to find information.  There is also an “Info request” form.  Over 85% of the survey group indicated they found the search features “very useful”.  Written feedback from novice computer users indicated they had difficulties understanding and using these search functions.   Thus, redesigning the “search” topic to make it a logical and simplistic tool more amenable to both novice and expert computer users will be considered.

Multimedia.  Some topics benefit by visual enhancement.  We created digital video, audio, and animation.  This section was the most troublesome of the web site content where 51% of our survey group felt the multimedia section was less than “very useful”.  Survey group participants had problems with slow connections, downloading required software, and in getting the multimedia software to run.  To address these problems additional means of delivering these files are being considered (e.g. CD-rom).  The results may have also been influenced by the minimal content of this section.  More content is scheduled to be added. 

Change in knowledge and behaviors.  Initial comments and popularity of the site indicate that it is meeting its objectives of providing resources to the Cooperative Extension System and increasing public awareness of science-based safe home food preservation techniques.  Overall 34 of 37 surveyed felt that the web site would be a positive influence to serve the home food preservation needs of educators. One felt there would be “no influence” due to the lack of usable materials and two consumers had “no opinion”.  All 37 respondents felt the web site would be a positive influence on consumers.   Seventy-one percent of the survey group felt the “more information on the web site the better”.  Two respondents, both were novice food preservers, felt the information “seemed like too much” or was “far too much”.   This may suggest the need for “beginner friendly” resources for an introduction to the web site and its contents.

Suggestions.  Written suggestions for materials to add included: a site map, why preserve foods for beginners, what your Extension office can do for you, what’s new page for the site, Latin foods, low sugar recipes, links to master gardeners, metric conversions, links for international visitors, a food pH guide, hazardous recipe listing, food safety of preserved gifts, new fruits and vegetable varieties, as well as numerous requests for narrow information topics (e.g. lemon curd, and pomegranate).  Additional materials are currently being created and reviewed for placement on the web site.  A full-time Webmaster has been hired for site management, further design and building of the site, improvement of access in areas identified by this research, and ongoing evaluation of the site.  

References

Lynch, P. and S. Horton, 1997. Web Style Guide. Yale University. Available at: http://info.med.yale.edu/caim/manual/ Accessed 17 May 2002.

Access Board.  2001. Web-based Intranet and Internet Information and Applications.  Washington DC. Available at: http://www.access-board.gov/sec508/guide/1194.22.htm. Accessed 1 Jun 2002.

CommerceNet. 1999. Industry Statistics.  Available at: http://www.commerce.net/research/stats/wwwpop.html. Accessed 5 Jun 2002.

Tamplin, M.L. 1998. National Food Safety Database.  Project No. 98-EFSQ-1-0330.  The Food Safety and Quality National Initiative Abstracts. Washington, DC.: U.S. Department of Agriculture.  Available at: http://www.reeusda.gov/pas/programs/foodsafety/98abs.htm. Accessed 10 Jun 2002. 

Exhibit 1.  Survey for Center Web Site

The National Center for Home Food Preservation

1. Describe yourself

45% [17] Cooperative Extension Agent
        [    ] State Cooperative Extension Specialist or Program Assistant
  3% [  1] Other University Faculty or Staff
        [    ] Extension Volunteer / Master Food Preserver
45% [17] Consumer (Home Food Preserver)
  5% [  2] Other ____________________ e.g. Food Writer, Author, etc.

Total 37

2. Rate your experience level in Home Food Preservation

43% [16] Experienced
24% [  9] Average Experience
24% [  9] Some Experience
  8% [  3] Little experience
        [    ] No experience

Total 37

3. What type of Internet connection are you using?

14% [  5] Below 33.6 Kbps telephone modem or I don’t know numbers,
                but it is a slow connection.
49% [18] 56Kbps telephone modem.
  3% [  1] Cable modem or I don’t know speeds, but it is a fast
                connection.
35% [13] University or other high speed network connection

Total 37

4.  On your first visit to the web site was it clear whom the National Center for Home Food Preservation was?

81% [30] Yes
16% [  6] Yes, but I had to look some
  3% [  1] No, I found that information, but it was not completely clear
        [    ] No, I had trouble finding that information

Total 37

5. On your first visit to the web site was it clear what “science-based” guidelines and recommendations on Home Food Preservation are?

68% [25] Yes
22% [  8] Yes, but I had to look some
  5% [  2] No, I found that information, but it was not completely clear
  5% [  2] No, I had trouble finding that information

Total 37

6. In your opinion, the amount of information on our web site is: 

  3% [  1] Far too much
  3% [  1] Seems like too much
23% [  8] Appropriate
71% [25] The more the better

Total 35 No reply 2

7. In your opinion, the organization of our web site is: 

86% [31] Categorized and easy to follow
14% [  5] Could be figured out with some effort
        [    ] Confusing and difficult to follow

Total 36 No reply 1

8. In your opinion, the graphic appeal of our home page is: 

73% [27] Professionally done and contemporary in appeal
24% [  9] Pretty good
  3% [  1] Nothing special

Total 37

9. In your opinion, the placement of buttons and links, colors used, and overall page layouts are: 

76% [28] Well-done and appealing
19% [  7] Pretty good
  3% [  1] Nothing special

Total 37

10.  Please visit and rate the section topics of our web site for usefulness (please do not rate the topics on content - more content will be added to sections as we continue our project).  Place a check mark in the box of your choice.  

11.  Please write section topic ideas that are not included in our web site that you feel would be useful (e.g. a site map).

Site Map, Why preserve foods for beginners, what your extension office can do for you, what’s new page for the site, latin foods, low sugar pages, links to master gardeners, metric conversions,

12.  If you found useful information, was it available in a computer format that was accessible to you?  (e.g. MS PowerPoint PPT, Adobe Acrobat PDF, Macromedia Flash, and Real Media).

81% [30] Yes
19% [  7] Yes, but I had to or would need to download software to
                make the information accessible.
        [    ] No

Total 37

13. In your opinion, will this web site serve educators in the area of home food preservation?

92% [34] Positive influence
  3% [  1] No influence (responded not enough materials yet for educ.)
        [    ] Negative influence
  6% [  2] No opinion

Total 37

14. In your opinion, will this web site serve consumers in the area of home food preservation?

100% [37] Positive influence
          [    ] No influence
          [    ] Negative influence

Total 37

15. What sources of frustration did you encounter on the web site?  Please elaborate.  You may also write general comments here.

Site was too slow (2 replies), trouble with Real Media/multimedia (6 replies), overwhelming information overload.

Reviewed by Elaine D’Sa, Ph.D. and Elizabeth Andress, Ph.D., National Center for Home Food Preservation.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:
Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Nummer, B.A., E. L. Andress, J. A. Harrison, M. A. Harrison, and W. L. Kerr.  2002. Disseminating science-based home food preservation information on the Internet.  Athens, GA: The University of Georgia, Cooperative Extension Service

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied.  This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.  An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Heat Penetration Studies of Stewed Tomatoes in 6, 8, and 17 Quart Household Pressure Retorts

R.J. Pakola and E.L. Andress, Dept. of Foods and Nutrition, The University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602-4356.

Paper 46B-7. Presented at the Institute of Food Technologists Annual Meeting Anaheim, CA, June 17, 2002.

Abstract

Most current home pressure canning recommendations were developed using standard 17 to 21 quart pressure retorts. Today's marketplace offers a variety of smaller pressure-based cookers/canners. Retort size has the potential to affect come up and cooling rates, which contribute to the sterilizing value of a pressure process. As heating and cooling times are reduced so is total lethality. The objective of this study was to compare f(h) values, cumulative lethalities, and potential safe process times during pressure processing of stewed tomatoes in 6, 8, and 17 quart household pressure retorts. Stewed tomatoes were prepared and packed into 8 oz glass home canning jars. Jars were processed at 121.1°C for 25 minutes in 6, 8, and 17 quart pressure retorts after a 10 minute exhaust of the retort. Heat penetration data were collected at the cold spot, previously determined to be the geometric center of the jar. Continuous temperature profiles from 15 replications were collected using copper-constantan needle thermocouples connected to an electronic data logger. Potential process times and cumulative lethal rates were calculated for the destruction of Clostridium botulinum spores. The cumulative lethal rate did not reach the target F0 (3.0) during the process. The majority of the lethality was achieved during cooling. Processing in smaller retorts resulted in lower f(h) values (p<.001). Calculated process times from the data collected so far were found to be equivalent but due to the need to verify some data with additional work, a final conclusion about process schedules cannot be made at this time, Home canning in very small retorts should be avoided until safe process recommendations can be determined.

Introduction

Currently, home canning in smaller pressure retorts is not recommended by USDA and the Cooperative Extension System (USDA, 1994). Existing recommendations were determined using standard size home canning pressure retorts that have a 17 or 21 quart capacity. Smaller pressure retorts are widely available in 4, 6, and 8 quart capacities. "Pressure canner" is a term usually associated with 16 quart and larger capacities. A recent survey by the National Center for Home Food Preservation indicates that people are using smaller pressure retorts to can food at home (Andress, 2001). Past research suggests that 4 quart retorts require a longer process time to achieve an equivalent lethality (Taube and Sater, 1948; Nordsiden and others, 1978). Thus home canning in smaller retorts may not produce a safe product.

Objective

The purpose of this study was to compare heating characteristics and potential process recommendations of a product in standard and smaller size pressure retorts.

Materials and Methods

Stewed tomatoes were selected for this study; the recipe used in this study is described in Figure 1. Half pint jars were filled with 200 + 10 grams stewed tomatoes for all experiments. Each retort load consisted of five jars. Jars were processed at 121.1°C for 25 minutes following a 10 minute exhaust (vent).

Heating profiles were collected in 6, 8, and 17 quart capacity aluminum pressure retorts using Ecklund needle type copper-constantan (type "T") thermocouples.

The cold spot, or slowest heating point in the jar, was determined from data taken at the center and half inch increments below the center by using 4 different lengths of needle probes. Data were recorded using the DAS-TC (Keithley Instruments, 1996) data acquisition system. The rate of heating, expressed as f(h), was determined and compared using the data analysis software (SAS Inc., 1999-2001).

For process calculations, heating profiles were collected at the cold spot in 15 jars of stewed tomatoes per retort size. Data were recorded using the E-Val™ Monitoring System (Ellab Inc., 2000). Data were imported into thermal processing software (TechniCAL Inc., 1998) to determine f(h) values, potential process times (Bb), and cumulative lethalities. A target lethality (F0) of 3.0 minutes was selected based on the choice of Clostridium botulinum as the microorganism of concern.

Figure 1. Stewed Tomatoes Recipe

Ingredients

• 2 quarts halved tomatoes
• ¼ cup chopped celery
• ¼ cup chopped onions
• 2 teaspoons celery salt
• 2 teaspoons sugar
• ¼ teaspoon salt

Procedure

Select firm, ripe Roma tomatoes. Wash and place tomatoes in boiling water until skins split. Dip in cold water and remove the skins and cores. Slice tomatoes into halves. Combine all ingredients in a large saucepan and cover. Heat to a boil and simmer for 10 minutes. Fill five half-pint canning jars, leaving ½ inch headspace. Remove air bubbles, adjust headspace if necessary, and wipe jar rims. Secure two-piece metal lids. Process jars in a pressure canner.

Results and Discussion

COLD SPOT LOCATION

The f(h) value it the slope of the straight line portion of the heating curve. A larger f(h) value indicates a slower rate of heating. The slowest heating point of stewed tomatoes in half pint jars is the geometric center of the jar (Table 1).

THERMAL CHARACTERISTICS

Jar temperature did not start to increase until the end of the 10-minute exhaust (Table 2). Mean jar temperatures achieved by the end of the 25-minute process were the same (p<.001) in the 6 and 8 quart retorts (Table 2).

EFFECT OF RETORT SIZE

Retort temperatures across experiments were controlled (Table 3).

The f(h) values increased with retort size (Table 3). The jars processed in the smaller retorts had a faster rate of heating (p<.01). The difference between the f(h) values was not significant between the 6 and 8 quart retorts, probably because there is less difference in size between the 6 and 8 quart retorts as compared to the 8 quart and 17 quart retorts.

Target F0 (3.0) was not achieved in any retort by the end of the process time; at least 2/3 of the cumulative lethality was achieved during cooling (Table 3).

Even though the average calculated process time appears to follow the trend of f(h) values, the maximum achieved in each size retort does not. In practice, home canning process times are rounded off to the next highest 5-minute interval. Therefore, if these results were to be used for recommending a process time, based on the worst-case jar in each retort, the recommended process time for all three sizes would be 40 minutes (Table 3).

Conclusions

The target F0 was not achieved during the process. Most of the cumulative lethality was acquired during cooling.

Jars processed in smaller retorts (6 and 8 quart) had smaller f(h) values indicating a faster rate of heating during the process time than occurred in the 17 quart retort. This resulted in higher cumulative lethality for the smaller retorts, which was unexpected. These results are not consistent with past research on smaller retorts.

The 6 quart retort did not provide reliable cooling data. Conclusions cannot yet be drawn about the entire process in all three sizes of retorts.

In addition, the 17 quart retort had shorter come-up and cool down times than have been previously documented with older models (Toepfer et al., 1946). The 17 quart retort will hold a much larger volume than the 6 and 8 quart retorts; this study limited the number and size of jars to what was determined to be a full load in the smallest retort. Future work should explore the effect of varying the number and size of jars in the 17 quart retort.

References

1. Andress, E. L. 2001. A national survey of current home canning practices in the US. National Center for Home Food Preservation, Department of Foods and Nutrition, The University of Georgia, Athens, GA. Unpublished data.
    
2. Ellab Inc., 2000. E-Val Basic, V. 2.0. Software and Documentation, Ellab Inc., Arvada, CO.
    
3. Keithley Instruments Inc., 1996. DAS-TC Data Acquisition System. Keithley Instruments Inc., Cleveland, OH.
    
4. Nordsiden KL, Thompson DR, Wolf ID, Zottola EA. 1978. Home canning of food: effect of a higher process temperature (250° F) on the safety of low-acid foods. J Food Sci. 43:1734-1737.
    
5. SAS Inc., 1999-2001. Statistical Analysis Software, v. 8.02. for Windows, SAS Institute Inc. Cary, NC.
    
6. Taube, K. and Sater, V.E. 1948. Canning vegetables in the pressure saucepan. J Home Econ. 40:197-198.
    
7. TechniCAL Inc., 1998. Carlsoft, V. 1.3.3. Thermal Processing Software, TechniCAL, Inc., New Orleans, LA.
    
8. Toepfer, E.W., Reynolds, H., Gilpin, G. L., and Taube, K. 1946. Home canning processes for low-acid foods. USDA Technical Bulletin No. 930. Washington, DC: Bureau of Home Economics, U.S. Department of Agriculture.
    
9. USDA. 1994. Complete guide to home canning. Agriculture Information Bulletin No.539. Washington, DC: CSREES-U.S. Department of Agriculture.
    

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Pakola, R.J. and E.L. Andress. 2002. Heat penetration studies of stewed tomatoes in 6, 8, and 17 quart household pressure retorts. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Effect of Fill Weight and Initial Temperature on
Processing Time for a Home Pickled Jicama Relish

H.H. Garner and E.L. Andress, Department of Foods and Nutrition, The University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602-4356.

Paper 46B-6. Presented at the Institute of Food Technologists Annual Meeting Anaheim, CA, June 17, 2002.

Abstract

Pickled vegetables are popular home preserved condiments. The increasing variety of produce in the marketplace offers opportunities for greater diversity in condiments such as salsa and relishes than has traditionally been available in the U.S. Jicama was studied for its potential use in home pickled products with a crisp texture. The objective of this study was to determine the effect of typical consumer procedural variations on heat penetration when processing an acidified jicama relish recipe. Variations were made in fill weight and initial temperature (IT) of the filled jars. An original recipe with an equilibrium pH of 3.5 was developed for heat penetration studies using a hot pack, pint jars and boiling water canner. Product temperatures were continuously recorded at the predetermined cold spot throughout come-up time, 35 minutes in boiling water, and air cooling of jars. Fifteen jars (five jars in each of three canner loads) were used for each procedural variation of fill weight and IT. Processing was done in a 17-quart boiling water canner on a household gas range. Fill weight had a significant impact on both maximum jar temperature obtained and final process time recommendation. Heat applied during come-up had no effect on jar temperature with the overfill. A decrease of 5°C (64.5 vs. 69.7) in IT had no effect on either maximum jar temperature reached at the end of come-up or the 35 minutes at boiling. However, analysis of the maximum jar temperature reached at the end of come-up or the 35 minutes at boiling. However, analysis of the worst case low IT jar would result in a longer process time than for the higher IT product. This study documents the effects of some consumer practices on process lethality for a cubed relish product. Overfills should be avoided to insure expected heating rates and final maximum temperatures. Specifying a minimum number of jars to a home canning recipe could be considered.

Introduction

• Pickled products are low acid foods that have had their pH lowered to 4.6 or below by the addition of acid or vinegar before thermal processing in order to produce a safe product.
   
• A USDA survey of home canning practices in the 1970's (Davis and Page, 1979) indicated that 20% of home canners make products with combinations of acid and low acid ingredients and use inappropriate methods for processing; a 2000-2001 survey by the University of Georgia had similar findings (Andress, 2001).
   
• Improperly formulated pickled products may allow for growth of the organism C. botulinum, which leads to toxin formation and the potentially fatal food intoxication, botulism.
   
• Improperly processed pickled products may allow room for the growth of mold, yeast and/or bacteria that produce spoilage.
   

Hypotheses

1. As fill weight of jars increases, the f(h) value and required processing time will increase.
2. As initial fill temperature of jars decreases, required processing time will increase.

Methods

A thermal process (home canning) recommendation was developed for pint jars of an original pickled vegetable relish (jicama, red and yellow bell peppers, onion, hot pepper, spices and vinegar/sugar brine), see Figure 1 (Garner and Andress, 2001). Determination of the cold spot for this product and jar combination was made using data collected for heat penetration curves at 5 potential cold spot locations in the jars in 12 canner loads, see Table 1.

Two levels of two procedural variations were used in testing for process calculations. Temperature profiles were compared for two fill weights (454g, 490g) and two fill temperatures (69.7°C, 64.5°C) of the relish. A total of 12 to15 data points (replications) at the determined cold spot were used for the process calculation. This was accomplished by using thermocouples in each of five jars in three different canner loads of each of the three fill methods (standard, low initial temperature, and overfill).

A total of 15 data points (replications) at the determined cold spot were used for the process calculation. This was accomplished by using thermocouples in each of five jars in three different canner loads of each of the three fill methods (standard, low initial temperature and overfill).

Processing was done in a boiling water canner using the stovetop burners of a household gas range (Magic Chef model 3267XTW). Data were recorded using an Ellab E-Val™ Monitoring System and software and Ecklund needle Type T copper-constantan thermocouples. Analysis of variance was used to determine if significant (p<0.01) differences existed between the treatments using the General Linear Model procedure in SAS 8.2 (2001).

Figure 1. Spicy Jicama Relish Recipe

9 c. diced jicama
1 Tbsp whole pickling spice
1 2-inch stick cinnamon
8 c. white 5% distilled vinegar
4 c. sugar
2 tsp. crushed red pepper flakes
4 c. diced yellow bell pepper
4-1/2 c. diced red bell pepper
4 c. chopped onion
2 fresh (about) 6” fingerhot peppers, finely chopped and partially seeded

1. Wash, peel and trim jicama; dice.
    
2. Place pickling spice and cinnamon on a double-layer of 100% cotton cheesecloth. Bring corners together and tie with a clean string.
    
3. In a 4-quart Dutch oven or kettle combine pickling spice bag, vinegar, sugar, and crushed red pepper. Bring to boil, stirring to dissolve sugar. Stir in diced jicama, sweet peppers, onion and fingerhots. Return mixture to boiling. Reduce heat and simmer, covered, over medium-low heat about 25 minutes. Discard spice bag.
    
4. Pack relish and syrup into 5 hot, clean pint jars, leaving ½-inch headspace. Wipe rims of jars; adjust two-piece metal canning lids. Process in boiling water canner.
    

Results

Cold Spot Location

• The cold spot for this product and jar combination was located at 1½ inches below the center of the jar (Table 1).
• The f(h) value is the number of minutes it takes the straight-line portion of the heat penetration plot to pass through one logarithmic cycle.
• A larger f(h) represents a slower rate of heat penetration.

Thermal Characteristics of Jars Processed by Three Procedures

• The initial canner temperature was consistently maintained at 82.0-82.7°C prior to the loading of filled jars (Table 2).
   
• The initial temperature for this product as prepared and filled into jars by usual home canning practices ranged from 66.0-72.4°C in the standard series.
   
• There was greater variability among initial temperatures in the series used for HFW (overfill) calculations, but this difference did not effect the interpretation of findingsor the ultimate process recommendation.

Effect of Fill Weight

• The heat being applied during the come-up period (time it took the canner to come to a boil) had no effect on jar temperature with the overfill.
   
• Fill weight had a significant impact on both maximum jar temperature obtained as well as the time at boiling required to reach a cold spot temperature of at least 90.5°C for one minute (Tables 2 and 3).
   
• High fill weight significantly increased the f(h), indicating a slower rate of heat penetration (Table 3).

Effect of Initial Jar Temperature

• A decrease of 5°C (69.7, 64.5) in the fill temperature resulted in no difference in either maximum jar temperature reached at the end of the come up period or the 35 minute boiling process (Table 2).
   
• A 5°C decrease in fill temperature did not significantly change the number of minutes at boiling for the cold spot to reach 90.5°C (Table 3).
   
• When a worst-case scenario approach is used there was a slight increase in the time at boiling needed to reach a cold spot temperature of 90.5°C in lower initial temperature jars (16 min. vs. 14 min.).
   
• In practice, this finding would result in a longer recommended process time for the low initial temperature jars. Home canning recommendations are rounded up to the next 5-minute interval. The process time in the standard procedure would be 15 minutes; the recommended time for the low initial temperature practice would be 20 minutes.

Summary

• An increase of 118 grams solids per pint jar significantly increased the heat penetration rate (fh) and more than doubled the required processing time for this product.
   
• A decrease of 5°C in the initial fill temperature did not change the heat penetration rate (fh) or processing time for this product.
   

Implications for Future Research and Practice

• Canning instructions should specify a minimum number of jars to the recipe to avoid overfills.
   
• It is possible that the recommended process time could be reduced if lethality during the cooling period is considered. Additional data would need to be collected to determine maximum jar temperatures reached with less than 35 minutes of boiling.
   
• Results are limited to jar size and shape (conformation) used in this study.
   
• If sensory evaluation testing in the future recommended any changes in the recipe that increased the equilibrium pH, heat penetration data and processing recommendations would need to be re-evaluated.
   

References

1. Andress, E.L. 2001. A national survey of current home canning practices in the U.S. Athens, GA: National Center for Home Food Preservation, Department of Foods and Nutrition, The University of Georgia, Unpublished data.
    
2. Davis, C.A. and Page, L.1979. Practices used for home canning of fruits and vegetables. UDSDA Home Econ. Research Report, No. 43. Washington, DC: Government Printing Office.
    
3. Garner, H. H. and Andress, E.L. 2001. Effect of marinating procedure on pH of a pickled jicama relish. Undergraduate research study, Athens, GA: Department of Foods and Nutrition, The University of Georgia. Unpublished data.
    
4. Statistical Analysis Software, v. 8.2 2001. Cary, NC: SAS Institute Inc.
    

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Garner H.H. and E.L. Andress. 2002. Effect of Fill Weight and Initial Temperature on Processing Time for a Home Pickled Jicama Relish. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Description of Income Distribution Chart.

This chart is a pie graph representing the percentage of respondents who fall into different levels of income distribution (i.e. < $15k, $15-$25K, $25-$35K, etc.). Below is a tabular representation of this data based on actual numbers not percentages.

Back to Current Home Canning Practices in the U.S.

Description of Educational Level Chart.

This chart is a pie graph representing the percentage of respondents who completed various levels of education (i.e. GED, 4 year degree, post graduate, etc.). Below is a tabular representation of this data based on actual numbers not percentages.

Back to Current Home Canning Practices in the U.S.

Description of Figure 1.

Figure 1 is a bar chart that shows results from the survey. The graph shows the percentage of respondents that used the following packaging material categories: freezer paper, aluminum foil, plastic bags, plastic containers, plastic wrap, glass jars, and other. Results were divided by food types: fruit, vegetables, repackaged non-meat items, repackaged meats, and fresh meats. Below are the results in tabular format.

Back to Current Home Canning Practices in the U.S.

E. L. Andress1, E. M. D’Sa2, M. A. Harrison2, W. L. Kerr2, J. A. Harrison1, and B. A. Nummer1. (1) Department of Foods and Nutrition, 208 Hoke Smith Annex, (2) Department of Food Science and Technology, The University of Georgia, Athens, GA 30602.

Paper 46B-2. Presented at the Institute of Food Technologists Annual Meeting, Anaheim, CA, June 17, 2002.

Abstract

Freezing food is an easy and popular method of home food preservation. Improper practices can lead to poor food quality and satisfaction as well as economic losses. Educational efforts and publications for the home food preserver need to be targeted toward the interests and practices of today's consumer. The objective was to conduct a national survey of households that routinely practice home freezing preservation of foods, to determine the level of activity and types of practices. A series of 42 close- or open-ended questions were answered by 473 adults in a national telephone interview conducted by the Survey Research Center, University of Georgia from October 24, 2000 to January 10, 2001. Questions included respondent's source of freezing instructions, types and quantities of foods frozen, blanching methods, packaging materials used, food spoilage and demographic information. A freezer separate from the refrigerator/freezer is maintained by 53% of respondents, most commonly in a basement. Vegetables are frozen by 43%, seafood by 36% and fresh fruits by 31%. Fresh meat, mainly beef, is repackaged and frozen by 76%. Foods other than meats are repackaged and frozen by 49%. One in four report blanching food before freezing. Plastic bags are the most preferred packaging method, followed by plastic containers. Over 90% reported that the foods they froze did not spoil. Food freezing instructions were obtained from family or friends by 29% of respondents and from cookbooks, magazines or newspapers by 15%. A significant number (25%) obtained instructions from 'other' sources that included 'common sense'/general knowledge. Public awareness of the Extension Service and USDA as a source of home food freezing recommendations could be improved. Significant activity in freezing fresh foods as well as repackaging of purchased foods indicates that consumer information on packaging techniques and other practices for preserving quality is important.

Introduction

Home preservation of foods, including home freezing, has always been popular, being traditionally used to process and preserve seasonal, surplus or economically available foods for use in off-peak seasons or through the year. Early household refrigeration and freezing methods relied on the use of iceboxes (6), but the introduction of mechanical refrigeration in the late 1800s stimulated the cold-preservation of foods. The earliest commercially available household refrigerators were demonstrated by General Electric in 1911 and electric refrigerators with freezers were available to the public in the 1920s and 1930s, though mass production of refrigerators did not begin until after World War II (7). The 1940s and 1950s witnessed the birth of several innovative commercial frozen foods and techniques and rapid growth in frozen food storage. In the 1950s, USDA began publishing scientific research on methods in home freezing. Later, data from the FDA confirmed that frozen fruit and vegetable products have equivalent or superior nutrient profiles as compared to their fresh counterparts (8).

Appropriate methods yield high quality frozen foods. Home freezing is deemed 'slow-freezing', where the target temperature is achieved in 3-72 h (3). Attention to all steps in the freezing process is essential to maintain the desired appearance, consistency, microbiological and nutritive quality, and shelf life of the frozen food. They include pre-freezing food preparation (blanching or anti-discoloration treatments, choice of freezing materials), achieving a fast rate of freezing, a constant freezer temperature, and suitable thawing procedures. Improper practices can lead to poor food quality and economic losses, as well as food safety concerns.

Surveys conducted earlier on home-freezing practices date back to 1964 and 1976 (1). Knowledge of contemporary consumers' home-freezing practices would be helpful in understanding current family food management practices, the extent to which traditional freezing recommendations are still being adopted, and gaps in consumers' knowledge of recommended practices. An additional aim of this national survey was to identify potential areas of research, in order to update home freezing recommendations based on sound scientific principles.

Objectives

• To determine the current level of home freezing activity in the U.S.
• To determine the most frequently home frozen food products and techniques used in household freezing of food.
• To identify topics and practices for research on home freezing practices.

Methodology

The National Center for Home Food Preservation (NCHFP), in conjunction with the Survey Research Center (SRC), University of Georgia, Athens, conducted a national telephone survey of adults from randomly selected households across the nation, between October 24, 2000 and January 10, 2001. A 42-item survey instrument which included 16 open-ended questions was developed by the NCHFP and refined with the assistance of the SRC. Structuring and supervision in an interviewer's work is essential in order to gather data in a controlled and standardized fashion (4). Thus, interviewers trained in survey research and telephone-interviewing technology by the SRC were used for the interviewing. Appropriate supervision (one-fifth to one-quarter of all interviews were monitored) during interviews helped maintain quality control. 1244 eligible respondents were contacted; these yielded 473 complete interviews. For several questions, in addition to selecting a 'first-choice' response, respondents were provided with the option of selecting more than one choice as their 'second-choice, third-choice' etc. responses. Probability analyses estimated that the number of interviews conducted were more than sufficient to achieve the target levels of precision and accuracy in drawing conclusions on population responses based on sample estimates (5).

Results

Freezing instructions:  Of a total of 501 interviews conducted, 473 respondents (94.4%) reported freezing foods in their household, other than those purchased in the supermarket. The sources of freezing instructions were as follows:

Where is the freezer?  53% respondents possess a freezer that is separate from their refrigerator, located:

• in the basement (34%), garage (26%), kitchen (15%), laundry room (8%), porch (4%).
   
• 'Other' locations for the freezer include, the dining room (4 respondents), utility room (5), outside shed (10), storage room (5), and one each in a bedroom, carport, pantry or pool house.
   

The ideal location for a freezer is a well-ventilated room near the kitchen, with ambient temperatures between 50-65°F, away from direct sunlight. Contrary to popular thought, keeping the freezer in a cold place does not increase efficiency. This is particularly significant in areas experiencing several months of below-freezing temperatures where an unheated garage is not an ideal location (2).

What is being frozen and by how many?

Packaging materials:  Fig.1. represents the types of packaging materials used for freezing various food categories.

Plastic bags were also the packaging material of choice for seafood, followed by freezer paper (16%), plastic wrap (13%), plastic containers (11%) and aluminum foil (9%).

How much is being frozen?

Pre-freezing preparation

Blanching is an important pre-freezing step for some foods that ensures the inactivation of enzymes and fixing of green color of vegetables, among other functions. Approximately one in four respondents reported that they blanched mainly vegetables in preparation for freezing, in boiling water (86%), using steam (7%) or in a microwave (6%).

Spoilage of frozen foods

Only 7% (33 respondents) reported spoilage of the food that they froze, the indicators of spoilage being freezer burn (18 respondents), thought that it was left in the freezer too long (8), tasted bad, looked brown, broken seal, packaged improperly, and 'power was out for several days' (one each).

Demographic analyses

• 74% respondents were female, 71% were located in metropolitan areas, and the majority belonged to the 35-49 age category (32%), followed by the 25-34 and 50-64 (20% each) categories.
   
• 67% were employed at some time in the preceding 12-month period and 73% of these worked year-round.
   
• 32% respondents lived in 2-person households, 58% of households had all individuals over 18.
   
• 78% respondents were White, 9% African-American, 5% described themselves as 'multi-racial', 2% Asian/Pacific Islander and 1% Native-American.
   
• The largest number of respondents was from the South (34%), followed by the North Eastern (26%), North Central (23%) and Western (17%) regions.
   
• Educational level and income distribution of respondents are represented in the following figures.

Summary

• A high proportion of respondents (94.4%) reported home freezing some type of food item.
   
• Only 1% respondents made use of USDA or Extension Service publications as their source of freezing instructions - methods to disseminate and emphasize use of this readily available, research-based resource should be investigated.
   
• Plastic bags are the most frequently used packaging material of choice for freezing most food items. Emphasis should be placed on selection of the recommended type of freezer plastic bag for home food preservation purposes.
   
• Only one in four respondents reported using blanching as a pre-freezing technique. Use of these techniques, however, should be emphasized to ensure highest frozen food quality and shelf life.
   
• Regional differences in freezing practices were observed, ranging from 17% of respondents from the Western region, to 34% respondents located in the South. Approximately three out of four respondents were female, and residing in metropolitan areas.
   
• Approximately two out of three respondents interviewed were employed, approximately one out of three was either a High School graduate or had some college education or technical degree.
   
• Among those choosing to reveal their income level, the highest percentage (17%) of respondents belonged to the 50-75K- income group.
   

References

1. Hatfield, K. M. 1981. Changing home food production and preservation patterns. National Food Review 27:22-25.
2. Hodges, M. 1984. Rodale's Complete Book of Home Freezing. Rodale Press, Emmaus, PA.
3. Jay, J. M. 2000. Low-temperature food preservation and characteristics of psychrotrophic microorganisms. In Modern Food Microbiology, 6th Edition. Aspen Publishers Inc., Gaithersburg, MD. p. 323-339.
4. Lavrakas, P. J. 1987. Telephone Survey Methods: Sampling, Selection and Supervision. Applied Social Research Methods Series, Volume 7. SAGE Publications, CA, U.S.A.
5. Bason, J. 2001. Materials and methods statement. Survey Research Center, The University of Georgia, Athens, GA.
6. Rogers Refrigeration. Refrigeration history. Available at http://www.rogersrefrig.com/history.html. Accessed on June 9, 2002.
7. Association of Home Appliance Manufacturers. 2001. History of the refrigerator. Available at http://www.historychannel.com/exhibits/modern/fridge.html. Accessed on June 9, 2002.
8. American Frozen Food Institute. 2000. History of frozen food. Available at http://inventors.about.com/gi/dynamic/offsite.htm?site=http://www.affi.com/factstat%2Dhistory.asp. Accessed on June 9, 2002.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Andress, E.L., E.M. D'Sa, M. A. Harrison, W. L. Kerr, J. A. Harrison, and B. A. Nummer. 2002. A survey of practices in freezing foods at home in the U.S. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Description of Figure 5.

Figure 5 is a vertical bar chart showing the percentage of respondents in the survey who canned foods in two categories: fruits (including tomatoes) and vegetables. The information is provided below in a tabular format.

Back to Current Home Canning Practices in the U.S.

Description of Figure 4.

Figure 4 is a vertical bar chart showing the percentage of respondents in the survey at various income levels. The information is provided below in a tabular format.

Back to Current Home Canning Practices in the U.S.

Description of Figure 3.

Figure 3 is a vertical bar chart showing the percentage of respondents in the survey with various numbers of household members. The information is provided below in a tabular format.

Back to Current Home Canning Practices in the U.S.

Description of Figure 2.

Figure 2 is a pie chart showing the percentage of respondents in the survey at different educational levels. The information is provided below in a tabular format.

Back to Current Home Canning Practices in the U.S.

Description of Figure 1.

Figure 1 is a pie chart showing the percentage of respondents in various age groups in the survey. The information is provided below in a tabular format.

Back to Current Home Canning Practices in the U.S.

E. L. Andress1, E. M. D'sa, M. A. Harrison, W. L. Kerr, J. A. Harrison, and B. A. Nummer. (1) Dept. Foods and Nutrition Extension, University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602, (2) Dept. Food Science and Technology, University of Georgia.

Paper 46B-3. Presented at the Institute of Food Technologists Annual Meeting Anaheim, CA, June 17, 2002.

Abstract

Home canning is a traditionally popular means of preserving seasonal produce or specialty foods. The last comprehensive survey of practices conducted by USDA was in the 1970s. Significant lapses in appropriate techniques were documented and later survey reports by others have not revealed major shifts toward improved practices. Computer listservs and the large commercial book industry have the potential for more widespread sharing of traditional and possibly unsafe techniques than ever before.

The objective was to conduct interviews with individuals primarily responsible for household food preparation, to determine their activity level in home canning and use of critical safety practices.

Between October 24, 2000 and January 10, 2001, trained interviewers at the Survey Research Center, University of Georgia, recorded 135 complete telephone interviews from households randomly selected across the nation. The 38-item interview included questions about the respondent's source of canning instructions, methods used, types and quantities of foods canned, containers and equipment used, equipment testing procedures, success of canning procedures and spoilage.

Survey results indicated that friends or relatives (48%) and cookbooks (19%) were the most popular sources of canning instructions. Vegetables were canned by 71%; tomatoes/tomato products by 60%; and fruits by 47%. The boiling water canner was the most frequently used processing method with 58% and 39.5% using it to can fruits (including tomatoes) or vegetables respectively. A pressure-based canner was used by 34% and 49% using it to can fruits or vegetables respectively. Only 24% had the dial gauge on their pressure canner tested. Recommended jars were used by 74%. Only 5.2% reported spoilage of home canned foods.

Greater adoption of science-based home canning techniques is still needed by consumers, particularly in the selection of appropriate processing temperatures, equipment and supplies. Findings document practices and knowledge that should be targeted in educational programs.

Introduction

Home canning has been a popular means of preserving seasonal produce or specialty foods for over a century. The level and type of related activity has shifted up and down throughout this time due to society and family economic conditions, war efforts, weather conditions and interest in duplicating what is available in the commercially processed food supply. Many of today's home canners are interested in being creative and view home canning as an art as much as a science (4). Though diverse recipes provide variety to people, the maintenance of safe practices in canning cannot be over-emphasized. If done improperly, home canning can lead to foodborne illness and even death, as well as economic losses from spoiled food.

Since the late 19th century, the USDA has published recommendations for home canning processes, pickling of foods, and sugar concentrates (jam and jelly products). Since that time the public as well as the Cooperative Extension System and home canning equipment manufacturers have continued to rely on the USDA for guidance. Scientifically-based methods for control of bacteria and calculation of sterilization processes for canned foods were developed in the first part of the 20th century. These methods and later refinements have been applied to the science of USDA home canning recommendations since the mid-1940s.

The number of books on home preserved specialties in the commercial printing industry, prevalence of listservs and other internet-based sharing of home canning directions, numbers of individual inquiries received by the Cooperative Extension System and other indicators support the fact that there are active home canners today (4). A review of these same sources, however, reveals that there is also transfer of non-scientific or high-risk directions for home canning and processing of foods occurring frequently.

The last comprehensive surveying of home canning practices conducted by USDA was in the 1970s (1,3). Significant lapses in appropriate techniques were documented at that time. More recent information about home canning practices has only been obtained from other sources in limited amounts (2,4). Because there is evidence that people are canning food at home (2,4) but there is little recent documented information on their actual practices, a national survey seemed in order.

Objectives

To conduct a national survey of U.S. households routinely practicing food preservation techniques:

• To determine the extent of current home canning activity;
• To identify contemporary home canning techniques being practiced, as well as types and quantities of foods being canned;
• To identify risky practices requiring attention by educators and researchers.

Methodology

The National Center for Home Food Preservation (NCHFP) at The University of Georgia (UGA) developed a questionnaire and contracted with the Survey Research Center at UGA to conduct a national telephone survey. The survey instrument was comprised of 38 closed or open-ended (5) questions aimed at obtaining detailed information about individuals' home canning practices plus additional questions on home freezing practices. Respondents were provided with the option of choosing more than one appropriate response for some questions. The study conducted 501 interviews from randomly selected households across the nation, with all households having a near-equal chance of being selected for inclusion in the sample. Between October 24, 2000 and January 10, 2001, a total of 5,259 numbers were called; and 1,244 eligible adult interviewees were contacted. The final cooperation rate was 40.3% (501 interviews). The 501 interviews yielded 135 complete interviews of those canning food at home. To insure quality control of the interviewing process, interviewers were trained, and approximately one-fifth to one-quarter of the interviews were monitored, thereby eliminating interviewer errors.

Results

Who is canning?

Figure 1. Age distribution of respondents in years

Figure 2. Educational level of respondents

Figure 3. Size of households with home canners

Figure 4. Annual income level of respondents

• 27% of individuals contacted in the survey reported canning food at home in the previous year; 91% of these said that they planned to can food the following year.
• Only 10% of these home canners canned extra food in preparation for Y2K; those who did canned beans, tomatoes, vegetables, fruit and jams.
• About half of home canners are between 35-64 years of age; 23% are 65 and over, and 24% are under 35 (Figure 1).
• 82% of respondents were female, 56% were from Metropolitan statistical areas, and 52% were employed during the preceding year, either year-round (72%), for 26-51 weeks (21%) or for less than 26 weeks (4%).
• Most home canners have at least a high school education; 28% have at least a 4-yr college degree (Figure 2).
• More than half of home canners live in 2-4 person households (Figure 3). 60% of these households had no individual under the age of 18-yrs, while 19% had one under-18 yr old, and 8% had either 2 or 3 under-18s.
• Participation in home canning does not appear to be related to income, but there was a fairly high non-response rate to this question (Figure 4).
• 84% of respondents were 'White', 6% African-American, 2% each Asian/Pacific-Islander or Native American and 4% described themselves as multi-racial.
• 39% of respondents were located in the South, 30% in the North East, 18% in the North Central region and 13% in the West.

What are their sources of information?

• About half obtain their canning instructions from friends or relatives (Table 1):


• The 'other' sources included canning books (6 respondents), instructions that came with the purchase of fruit (1 respondent) and the internet (1 respondent).
• 67% of respondents used their canning instructions 'as is', while 29% adapted the instructions for their individual use.

What are they canning and how?

Figure 5. Methods used to can fruits and vegetables

• 71% canned vegetables, 60% canned tomatoes/tomato products and 47% respondents canned fruits. Figure 5 represents the canning methods used by respondents who canned fruits (including tomatoes) and vegetables.


• Table 2 represents the types and quantities of food items canned.

Equipment Use and Management

• Approximately one out of four respondents who used a pressure canner (n=54), had the dial gauge tested in 1999. Eleven percent have a pressure canner without a dial gauge.
• One out of every five using pressure canners (n=54) reported making elevation adjustments in processing, and 12% (n=69) of those using boiling water canners made elevation adjustments. Approximately 11% and 15% (for pressure/boiling water, respectively) reported that such adjustments were not necessary.

Jars and Lids

• Approximately 74% used home canning jars with 2-piece lids, 17% used recycled jars from commercially canned foods (e.g., peanut butter, salad dressing jars), and 14% used older-type home canning jars with rubber rings. 4% of respondents used metal cans.
• 38% of respondents reported jars that did not seal properly after the canning process.
  • 13 people reported one improperly sealed jar, 10 reported two.
  • Individuals with improperly sealed jars (n=51) either discarded the food in these jars (41%), refrigerated them and consumed the food quickly (29%) or reprocessed them (24%). Only one respondent reported freezing the contents of the improperly sealed jars.

Food Storage and Use

• In response to a question posed about whether home- or commercially-canned foods could be spoiled without any visible sign of spoilage, 53% replied in the affirmative.
• 93% respondents reported no spoilage in their home-canned foods. Among the seven respondents who did report spoilage, the items involved were pickles, marinated/pickled peppers and vegetables (two respondents each).

Summary

• Greater adoption of science-based home canning techniques by many home canners is needed.
• Little can be discerned about the science base of many instructions being used, as family and friends are cited as the source. It was not determined what the ultimate sources of those directions are. The USDA and Extension Service do not have large recognition as the cited source, although it is possible that family, friends, cookbooks and manufacturers are using the same instructions. The fact that 29% feel free to adapt the instructions they do have could be cause for concern, also.
• One finding of greatest concern is the lack of pressure-based processing temperatures for low-acid foods. This survey did not determine if correct time/temperature combinations are being used for all foods, but the fact that vegetables are being canned at boiling water temperatures or without any processing (open-kettle) is enough to know those people are at high risk for foodborne illness, including botulism.
• Altitude adjustments in processing temperatures or times are most likely not always being made when necessary.
• Findings document risky practices and knowledge that should be targeted in educational programs and publications.

References

1. Davis, C.A., and L. Page. 1979. Practices used for home canning of fruits and vegetables. USDA Home Economics Research Report No. 43. Washington, DC: Government Printing Office.
2. Getty, V. and Evers, B. 1997. Activity profile of home canners. Electronic Food Rap, Vol. 7(40). http://www.sfu.ca/~jfremont/homecanning.html. Accessed on June 1, 2002.
3. Hatfield, K.M. 1981. Changing home food production and preservation patterns. National Food Review 27:22-25.
4. National Center for Home Food Preservation. 1999. Information collected from the Cooperative Extension System, cookbooks and internet. Unpublished data. Athens, GA: The University of Georgia.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Andress, E.L., E.M. D'sa, M.A. Harrison, W.L. Kerr, J.A. Harrison and B.A. Nummer. 2002. Current home canning practices in the U.S. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

The Use of Microwave Blanch Technology as an Alternative Preparation Method for Freezing Collard Greens (Brassica olteracea) at Home

J. ROBERTS, L. T. Walker and J.C. Anderson

Dept. of Food & Animal Sciences, Alabama A&M Univ. P.O Box 1628, Normal, AL 35762-1628
This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Presented at the Institute of Food Technologists International Food Safety and Quality Conference and Expo, Orlando, FL, November 6, 2003.

Abstract

Most home food preservers do not realize that microwave blanching is an option when preparing fresh vegetables for frozen storage. Previous research indicated that microwave blanching may be the best method for maintaining nutrients and physical attributes when preserving vegetables for home freezing. Thus far, only lower wattage microwave blanch research has been conducted on selected vegetables. Further studies are necessary to determine the effect of the higher wattage microwave effects of vegetables.

The objective of the study was to determine if microwave blanching, using varying wattages, is a suitable alternative method for preparing collard greens (Brassica oleracea) for home freezing.

Freshly harvested collard greens (CG) were blanched for 3 min in covered containers using: boiling water (BW), steam (ST) and three different wattage microwaves including 1000 watt (MW1), 1200 watt (MW2), and 1300 watt (MW3). Samples were ice-cooled, placed in freezer bags, and stored at -18oC for 6 months. Enzyme activity (peroxidase and lipoxydase) and physical parameters (moisture, texture and color) were measured prior to blanching, immediately following blanch treatments and after 4 and 6 months of frozen storage. Retention of ascorbic acid (AA), calcium (Ca), iron (Fe) and potassium (K) and sensory characteristics were assessed after 6 months of frozen storage.

Peroxidase activity (POD) was reduced from 0.3-0.35 units in fresh, unblanched samples to 0.001-0.028 units in blanched CG. Lipoxydase activity (LOX) was reduced from 6160-6700 units in fresh, unblanched CG to 2410-4370 units in blanched samples. These enzymes when active catalyze the oxidative deterioration of vegetables. All blanching methods increased greenness of samples. Moisture content for the blanched samples averaged 78% for all treatments, except BW which averaged 61%. No significant moisture difference (p>0.05) was found among the MW1, MW2, MW3 and ST treatments. Texture (maximum force) was lowest at 757 N for the BW treatment and highest for ST blanched treatment (1605 N). Lower texture values can be attributed to a greater cooking effect for the BW treatment. There was no significant texture difference (p>0.05) among the microwave t treatments. The MW1 treatment retained the highest percentage (93%) of ascorbic acid (32.9 mg/100g). The BW treatment had the largest (47%) ascorbic acid loss (16.8 mg/100g) due to leaching effects. No significant difference in ascorbic acid retention (p>0.05) among the microwave treatments was observed. The MW3 treatment retained 92% Ca (4474 mg/kg), 81% Fe (145 mg/kg) and 96% K (2310 mg/kg) which was significantly better than any other blanching treatment. Sensory evaluation (multiple comparison ranking) tested preference using frozen commercial collard greens as a control versus the 5 blanch treatments. There were no significant differences among the treatments for preference.

The study indicated that the overall quality of MW blanched collard greens (for all three wattages) was as good as or superior to BW and ST blanched vegetables. Further, it was also ascertained that MW blanching is a suitable alternative to ST or BW blanching when preparing vegetables for home freezing.

Introduction

Vegetables require a short heat treatment or blanching to inactivate enzymes and stabilize quality prior to and during frozen storage. Conventional blanching processes using boiling water or steam as a heating medium results in leaching of solids and an ultimate loss of nutrients. A more gentle blanching process involving microwave technology, which has a more efficient heating system, could have positive effects on the quality of the finished product.

Most home food preservers do not realize that microwave blanching is an option when preparing fresh vegetables for frozen storage. Previous research indicates that microwave blanching may be the best method for maintaining nutrients and physical attributes when preserving vegetables for home freezing. Thus far, only lower wattage microwave research has been conducted on selected vegetables. Further studies are necessary to determine the effect of the higher wattage microwave effects on blanching of vegetables.

Objective

The objective of this study was to determine if microwave blanching, using varying wattages, is a suitable alternative method for preparing collard greens for home freezing.

Materials and Methods

Sample Preparation

Fresh collard greens were harvested fresh in late September (approximately 75 days of age). Four harvests were conducted. The greens were rinsed three times with tap water to remove dirt and debris, blanched, and analyzed within 4 hr of harvest. Three different blanching methods were applied to 200g samples for 3 min in covered containers. The methods included BW (1900 mL), ST (300 mL water), and MW1, MW2, & MW3 (60 mLwater for each MW treatment). Blanching time and proportion of vegetable/water were based on average times for BW and ST recommendations. A 3 min MW blanch time was established in a previous study. This was the time required to inactivate POD activity. The greens were allowed to sit an additional 1 min following treatment, then ice-cooled for 5 min and drained. Samples were removed and packed in 1 L plastic bags.

Analyses

Peroxidase and lipoxydase activity, moisture content, texture, and color were measured prior to blanching, immediately following blanch treatments and after 4 and 6 months of frozen storage. Sensory characteristics and retention of ascorbic acid (AA), Ca, Fe, and K were assessed after 6 months of frozen storage.

Ascorbic acid
AA was determined by HPLC using a UV detector set at 272 nm and oven temperature set at ambient. The analytical column was a 250 x 4.6 mm x ¼ in Valco Microsorb (MV 100-5) column. The mobile phase consisted of 9.5% acetonitrile in DI water, 0.4 L/L ammonium hydroxide, 0.95 g/L hexane sulfonic acid (pH to 2.8 with phosphoric acid) using the method of Russell (1986). Concentration of AA was expressed as mg/100g.

Color
Finely chopped greens were placed into the sample cup (5 cm diameter) of a Hunter spectrocolorimeter (LabScan Color Flex). L (degree of lightness) values were measured after standardizing on a white background for the blanched products (Giese 2001). The color of fresh collard greens was used as a reference.

Lipoxydase activity
LOX activity was determined spectrophotometrically as described by Hamby and Sammuelson (1967) & revised by Sigma-Aldrich (1997). Absorbance (234 nm) was read at 60 sec intervals for 5 min. Enzyme activity was expressed as units/mL enzyme.

Peroxidase activity
POD activity was determined spectrophotometrically as described by Chance and Maehly (1955) & revised by Sigma-Aldrich (1994). Absorbance (420 nm) was read at 20 sec intervals for 5 min. Enzyme activity was expressed as units/mL enzyme.

Minerals (Ca, Fe, and K)
A microwave-assisted acid digestion procedure for preparing samples (based on US EPA Method 3051 for soil analysis and modified for appropriate foods) was used to prepare the vegetable samples for analysis. The digestate was analyzed using Inductively Coupled Plasma (ICP) Spectrometry and concentrations expressed in mg/kg (SW-846, 1994).

Moisture Content
Moisture content of collard greens was gravimetrically determined by drying at 130°C for 1 hr (AOAC 1990).

Sensory
A 30 or more member consumer sensory panel (Alabama A&M University faculty, staff and students) used the Multiple-Paired Comparison Test to evaluate the single attribute, preference. Commercial frozen products were used as controls for this characteristic. Sensory evaluation was conducted only on cooked products after 6 months of frozen storage (Meullenet and Gross, 1999). The results were evaluated using a Friedman-type statistical analysis.

Texture
A TMS-TP Texture press (Model FTA-300 Force Transducer) was used for texture evaluation. Chopped, blanched greens homogeneously filled the test cell (Model CS-2 Thin Blade Shear-Compression) as described by Ponne, 1994. Texture was determined as force/g of sample.

Statistical Analyses

Collard greens were picked in 4 separate harvests (each harvest was considered a replication). The vegetables were divided into 6 portions for each treatment. Each portion was divided into 4 parts: 1 for immediate postblanching analyses; 1 for postfreezing analyses at 4 months; 1 for postfreezing analyses at 6 months and 1 for sensory evaluation. Determination was done in duplicate for each replicate for chemical and physical parameters. Data was subjected to ANOVA (analysis of variance) and significantly different means were separated using Tukey's HSD test.

Results and Discussion

POD enzyme activity in fresh, unblanched collard greens ranged between 0.3-0.35 units and 0.001-0.028 units following blanching (Figure 1) suggesting that MW blanching for all three MW wattages may be better method for POD inactivation.
 

Figure 1. POD Activity of Collard Greens
 

LOX enzyme activity was reduced from 6160-6700 units in fresh, unblanched CG to 2410-4370 units in blanched CG (Fig. 2). These results show that MW blanching, especially MW3, is the better method for inactivating LOX activity.

Figure 2. LOX Activity of Collard Greens
 

Ascorbic acid retention was highest for MW1 (93%, 32.9 g/100g). The BW treatment had the largest AA loss (47%, 16.8 mg/100g) due to leaching of nutrients into the large volume of boiling water. No significant difference in AA retention (p>0.05) among the microwave treatments was observed. See Figure 3.

Figure 3. Ascorbic Acid Retention for Collard Greens
 

Minerals. MW3 treatment retained 92% Ca (4473 mg/kg), 81% Fe (145 mg/kg) and 96% K (2310 mg/kg) which was significantly better than any other blanching treatment (Table 1).

Table 1. Mineral Retention for Collard Greens

Color-degree of lightness (L) values increased greenness of all samples after blanching (Fig. 4).

Figure 4. Color (L values) for Collard Greens

Moisture content for the blanched samples averaged 78% for all treatments, except BW which averaged 61% (Figure 5). This data suggest that the BW method removed more moisture from the sample than the other treatments. No significant difference (p>0.05) was found among the MW1, MW2, MW3, and ST treatments.

Figure 5. Moisture % for Collard Greens

Texture (maximum force) was lowest at 757 N for BW treatment and highest for ST blanched treatment (1605 N). The lower maximum force value for the BW treatment can be attributed to a greater cooking effect. There was no significant texture difference (p>0.05) among the microwave treatments.

Sensory evaluation using multiple comparison ranking tested "preference" using frozen commercial collard greens as a control versus the other 5 blanch treatments. There were no significant differences (p>0.05) among the treatments for preference.

Conclusion

The study indicated that the overall quality of MW blanched collard greens for all three wattages was as good as or superior to BW or ST blanched vegetables. Further, it was also ascertained that MW blanching is a suitable alternative to ST or BW blanching when preparing vegetables for home freezing.

Selected References

• AOAC. 1990. Official Methods of Analysis of AOAC INTERNATIONAL. 1990. 15th Ed., 3rd Rev., secs 963.27.
• EPA Method 3051. 1994. From SW-846 Online. http://www.epa.gov/epaoswer/hazwaste/test/3_series.htm.
• Hamberg, M. and Sammuelson, A.C. 1967. J. Biol Chem. 242:5329.
• Meilgaard, M., Civille, G.V., and Carr, B.T. 1999. Sensory Evaluation Techniques,3rd Ed., CRC Press, Inc., Boca Raton, FL
• Ponne, C.T., Baysal, T., and Yuksel, D. 1994. J. Food Sci. 59 (5), 1037-1041, 1059.
• Russell, L.F. 1986. J. Food Science, 51(6):1567-68.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and Alabama A&M University receive acknowledgment and this notice is included:

Reprinted with permission of Alabama A&M University. J. Roberts, L. T. Walker and J.C. Anderson. 2003. The Use of Microwave Blanch Technology as an Alternative Preparation Method for Freezing Collard Greens (Brassica olteracea) at Home. Normal, AL: Alabama A&M University, Food and Animal Sciences Department.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Partnerships Produce a National Center for Home Food Preservation Research and Education

Andress, E.L., Harrison, J.A, Harrison, M.A., Kerr, W.L. and Nummer, B.A., The University of Georgia, Extension Foods and Nutrition, 208 Hoke Smith Annex, Athens, GA 30602-4356

Galaxy II Extension Professionals Conference, Salt Lake City, UT, September 23, 2003

About Us

The National Center for Home Food Processing and Preservation is a multi-institutional collaboration funded by with funding from the Cooperative State Research, Education and Extension Service, U.S. Department of Agriculture (CSREES-USDA) with the University of Georgia as the primary institution. Scientists from Alabama A&M University and the University of California-Davis are partners. Experts in home food preservation from other U.S. universities and industry comprise an advisory committee.

Interest in home food preservation and processing remains high in the U.S., but methods must be continually evaluated against updated information in food safety. It is critical to provide educators and consumers with access to current science-based information concerning safety and quality issues regarding home processing of food, and to encourage adoption of revised practices. The Center was established to address food safety concerns for those who practice and teach home food preservation and processing methods. Therefore, the Center is creating, gathering, evaluating, and disseminating science-based recommendations and conducting research as needed in support of those recommendations.

The objectives being addressed include:

• updating home food preservation recommendations through critical reviews of existing literature and additional laboratory evaluations;
• development of a National Center website containing Cooperative Extension System recommendations and publications, as well as a new web-based curriculum on home food preservation available nationwide;
• updating recommendations for Master Food Preservers and community cannery settings;
• updating professionals and volunteers in the Extension System with food preservation findings; and,
• production of a video series on home food preservation.

The faculty in the Center receive numerous requests for technical assistance and trainings from many other states as well as the home food preservation industries in the U.S. and Canada. Undergraduate and graduate students at the University of Georgia and Alabama A&M University are receiving educational benefits through their involvement in the research and curriculum development aspects of the Center's activity.
 

Project Team

The University of Georgia

Alabama A&M University

Collaborators

University of California-Davis
Linda Harris, Ph.D., Associate Cooperative Extension Specialist, Food Sciences and Technology
University of Puerto Rico-Mayagüez
Edna Negrón, Ph.D., Professor and Head of Department, Food Science and Technology

Advisory Committee
University/Cooperative Extension
Evelyn F. Crayton, Ed.D., R.D., L.D., Professor and Extension Foods and Nutrition Specialist, Auburn University
Angela Fraser, Ph.D., Assistant Professor and Extension Food Safety Specialist, North Carolina State University
Linda Harris, Ph.D., Extension Food Safety/Microbiology Specialist, University of California_Davis
Virginia Hillers, Ph.D., Professor and Extension, Washington State University
Elizabeth Hoyle, M.S., Professor and Extension Food Specialist, Clemson University
Patricia Kendall, Ph.D., R.D., Professor and Food Safety Extension Specialist, Colorado State University
Karen Penner, Ph.D., Professor and Extension Specialist, Food Science, Kansas State University
Donna Scott, M.S., Food Safety Specialist and Senior Extension Associate, Cornell University
Christina Stark, M.S., R.D., Extension Nutrition Specialist, Cornell University Industry
Judy L. Harrold, Manager, Consumer Affairs, Alltrista Consumer Products Company
Jo Anne O'Gara, Home Economist, National Presto Industries, Inc.

Our Projects

Multiple strategies for making safe food preservation recommendations available are being used: critical literature reviews and publishing of results; original research; updating of existing USDA and Extension consumer publications; and establishing additional distribution channels for dissemination of guidelines, including a new website. The Center's website is the place to find information about the Center's projects and its findings, USDA home food preservation publications, Center publications, links to other Cooperative Extension System publications, multimedia (graphics, animations, slides, and video), and how-to guides. Other programs in development through the collaboration of the Center include a model volunteer-based Master Food Preserver Program, an instructional video series, and an original web-based curriculum on home food preservation. Evaluation strategies have been implemented to assess effectiveness.

Research

• Original research on microbial safety of various home food preservation methods and ingredients.
  • Microbiota of selected herbs and selected spices
  • Heat penetration studies in three sizes of pressure canners
  • Effect of fill weight and initial temperature on heat penetration in a boiling water canned relish
  • Garlic and oil mixtures
  • Curing and sausage making
• Original product and process development for home canned foods.
  • Jicama relish
  • Tomatillo relish
  • Pepper sauces and pickled pepper rings
  • Mango salsa and chutney
  • Pickles with sugar substitutes
  • Tropical fruit jellies
  • Lemon curd
• Developing guidelines for critical controls for home food preservation methods.
  • Curing and smoking of meats
  • Pickling and acidified foods
  • Canning
  • Freezing
  • Jerky
  • Jams/jellies and other sugar concentrates
• Original research on microwave blanching of some vegetables.
   
• Original research to validate processes for community canneries and metal can processes.
   
• Finding, reviewing and synthesizing relevant scientific literature.
   
• Surveys of home food preservation practices and needs assessment with Extension educators.

Outreach/Communications

• Original website - www.homefoodpreservation.com
• CSREES-USDA Complete Guide to Home Freezing
• Updated CSREES-USDA Complete Guide to Home Canning
• Model Master Food Preserver curriculum
• On-line self-study course for educators, volunteers and 4-H members
• Instructional video series
• Workshops for Extension professionals and other educators if requested

Building Linkages

• Developing a network of scientific and educational expertise and identifying the best resources for educating home food preservers
• Working with home canning industry on product development and recommendations
• Working with government agencies to insure consistency of consumer food safety recommendations
• Representing resources of the Cooperative Extension System to the public

www.homefoodpreservation.com

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USDA Complete Guides
National Center for Home Food Preservation
Univ. of Georgia Factsheets and Resources
Features from Other Universities
Other Government Publications

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Tel: (706) 542-3773
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Effects of microwave blanching vs. boiling water blanching on retention of selected water-soluble vitamins in turnip greens using HPLC

M. A. OSINBOYEJO, L. T. Walker, S. Ogutu, and M. Verghese

Dept. of Food & Animal Sciences, Alabama A&M Univ. P.O Box 1628, Normal, AL 35762-1628
This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Paper 92A-8. Presented at the Institute of Food Technologists Annual Meeting, Chicago, IL, July 15, 2003.

Abstract

Blanching is an effective way of preserving fruits and vegetables. However, it has been shown that conventional boiling water blanching of vegetables results in the leaching of water-soluble vitamins. This experiment was designed to determine the effectiveness of different blanching methods on the retention of selected water-soluble vitamins in turnip greens. The objective was to employ a HPLC method in the determination of the level of selected water-soluble vitamins in turnip greens that were blanched using conventional and microwave blanching methods. Turnip greens (Brassica rapa) were purchased from a local supermarket. They were thoroughly washed, chopped and separated into three treatment groups including unblanched (UB) which served as the control; boiling water blanched (BWB); and microwave (1300 watts) blanched (MWB). A 100 gm sample from each treatment group was subjected to blanching treatment (according to designation) for 5 minutes. The samples were cooled in iced-water and an extract prepared using a modification of a method previously described by Russell (1986). A 10µl sample (in duplicate) from each treatment extract was separately injected in a Varian ® HPLC with a C18 column and a UV detector set at 272nm. Concentrations of ascorbic acid, folic acid, thiamin and riboflavin were determined using external standards.

The result showed that, compared to control samples, BWB lost 16% ascorbic acid, and 100% folic acid, thiamin and riboflavin while MWB lost 28.8% ascorbic acid, 25.7% folic acid 16.9% thiamin and 7.2% riboflavin.

The results indicate that MWB is more effective in the retaining the selected water-soluble vitamins with the exception of ascorbic acid. This is also in congruence with earlier findings indication that microwave blanching is more effective in retaining nutrients in vegetables.

Introduction

Blanching is the process of exposing vegetables or fruits to high temperature for a short period of time.  It is done not only to prolong the self-life of vegetables by inactivate the enzymes responsible for browning (lipoxygenase and peroxidase) but also improves both color and flavor. Proper blanching is important as under-blanching is ineffective in inactivating the enzymes that reduce the quality while over-blanching can result in overall quality reduction and the leaching of essential vitamins and minerals. Conventionally blanching is done through the use of boiling water or steam, however microwave blanching may be a suitable alternative which could lead to improved overall quality and retention of essential minerals and vitamins. However the high cost of the equipment made the use uncommon in food industries. Boiling water blanching is most used at home. It is easy, simple and inexpensive, but has highest potential of leaching water-soluble vitamins and minerals compared to other methods. Convectional steam blanching is currently the most commonly used method in the food industry today. It is relatively inexpensive and retains minerals and water-soluble vitamins over-boiling water blanching.

Objectives

• The objective was to employ a HPLC method to determine the level of selected water soluble vitamins in turnip greens blanched using boiling water and microwave.

Materials and Methods

Preparation of samples

Preparation of Mobile Phase

Statistical Analysis

• Turnip greens (Brassica rapa) were purchased from a local supermarket.
• They were thoroughly washed, chopped (approximately 0.5 inches) and separated into three treatment groups.
• From each group 100g samples were separated for microwave blanching (MWB), boiling water blanching (BWB) and control-unblanched (UB).
• Microwave blanching was conducted using a domestic Panasonic Genius microwave with 1300 wattage for 5 min in a 2 quart/2 liter Pyrex container containing 60 ml tap water.
• Boiling water blanching was conducted in a 2 quart/2 liter enamel double boiler containing 1900 ml tap water. Boiling was conducted for 5 min.
• The sample was cooled in iced water and extracted.
• The extract from each treatment and control were prepared by blending 100g in 100g of 6% metaphosphoric Acid for 60 seconds.
• 50g of the sample was mixed with 35ml methanol and centrifuged at 13,300 X G at 4°C for 15mins.
• A10 ml aliquot of the supernatant was diluted to 100ml with 1.5mM pyrogallol and passed through a 0.45µm filter.
• A10µl of each extract was separately injected into a Varian HPLC with a C18 column with a mobile phase flow rate of 2ml/min and detected using a UV detector set at 272nm.
• 1mg of each vitamin was diluted with1000µl of mobile phase and 10 µ l was injected in the HPLC for analysis.
• 9.5% acetonitrile in water containing 0.4µl NH4OH (Ammonium Hydroxide) and 0.9 of hexane sulphonic acid pH adjusted to 2.8 with 85% of phosphoric acid.
• Data were analyzed by ANOVA, and differences in means were determined using Tukey's studentized range tests with SAS statistical program, 2001, Version 8. Differences were considered significant at P0.05.

Results and Discussion

• The results showed that boiling water blanching lost 99.9% ascorbic acid, 100% folic acid, thiamine and riboflavin while microwave blanching lost 28.8% ascorbic acid, 25.7% folic acid, 16.9% thiamine and 7.2% riboflavin when compared to control.

Figure 1: A comparison of retention of water soluble vitamins in turnip greens blanched in boiling water vs. microwave blanching

Table 1: Effect of microwave blanching vs. boiling water blanching on water soluble vitamin content on turnip greens (mg/100g)

	Ascorbic Acid	Folic Acid	Thiamine	Riboflavin
Control	20.0	536.0	3.06	14.0
Microwave blanching	14.2	398.0	2.54	13.0
Boiling water blanching	0.17	0.01	0.01	0.01

Conclusion

• The results indicate that Microwave blanching was more effective in retaining water-soluble vitamins in turnip greens. This is also in congruence with earlier findings indicating that microwave blanching is more effective in retaining nutrients in vegetables compared to conventional blanching methods.

Selected References

• Frank L. Vandemark (1981). Analysis of Water-Soluble Vitamins. J. Liquid chromatography. Vol. 4: 1157 Liquid Chromatography Applications
• Laurence L. Saettel (2000) Turnip Brassica rapa.
• (www.dietobio.com/aliments/en/turnip.html)
• Owen R. Fennema. (1996) Food Chemistry 3rd Edition Marcel Dekker, Inc. pp 541, 543, 561, 577
• Russell, L.F.(1986) High Liquid Chromatographic Determination of Vitamin C in Fresh Tomatoes. J. Food Science. Vol.51, No 6: 1567

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and Alabama A&M University receive acknowledgment and this notice is included:

Reprinted with permission of Alabama A&M University. M. A. OSINBOYEJO, L. T. Walker, S. Ogutu, and M. Verghese. 2003. Effects of microwave blanching vs. boiling water blanching on retention of selected water-soluble vitamins in turnip greens using HPLC. Normal, AL: Alabama A&M University, Food and Animal Sciences Department.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Description of Botulism from Home Canned and Processed Foods, 1970-80 Graph.

This bar graph chart shows results from the survey. The graph shows the number of cases and outbreaks for each year. Below are the results in tabular format.

Back to National Center for Home Food Preservation paper

E. L. Andress. Department of Foods and Nutrition Extension, University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602-4356.

Paper 25-4. Presented at the Institute of Food Technologists Annual Meeting, Chicago, IL, July 13, 2003.

Abstract

Home food preservation remains a popular cultural activity. It is critical that those who practice preserving and processing foods at home have access to the most reliable information available concerning food safety and food quality. The National Center for Home Food Processing and Preservation (NCHFP) was established with funding from the Cooperative State Research, Education and Extension Service (CSREES-USDA) in 2000 as a multi-institutional effort with The University of Georgia and Alabama A&M University as the primary institutions. Expert scientists in home food preservation from industry and eight other U.S. universities comprise an advisory committee for the Center.

The Cooperative Extension System (CES) and USDA have a long history of being recognized as credible sources for science-based recommendations; however, a recent survey by the Center revealed that USDA and the CES were no longer being cited as primary sources of instructions for home canning and freezing. The same survey also revealed that a high percentage of home food processors are using practices that put them at risk for foodborne illness and economic losses due to food spoilage.

The Center is conducting outreach activities and research in food microbiology and food quality, in the validation of new and existing preservation methods. The objectives being addressed include: (1) updating home food preservation recommendations based on critical reviews of existing literature and additional laboratory evaluation and scientific validation; (2) development of a National Center website (www.homefoodpreservation.com) containing USDA, NCHFP and CES recommendations and publications, as well as a new web-based curriculum on home food preservation; (3) updating professionals and volunteers in the Extension System with food preservation findings; and, (4) production of a video series on home food preservation. University undergraduate and graduate students are receiving educational benefits through their involvement in the research and curriculum development aspects of the Center's activity.

Summary

• Greater adoption of science-based home canning techniques by many home canners is needed.
• Little can be discerned about the science base of many instructions being used, as family and friends are cited as the source. It was not determined what the ultimate sources of those directions are. The USDA and Extension Service do not have large recognition as the cited source, although it is possible that family, friends, cookbooks and manufacturers are using the same instructions. The fact that 29% feel free to adapt the instructions they do have could be cause for concern, also.
• One finding of greatest concern is the lack of pressure-based processing temperatures for low-acid foods. This survey did not determine if correct time/temperature combinations are being used for all foods, but the fact that vegetables are being canned at boiling water temperatures or without any processing (open-kettle) is enough to know those people are at high risk for foodborne illness, including botulism.
• Altitude adjustments in processing temperatures or times are most likely not always being made when necessary.
• Findings document risky practices and knowledge that should be targeted in educational programs and publications.

Modern Methods of Home Food Preservation

• Canning
• Freezing
• Drying
• Pickling
• Sugar concentrates
  • jams, jellies, butters, preserves, etc.
• Curing, smoking

USDA Historical Support

• USDA has history of making canning recommendations.
  • Canning - series of Farmers Bulletins
  • Began 1909; ran through 1942.
  • WW I - Can the Kaiser
  • WW II - Victory Gardens

USDA Home Canning History

USDA Historical Support

• USDA Complete Guide to Home Canning
  • Superseded four H&G Bulletins
  • 1988, 1989, 1994
  • Collaboration with the Cooperative Extension System (Penn State University).


• Complete Guide to Home Freezing
  • Drafted in 1990's; not published.

Cooperative Extension System

• USDA history interwoven with the land-grant agriculture colleges and universities system.
  • Experiment Stations conducted/conduct research.
  • Cooperative Extension Service - teaching of methods and distribution of USDA publications.
  • More recently integration of applied research and outreach.
    • 1980's - Center of Excellence at Penn State.
    • Current - National Center, multi-state.

National Center for Home Food Processing and Preservation

• Funding from the CSREES-USDA (2000-2004).
  • Cooperative State Research, Education and Extension Service
  • National Integrated Food Safety Initiative
  • Priority issues in food safety best solved using an integrated approach.
  • Support multi-state, multi-institutional, multi-disciplinary, and multi-functional research, extension, and education activities.

National Center for HFP

• Established to provide an integrated research, Extension and education approach.


• Support for the USDA and the Cooperative Extension System with current, reliable and scientifically-validated guidelines on home food preservation.


• Components:
  • Updating USDA-CSREES canning and freezing publications;
  • Applied research to develop new products and validating or adapting older methods;
  • Dissemination methods for recommendations, emphasizing the Cooperative Extension System resources.
  • Educating a "new generation" of students and teachers.

National Center for Home Food Processing and Preservation

• The University of Georgia - Lead Institution
  • Department of Foods and Nutrition
  • Department of Food Science and Technology
  • Department of Housing and Consumer Economics


• Alabama A&M University - 4-yr Partner
  • Department of Food and Animal Sciences


• University of California-Davis - 2-yr Partner
  • Department of Food Sciences and Technology


• University of Puerto Rico-Mayagüez
  • Department of Food Science and Technology

University of Georgia Team

• Foods and Nutrition
  • Dr. Elizabeth Andress, Principal Investigator
  • Dr. Judy Harrison, Co-PI
  • Dr. Brian Nummer, Project Coordinator
  • Dr. Elaine D'sa, Research Coordinator
  • Jimmy Hansen, Web Site Administrator


• Food Science & Technology
  • Dr. Mark Harrison, Co-PI
  • Dr. William Kerr, Co-PI
  • Dr. Sung-Gil Choi, Lab Technician


• Housing and Consumer Economics
  • Dr. Anne Sweaney, Team Member

Alabama A&M University Team

• Food and Animal Sciences
  • Dr. Lloyd Walker, Principal Investigator
  • Dr. John Anderson

Other Collaborators

• University of California-Davis
  • Dr. Linda Harris


• University of Puerto-Rico, Mayagüez
  • Dr. Edna Negrón

Advisory Committee

Composed of individuals from

• Auburn University
• Clemson University
• Colorado State University
• Cornell University
• Kansas State University
• North Carolina State University
• University of California-Davis
• Washington State University
• Alltrista Consumer Products Company
• National Presto Industries, Inc.

Objectives

• Collect and critically review literature relevant to home food preservation techniques and guidelines.


• Update the current guidelines, incorporating new or revised recommendations as appropriate.


• Develop and test new recipes (products) and guidelines on home food processing and preservation methods that emphasize: (a) popular consumer specialty foods; (b) safety guidelines for processing food in community cannery settings; and (c) applications of updated technology, such as microwave blanching for food freezing.


• Establish distribution mechanisms for dissemination of guidelines.


• Identify areas where further research in home food processing and preservation techniques is needed.

 

Product Development

• Mango salsas and chutney
• Mango relish
• Tomatillo relish
• Spicy jicama and watermelon rind relishes
• Pickled jicama
• Sweet pickles with Splenda®
• Jams/jellies with tropical fruits
• Hot pepper sauces
• Lemon curd/butter
• Sauces/marinades

Applied Research

• Microbial profiles of selected fresh herbs and whole spices used in home preparation of flavored vinegars, salsas, oils.
  • Supports the use of a chlorine wash to reduce loads prior to flavoring vinegars.


• Effect of pressure canner size on heat penetration in stewed tomatoes.
  • 6 and 8 qt cooker, 17 qt canner
  • 15 psig

Other Research Questions

• Documenting effect of fill weight on heat penetration.
  • Jicama relish/salsa
    • An increase of 118 grams solids per pint jar significantly increased the heat penetration rate (fh) and more than doubled the required processing time for this product.
    • A decrease of 5°C in the initial fill temperature did not change the heat penetration rate (fh) or processing time for this product.

Other Research Questions

• Alabama A&M University
  • Microwave blanching for freezing vegetables.
  • Accuracy and testing issues with dial gauges for canners.


• University of California-Davis
  • Survival and outgrowth of C. botulinum in garlic/oil products.

Why ??

Do people still can (preserve) food at home?

Surveys

• Survey of State and County Extension Faculty
  • Email in March 2000.
  • Responses from 225 Extension agents representing 24 states.
  • 45 percent of home food preservation requests are for canning, 21 percent for freezing and 12-13 percent for pickles and jams/ jellies.
  • Most requested processes are for condiments.
  • Issues regarding processing equipment and evaluating recipes were cited by more than 50 percent of respondents.

National Survey 2000

• To determine activity in home canning and freezing, and use of critical safety practices.


• 500 complete telephone interviews from households randomly selected across the U.S.
  • Individual telephone interviews
  • 38 questions on canning
  • 42 questions on freezing


• Conducted by Survey Research Center, University of Georgia.
  • October 24, 2000 and January 10, 2001

Current Canning Practices

• 135 (of 500) reported canning foods.


• Sources of instructions
  • friends or relatives (48%)
  • cookbooks (19%)
  • jar manufacturers (10%)
  • USDA or Extension Service (6%)


• 67% (90) of the respondents used their home canning instructions 'as is'
  • 29% (39) adapted them for use.

Current Canning Practices

Slide 26: Current Canning Practices

Current Canning Practices

Botulism from Home Canned and Processed Foods, 1970-80

Other Work in Process

Research

• Evaluating long-standing recipes for home cured meats/sausages; validating basic recipes.
• Developing original reduced fat sausages.
• Continued development of "specialty" foods - salsas, sugar concentrates, relishes, sauces and marinades.
• Looking at sugar substitution for sweet pickles and spreads.
• Equipment issues - canner size and steam canners.

Other Work in Process

Communications and Education

• Website: www.homefoodpreservation.com
• Emphasizing resources in the nationwide Cooperative Extension System and from USDA.
• Dissemination mechanism for NCHFP products.
  • Publishing literature reviews and technical bulletins of critical preservation points.
  • Research presentations and abstracts.
  • Factsheets - e.g., new products for home canning.
  • How to's for consumers.
  • Resources and historical information for educators.
  • Slides shows, graphics galleries, exhibit ideas.
  • Flash tutorials on the basics of home food preservation.
  • On-line course for self-study coming in 2004.

Other Work in Process

Communications and Education

• Publishing Complete Guide to Home Freezing in 2003; then updated Complete Guide to Home Canning in 2004.
• Master Food Preserver model curriculum for states to use.
• Educational video series.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Andress, E.L. 2003. National Center for Home Food Preservation. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

E. M. D'sa and E. L. Andress, Dept. of Foods & Nutrition, University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602-4356.

Paper 33C-10. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Abstract

Adequate thermal treatment in home-canned products ensures product safety from pathogens including Clostridium botulinum, eliminates the risk of spoilage microflora outgrowth and ensures product shelf-stability.

The objective was to experimentally calculate a thermal process recommendation for home canning of an acid salsa-type product and to determine the effect of consumer procedural variations on product heat penetration patterns.

An original standardized cranberry salsa (equilibrium pH 3.1) was filled into pint home canning jars. The cold spot was determined with thermocouples inserted through two-piece canning lids, to monitor temperatures at each of five potential cold spots in eighteen canner loads. Sealed jars were placed in a boiling water canner and temperatures recorded using Ellab™ software, through come-up, cool down, and a processing time that ensured that all jars reached a minimum of 2°C below processing temperature. Analyses of f(h) values (slope of the straight line portion of a heating curve) located the cold spot at the geometric center of the jar. Product cold-spot temperatures were then monitored through canning processes that produced a minimum temperature of 90.5°C, for standard filling procedures and variations of high-fill weight and low-initial temperature procedures.

A calculated 10 min boiling water process ensures adequate thermal treatment for this product. Up to a 10 minute post-cook lag prior to filling jars, and up to a 30g increase in product fill weight did not significantly change f(h) values, when compared with the standard treatments.

Home canning is a significant means of food preservation in some U.S. households, utilizing seasonal produce and in some cases contributing to food security. Confidence in thermal processing methodology recommendations is necessary for novel ethnic-type products. This paper presents data on thermal processing studies carried out on a conduction-heating food item and explains the effects of procedural variations inadvertently introduced during the canning process.

Introduction

The demand for novel home-canned products is constantly increasing, especially those using unusual food items, and those prepared and used in novel ways (Andress, 2001). The objective of this project was to develop a new salsa product using cranberries, and determine an adequate thermal process that would make the salsa not only highly palatable for independent use or in combination with other foods, but also safe when home-canned under recommended home-canning conditions.
The cranberry salsa is an acid food (pH < 4.6), and thus the primary concern was to ensure the development of a standardized product, prevent spoilage from acid-resistant microorganisms and produce an adequate jar vacuum seal.

Ingredients and Preparation Process

Spicy Cranberry Salsa:
Ingredients: 6 cups chopped red onion, 4 finely chopped large Serrano peppers*, 1½ cups water, 1½ cups cider vinegar (5%), 1 tablespoon canning salt, 1-1/3 cups sugar, 6 tablespoons clover honey, 12 cups (2¾ pounds) rinsed, fresh whole cranberries.
*Caution: Wear plastic or rubber gloves when handling and cutting hot peppers or wash hands thoroughly with soap and water before touching your face or eyes.

Yield: About 6 pint jars.

Procedure:

Thermal Process Development

Determination of the cold spot for this product and jar combination was made using data collected for heat penetration curves at 5 potential cold spot locations in the jars in 18 canner loads (see Table 1).
Two levels of two procedural variations were used in testing for process calculations. Temperature profiles were compared for two fill weights (450g, 480g) and two fill temperatures (direct-fill, and after a 10 minute wait, which had means of 84.4° and 80.4°C, respectively. Process calculation was accomplished by using thermocouples in each of six jars in different canner loads of each of the three fill methods (standard, low initial temperature, and high-fill weight). These jars were processed to 90.5°C plus an additional 5 minutes.
Processing was done in a boiling water canner using the stovetop burners of a household gas range (Frigidaire Gallery Model ES III. Data were recorded using an Ellab E-Val™ Monitoring System and software and Ecklund needle Type T copper-constantan thermocouples. Analysis of variance was used to determine if significant (p<.001) differences existed between the treatments using the General Linear Model procedure in SAS 8e (1999-2001).

Results

Cold Spot Location

• The cold spot for this product and jar combination was located at the geometric center of the jar (Table 1).
• The f(h) value is the number of minutes it takes the straight line portion of the heat penetration plot to pass through one logarithmic cycle.
• A larger f(h) represents a slower rate of heat penetration.

Thermal Characteristics of Jars Processed by Three Procedures

• The initial canner temperature was consistently maintained at 82.0-82.5°C prior to the loading of filled jars (Table 2).
• The initial temperature for this product as prepared and filled into jars by usual home canning practices ranged from 77.81-90.19°C in the standard series.
• There was greater variability among initial temperatures in the series used for HFW (overfill) and LIT (low initial temperature) calculations, but this difference did not effect the interpretation of findings or the ultimate process recommendation.

Determination of the Calculated Thermal Process

• Pflug(1998) outlines guidelines for thermal process calculations, based on the equilibrium pH of the product. This is then correlated to a  in minutes, based on product pH. Since the equilibrium pH of the cranberry salsa product is 3.1, according to process development guidelines a minimum  of 0.1 minutes is enough to ensure an appropriately canned product.
• The  of 0.1 minutes for the cranberry salsa is achieved within the come-up time of the product, itself.
• Thus, a 10 minute process time was determined for the product, this time would be sufficient to achieve the desired lethality, as well as ensure a proper vacuum seal for the jar lid and sterilization of the glass jar (Table 3).

Effect of Fill Weight and Initial Jar Temperature

• An increased fill weight (up to 30g over the standard pint jar fill weight) had no significant effect on the f(h) values and thus thermal process, for the cranberry salsa product in pint jars.
• A 10 minute pre-fill cooling time (which resulted in a mean 4°C temperature difference) had no significant effect on f(h) values and thus the thermal process, for the cranberry salsa product in pint jars.
• Both procedural variations of increased fill weight and lowered initial jar temperature had no significant effect on the final product temperature at the end of the process.
• A 4°C decrease in fill temperature did not significantly change the number of minutes at boiling for the cold spot to reach 90.5°C (Table 4).

Summary and Conclusions

• An increase of 30 grams product per pint jar did not significantly increase the heat penetration rate (fh).
• A decrease of 4°C in the initial fill temperature did not change the heat penetration rate (fh) or processing time for this product.
• Canning instructions should be specific for the product composition, jar dimensions, and number of jars per recipe.

References

	1.	Andress, E.L. 2001. A national survey of current home canning practices in the U.S. Athens, GA: National Center for Home Food Preservation, Department of Foods and Nutrition, The University of Georgia. Unpublished data.
	2.	Garner, H. H. and Andress, E.L. 2002. Effect of fill weight and initial temperature on processing time for a home pickled jicama relish. Poster presented at IFT Annual Meeting, Anaheim, CA.
	3.	Pflug, I. J. 1998. Microbial Control Processes  for Acid Foods. In Microbiology and Engineering Processes. Environmental Sterilization Laboratory, Minneapolis, MN
	4.	Statistical Analysis Software, v. 8e. 1999-2001. Cary, NC: SAS Institute Inc.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. E. M. D'sa and E. L. Andress. 2004. Thermal Process Development of a Home-Canned Salsa-Type Product. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

B. A. Nummer, M. Thacker, E. M. D'Sa, and E. L. Andress, Dept. of Foods & Nutrition, University of Georgia, 328 Hoke Smith Annex, Athens, GA 30602-4356.

Paper 33C-9. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Abstract

Salsa is America's No. 1 condiment. This popularity has extended to home food preservers who want to make use of a seasonal harvest of garden-grown tomatoes and vegetables. Most salsa recipes mix low-acid foods, such as onions, green peppers, and jalapeño peppers, with acid foods, such as tomatoes. Currently the USDA and the National Center for Home Food Preservation recommends that a boiling water canning process be used only for research-tested salsa recipes that provide evidence of safe acidification to inhibit Clostridium botulinum growth. Only a few such research-tested salsa recipes are available and these must be followed with little deviation.

This project sought to create and test a guideline recipe for salsa that allowed for variations in low-acid ingredients, while maintaining a safe level of acidification from tomatoes and lemon juice.

Based on this research a safe recipe guideline ratio of 200 g Roma tomatoes, 200 g (onions, peppers, and dry spices), and ¼ cup (60 ml or 61g) of bottled lemon juice per pint volume was proposed. The lemon juice (60 ml) safely acidified a lab recipe (200 g Roma tomatoes, 120 g onions, 65 g green peppers, 15 g jalapeño peppers, and 5 g table salt per pint) to below pH 3.82. Salsa made from 200 g tomatoes, ¼ cup lemon juice and either all onions (200 g) or all green peppers (200 g) as the low-acid ingredient maintained a pH below 3.82. In acidification curves single low-acid salsa ingredients needed only 10 ml lemon juice per 200 g vegetable to acidify below pH 4.6. Furthermore, 60 ml lemon juice per pint safely acidified full pint volumes (263-304 g) of onions, green peppers, or jalapeños alone to below pH 3.82. Informal taste panels indicated an acceptable salsa flavor after canning using recipes within the guideline.

Introduction

Most tomato-based salsa recipes mix low-acid foods, such as onions, sweet and/or hot peppers, with acid foods, such as tomatoes. Currently the USDA (2) and the National Center for Home Food Preservation (http://www.homefoodpreservation.com) recommend that a boiling water canning process be used only for research-tested salsa recipes that provide evidence of safe acidification to inhibit Clostridium botulinum growth. The USDA Complete Guide to Home Canning (2) has only one salsa recipe. Research by Hillers and Dougherty (1) created six more salsa recipes for home canning and these have been attached to the USDA Complete Guide to Home Canning by Utah State University as an addendum to Guide 3. Hillers and Dougherty note the only safe changes a home food preserver can make to their listed recipes is to substitute bottled lemon or lime juice for vinegar or to change the amount of spices and herbs. This project sought to create and test a guideline recipe for salsa that allowed for minor variations in low-acid ingredients, while maintaining a safe level of acidification from tomatoes and lemon juice.

Materials and Methods

Figure 1. Guideline Salsa Recipe ~ per pint jar

• ¼ cup lemon juice (60 ml)
• 200 g Roma tomatoes (peeled, deseeded, and diced to approx. ¼") ~ tomato juices were drained and discarded
• 200 g any combination of onions, bell peppers (diced to approx. ¼") and pureed hot peppers including seeds
• ¼ tsp salt

Processing: All of the ingredients were combined in a saucepan and brought to boil over medium heat with stirring. The heat was reduced and the salsa was simmered for three minutes. Salsa was packed into clean, hot, pint-size canning jars leaving a ½ inch headspace.

Boiling water processing: Jar rims were wiped and standard metal two-piece lids were added; then the salsa was processed for 15 minutes in a boiling water canner using the standard consumer methods referenced in the USDA Complete Guide to Home Canning (2).

Ingredients

All foods were obtained from a national grocery chain. Vegetables were of high quality (no bruising, firm and disease free) and were kept refrigerated until use. Acidifying agents were ReaLemon® juice or ReaLime® juice, and Kroger® brand 5% acetic acid vinegar.

Tomatoes were dipped in boiling water for 1-2 minutes until the skins wrinkled, then submerged into cold water. Loose skins were peeled off. Tomato flesh was cored, cut into pieces, and deseeded. The pieces were then cut into approximately ¼ inch cubes and the juices drained off through a colander. Onions and peppers were cut into approximately ¼ cubes. De-stemmed jalapeño peppers were puréed including seeds to maintain the capsaicin.

Acidification of a tomato, onion, and pepper salsa

Diced salsa ingredients (200 g Roma tomatoes, 120 g sweet onions, and 65 g sweet peppers), 15 g puréed jalapeño pepper, and 5 g salt were cooked with (¼ - 3/8 cup) vinegar, lemon juice or lime juice and canned in pint jars. The mixture was cooked, packed into hot pint jars, capped, and processed for 15 minutes (Figure 1.). After 24 h the product pH was determined from blended solids and brine. The goal was to obtain a quality product with a pH below 4.0 and closer to pH 3.8.

Acidification of individual ingredients by lemon juice

Lemon juice (0, 5, 10, 15, 20, 25, and 30 ml) was added to 100 g (¼" cubed) sweet green peppers, Roma tomatoes, white onions and hot (jalapeño) peppers. Each vegetable was placed into a half pint canning jar with the measured amount of lemon juice, and tap water to reach a ½" headspace. Three jars of each treatment were measured. Jar contents were cooked, repacked into hot jars, capped, and processed for 15 minutes (Figure 1.). After cooling overnight pH measurements were taken.

Measurement of pH

An Orion 520 A+ pH meter was used for all measurements. Readings were an average of three measurements made in different locations of the sample. A brine pH was determined by inserting the probe directly into the jar and reading the pH. A solids pH was determined for both un-rinsed solids and rinsed solids. The solids were drained in a U.S. standard No. 8 sieve inclined at a 17-20 degree angle for two minutes. For rinsed solids, 15 ml tap water was sprayed over the solids on the sieve and allowed to drain. Un-rinsed or rinsed solids were blended and the pH measurement was taken.

Acidification of pepper and onion varieties by lemon juice

Three varieties of sweet bell peppers (yellow, green and red) and three varieties of onions (yellow, white and purple) were cut into ¼ inch sized cubes and 200 grams of each were added to pint mason jars. Lemon juice (¼ cup) was added. Tap water, if needed, was used to top jars to a ½ inch headspace. Jar contents were cooked, repacked into hot jars, capped, and processed for 15 minutes (Figure 1.). After cooling overnight pH measurements were taken.

Acidification of excess quantities of low acid vegetable by lemon juice

Three varieties of sweet bell peppers (yellow, green and red) and three varieties of onions (yellow, white and purple) were cut into ¼ inch sized cubes. The maximum volume of vegetable was pressed into pint mason jars allowing for a ½" headspace; fill weights were recorded. Lemon juice (¼ cup) was added. Tap water, if needed, was used to top jars to a ½ inch headspace. The jar contents were cooked, packed into hot jars, capped, and processed in a boiling water canner for 15 minutes (Figure 1.). After cooling overnight pH measurements were taken.

Results

Acidification of a tomato, onion, and pepper salsa
 

• Lemon and lime juice (¼ cup per pint) provided the best acidification of the salsa to pH 3.8 – 4.0. Lemon juice had a milder flavor, while lime juice provided a lime flavor that would be appropriate to this type of salsa. Lemon juice was chosen to continue experiments.

Acidification of tomatoes, peppers, and onions by lemon juice

Lemon juice acidification curves were created for sweet green peppers, Roma tomatoes, white onions and hot (jalapeño) peppers (Figures 1A-D.).

• Lemon juice (15 ml) safely acidified 100 g of each vegetable to below pH 4.0. Brine and solids pH measurements were nearly identical indicating acid equilibration within the 24 h period. When 30 ml of lemon juice was added to 100 g of vegetable the pH was safely reduced for: sweet green peppers (pH <3.43), Roma tomatoes (pH <3.38), white onions (pH <3.44) and hot (jalapeño) peppers (pH <3.73).
• It was interesting to note that this skinned and deseeded Roma tomato flesh had a pH of 4.6-4.7. This was most likely due to loss of acid in the tomato juice that was intentionally not used to avoid a watery salsa.
• The data suggest that 30 ml bottled lemon juice will safely acidify 100 g of tomatoes, peppers, or onions; or some combination of these ingredients.

Acidification of full pint volumes of onions, green peppers and jalapeño peppers

Full pint volumes of low acid vegetables (onions or peppers) were combined with ¼ cup of lemon juice (60 ml) to determine if consumer error could lead to unsafe acid levels in the guideline salsa recipe. Several varieties of onions were packed tight into a pint jar and weighed. From 263 – 295 g fit into jars from nine replicates. The maximum pint volume of green peppers weighed from 296 – 304 g for three replicates. After adding lemon juice, cooking, and boiling water processing, the full pint volumes of acidified onions had a pH range from 3.59 – 3.82 and full pint volumes of acidified green peppers had a pH range of 3.66 – 3.80 (data not shown).

Acidification of tomatoes, peppers, and onions by lemon juice and Roma tomato

The experimental salsa recipe allows consumers to vary the quantity of low acid ingredients (onions and peppers) from 0-200 g per pint of salsa. Thus the acidification of single low acid vegetables by 200 g Roma tomato and ¼ cup lemon juice was examined
 

Table 2. pH of salsa made with 200 g Roma tomato,
¼ cup lemon juice and 200 g of single low acid vegetables

Discussion

• Lemon juice (¼ cup or 60 ml) safely acidified a guideline salsa recipe containing 200 g Roma tomatoes, 120 g onions, 65 g peppers, 15 g hot pepper purée, and ½ tsp salt to a pH below 4.0. The flavor and color of this salsa after canning was of acceptable quality based on preliminary tests.
• Lime juice provided the same acidification of the salsa, but it had a much stronger lime flavor and aroma.
• A larger volume of vinegar was needed to achieve equivalent pH values for the salsa mixture; this volume resulted in a pronounced flavor change.
• Acidification curves indicated that lemon juice (30 ml per 100 g vegetable) could safely acidify tomatoes, peppers, or onions prepared under the conditions in this experiment.
• Salsa made from 200 g Roma tomatoes, ¼ cup bottled lemon juice and either all onions (200 g) or all green bell peppers (200 g) was safely acidified.
• Using the correct amount of bottled lemon juice (¼ cup per pint) full pint volumes of either onions or bell peppers are safely acidified. This helps provide a safer recipe despite the possibility of consumer error.
• This recipe is not yet being recommended for public use until there is further research and peer review. Validation with more replications and in larger batch recipes and heat penetration studies are needed. The final goal is a recipe that could be validated to allow consumers some measure of creativity in mixing their low-acid ingredients in a tomato-based salsa to maintain safe acidification for boiling water canning.

References

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. B. A. Nummer, M. Thacker, E. M. D'Sa, and E. L. Andress. 2004. Studies on safe acidification of salsa for home boiling water canning. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

W.L. Kerr*, S.G. Choi and E.L. Andress**

* Dept. of Food Science and Technology, University of Georgia, Athens,GA 30602
** Dept. of Foods and Nutrition, University of Georgia, Athens, GA 30602

Paper 33C-7. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Abstract

Reduced fat Italian sausage was prepared with oatmeal at 10, 20, and 30% (w/w), and oatmeal precook times of 0, 2, and 4 minutes. Cook loss and expressible moisture, cutting force and texture profile analysis, color, and consumer sensory analysis were analyzed by response surface methodology. Minimum cook loss occurred at 16.3% oatmeal and 0.76 min precook time, while expressible moisture decreased with increasing oatmeal levels and decreasing precook time. In general, both cutting force and hardness decreased with oatmeal level. Measurements of L*, a*, and b* showed a slightly lighter product, and a shift to more red and yellow cooked product at intermediate oatmeal levels and precook times. For sensory attributes, both oatmeal level and precook time were significant. Greatest flavor and texture likeability were attained with oatmeal levels of 3-12%, and precook times of 1.5-3 minutes. Greatest overall likeability occurred over a region of 0-14% oatmeal, and 1.1-3.3 minutes.

Objectives

Materials and Methods

• SAUSAGE PREPARATION
  • Visible fat removed pork loin was ground and mixed with oatmeal and additional seasoning. After mixing, the batter was stuffed into a collagen casing.
  • Oatmeal levels were 0, 10, 20, and 30%
  • Pre-cooking times were 0, 2, and 4 minutes

• Cooking loss and Expressible Moisture
  • % Cooking loss = [(Mb – Ma)/Mb×100%] (Mb & Ma : Weight before and after cooking sample)
  • % Expressible Moisture = [(Wb – Wa)/wb×100%] (Wb & Wa : Weight before and after compressing sample)

• Texture Analysis
  • Cutting force was measured with the Warner-Bratzler shear blade of the TA-XT2i, cut at 4.0mm/s
  • Texture profile (TPA): 1.5cm thick and 1.6cm diameter samples were compressed twice at 2.0mm/s to 50% of their original height.- Hardness, compression, adhesiveness (g.s) were determined.

• Color
  • For each batch, L, a, and b were determined using a Minolta chromameter before and after cooking

• Sensory Evaluation
  • Flavor, texture, color, and overall acceptability of the sausages were evaluated

• Statistical Analysis
  • Treatment differences were analyzed using analysis of variance (ANOVA)

Results

Table 1: Salsa pH vs. ANOVA and response surface statistics for sausage properties as a function of oatmeal level and precook time

Response	Range	Oatmeal p value	Precook Time p value	Oatmeal* Precook p value	Lack of Fit p > F	R²	Optimal Points (oatmeal/precook time)
%Cooking Loss	1.2 - 1 3.3	0.031	0.005	0.0038	<0.0001	0.89	2.07% (16.3/0.7) min
%Expr Moisture	2.0 - 7.7	<0.0001	<0.0001	0.075	0.0044	0.93	NA
Cutting Force (g)	790 - 1999	<0.0001	0.39	0.013	0.030	0.86	NA
Hardness (g)	1109 - 4968	<0.0001	0.073	<0.0001	0.17	0.96	NA
Adhesiveness (g s)		0.024	0.22	0.55	0.32	0.41	889 gs (12.9/1.4) max
Cohesiveness		<0.0001	0.004	0.25	0.012	0.83	0.39 (31.7/2.4) sp
L*	42.5 - 50.2	0.047	0.20	0.36	0.15	0.52	45.7 (14.7/2.4) sp
a*	3.86 - 5.28	0.67	0.19	0.14	0.0098	0.68	4.86 (14.7/2.43) max
b*	8.6 - 15.8	0.021	0.41	0.27	0.089	0.62	12.5 (8.93/2.22) sp
Sensory Flavor	4.74 - 6.78	<0.0001	0.0076	<0.0001		~1	7.03 (3.26/3.17) max
Sensory Texture	4.37 - 7.02	<0.0001	0.12	0.0077		~1	6.89 (6.04/2.26) max
Sensory Color	5.3 - 6.02	0.86	0.0009	0.0013		~1	NA
Overall Likeability	4.51 - 6.79	<0.0001	0.0044	<0.0001		~1	6.96 (8.05/2.27) max
NA=optimum out of data range, min=minimum, max=maximum, sp=saddle point

Cooking loss and Expressible water

Figure 1. Cooking loss

• Minimum cook loss(2.1%) was were 16.3% and 0.76min precook time
• Higher levels of oatmeal and increased precook time produced more cook loss

Figure 2. Expressible moisture

• Range was 2 to 7%
• The response surface showed gradually decreasing values at higher level of oatmeal & shorter precook time

Texture Analysis

Figure 3. Cutting force

• Cutting force decreased with oatmeal level
• Oatmeal level was the greatest contribution to decreasing force

Sensory Evaluation

Figure 4. Flavor

• A maximum value (7.03) was predicted at 3.3% oatmeal level & 3.2 min precook

Figure 5. Texture

• Maximum texture likeability (6.8) was predicted at 6.04% oatmeal and 2.3min precook time

Figure 6. Overall likeability

• Maximum likeability was predicted at 8.05% oatmeal % 2.27 precook time

Conclusion

• A likeable pork sausage can be made in which fat is replaced with up to 15% oatmeal.
• Such products contain improved flavor and texture as compared to low-fat controls.
• Higher levels of oatmeal resulted in a product with more cook loss, softer texture, less cohesion, and minor changes in color.
• Precooking time of the oatmeal is important, particularly to cook loss, cohesiveness, and flavor.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. W.L. Kerr, S.G. Choi and E.L. Andress. 2004. Physical and Sensory Characteristics of Reduced Fat Italian Sausage Prepared with Oatmeal. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

Jin Kyung Kim*, Elaine M. D'Sa**, Mark A. Harrison*, Judy A. Harrison**, and Elizabeth L. Andress**

* Dept. of Food Science and Technology, University of Georgia, Athens
** Dept. of Foods and Nutrition, University of Georgia, Athens

Paper 33C-1. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Note: This research study analyzed one particular pickling procedure that started with partially fermenting cucumbers at room temperature and then storing them in the refrigerator with no further treatment or processing. It does not represent findings or advice for any other type of refrigerator pickles.

Abstract

Listeria monocytogenes can survive and grow in refrigerated foods with pH levels of approx. 4.0-5.0 and salt concentrations of 3-4%. Home-fermented refrigerator dill pickles fit this description. Contamination of this product with L. monocytogenes could cause serious problems since these items are not heated prior to consumption. This study determined L. monocytogenes survival and growth patterns in refrigerator dill pickles at three salt levels. Pickling cucumbers were inoculated with L. monocytogenes, brine mixtures were added and the cucumbers were held at room temperature for one week and then refrigerated for up to 3 months. The pH, percent NaCl, percent titratable acidity and total aerobic, psychrotrophic, lactic acid bacteria and Listeria populations were measured at the addition of brine, at 2, 4, and 7 days during storage at room temperature and then at weekly intervals during refrigerated storage. There was a rapid decrease in pickle pH after four days at room temperature (from 6.1-6.2 to 4.4-4.6) followed by a gradual decrease. The percent NaCl in the pickles rapidly increased up to 3 weeks at refrigeration temperatures, and the percent titratable acidity in the highest salt level was significantly lower (p<0.05). The initial Listeria population was 5.4-5.6 log cfu/cm² on the surface and 3.9-4.6 log cfu/g internally. There was approximately a 0.5-1 log increase during fermentation at room temperature followed by a population decline during refrigerator storage, with a greater decrease in the pickles with the highest NaCl content. Populations of total aerobes and lactic acid bacteria increased during room temperature storage and decreased gradually.

Introduction

• L. monocytogenes has been a major food safety concern since the 1st outbreak due to consumption of coleslaw in 1981 (Shlech 1983)
  • L. monocytogenes is widely distributed in the environment
  • Isolated from various environment and food sources
  • Cross-contamination with L. monocytogenes can occur
  • Found within the food manufacturing environment
  • Can attach to various manufacturing surfaces and produce a biofilm
• Adaptation of L. monocytogenes to environmental stresses
  • pH: can survive and/or grow as low as pH 4.4 (George 1988)
  • Salt concentration: can survive up to 14% NaCl (Farber 1992)
  • Temperature: remain metabolically active at 3°C (Walker 1990)
• Pickling (Brandt 1996)
  • Preserving vegetables, meat and fish with salt and acid
  • Cucumbers are one of the more commonly pickled foods in the U.S.
• Home-fermented refrigerator dill pickles
  • Lactic acid fermentation of cucumbers
  • Made by immersing the pickling cucumbers into a brine solution
  • Kept at room temperature for 1 week followed by storage at refrigeration temperatures during the consumption period

Objective

To determine the fate of L. monocytogenes on the surface and in the interior of cucumbers and in brines subjected to the different salt levels (1.3, 3.8, 7.6%)

Materials and Methods

• Bacterial strains and inoculum preparation
  • Five L. monocytogenes strains, 301, V7, LCDC, Scott A, and Brie used
  • Cultured in 10 ml of TSB and incubated for 24 h at 37°C
  • Transferred to 4,000 ml of TSB and incubated for 24 h at 37°C
  • Centrifuged at 4,550 x g for 30 min
  • Pellet was resuspended into sterile 0.1% peptone water

• Inoculation of cucumbers
  • Long, unwashed, pickling cucumbers (approx. 10 cm)
  • Washed with tap water and drained for 30 min
  • Immersed cucumbers into an inoculum of L. monocytogenes for 15 min
  • Cucumbers drained on a sterile metal grid rack for 15 min
  • 3 salt levels (1.3, 3.8, and 7.6%) with L. monocytogenes and a control treatment of 3.8% NaCl and no inoculum used

• Physical Analyses
  • pH measurement in cucumbers and brines with a pH meter
  • Percent titratable acidity: titrated 20 g of sample with 0.1N NaOH - % Acid = (mL NaOH)(N NaOH)(milieq. wt of acid)(100)(wt of sample(g))-1
  • Percent NaCl: Quantab chloride titration strips with calibration table

• Microbiological properties
  • Sampling interval: at the addition of brine (0), 2, 4, 7 d at room temperature, 1, 2, 3, 4, 6, 8, 10, 12 weeks during refrigerated storage
  • Sampling procedure
    • Surface of cucumber: cut into 2.5 x 2.5 cm pieces using sterile knife
    • Interior of cucumber:10 g, using sterile corer from the blossom end
    • Brine: directly diluted using peptone water
  • Microbiological count
    • Total aeobes: PCA, incubated at 35°C for 24 h
    • Psychrotrophs : PCA, incubated at 7°C for 7 d
    • Lactic acid bacteria: MRS 2X, incubated at 35°C for 48 h anaerobically
    • Listeria: LSA (Listeria Selective Agar), incubated at 35°C for 48 h
  • Listeria enrichment
    • 1 ml of from bag inoculated into 9 ml LEB (Listeria Enrichment Broth)
    • Incubated at 30°C for 48 h
    • Streaked onto LSA and incubated at 35°C for 48 h
    • Checked for Listeria colonies
  • Identification and confirmation test
    • Gram stain, Catalase/Oxidase reaction
    • Umbrella-like growth in motility medium
    • Biochemical testing using Micro ID kits (Remel, Lenex, KS)

• Statistical Analysis
  • ANOVA (Statistical Analysis Systems Institute, Cary, NC)
  • Duncan's multiple range tests - significance value: =0.05

Results

Table 1. Population of L. monocytogenes on surface and in interior of cucumbers at three salt levels 

1/3    Number of tubes showing positive result /number of replicates

• Initial population - Surface: 5.4–5.6 log cfu/cm²; Interior: 3.9–4.6 log cfu/g
• Listeria populations decreased the most in the highest salt content during refrigerator storage
• Listeria populations were not detected on surfaces or in the interiors, after 8 and 4 weeks at refrigerator temperature, respectively

Fig. 1. Change patterns of microorganisms in the brines at three salt levels
A)Listeria    B) Total Aerobes    C) Lactic Acid Bacteria    D) Psychrotrophs

• Similar change patterns were observed for each type of microorganism
• Initial population of L. monocytogenes: 6–6.1 log cfu/ml
• Total aerobes increased by 3 logs after 4 d at room temperature and then, gradually decreased
• No significant difference (p>0.05) in the number of lactic acid bacteria among salt levels

Table 2. Population of total aerobes on surface and in interior of cucumbers at three salt levels 

• Aerobic populations were significantly higher (p<0.05) at 1.3 % salt levels
• Aerobic populations were greatest at 4 (surface) or 7 (interior) d at room temperature
• Aerobic populations decreased gradually during refrigeration temperature

Fig. 2. The pH and percent titratable acidity at three salt levels - A) Cucumbers B) Brines

• There was a rapid pH decrease from 6.1–6.2 to 4.4–4.6 (cucumbers), from 5.5 to 3.6–3.9 (brines), except the highest salt level (from 6.2 to 5.2), by the 4th day.
• Significantly lower (p<0.05) percent titratable acidity for brines in 7.6% salt level

Table 3. Population of psychrotrophs on surface and in interior of cucumbers at three salt levels 

• Psychrotrophic populations increased 1-2 logs at room temperature and then decreased
• Psychrotrophic populations decreased 2-3.5 logs at the end of storage time
• For each sampling day there was no significant difference (p<0.05) in psychrotrophic populations in the pickle interiors among salt levels

Conclusion

• Based on old recommendations, consumption of refrigerator dill pickles could typically occur anytime after 3 days of refrigerated storage
• Since L. monocytogenes may still be viable well after this point, there is a food safety risk involved
• Recommendations to prepare this product in the home should not be distributed

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. Jin Kyung Kim, Elaine M. D'Sa, Mark A. Harrison, Judy A. Harrison and Elizabeth L. Andress. 2004. Listeria monocytogenes survival in refrigerator dill pickles. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

P. Wambura¹, J.C Anderson and L.T. Walker¹

¹Dept. of Food & Animal Sciences, Alabama A&M Univ. P.O Box 1628, Normal, AL 35762-1628
²This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Paper 17H-19. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Abstract

Effects of entrapped air during thermal processing on lethal effect were evaluated in three domestic canners with seven (7) quart mason jars. Entrapped air volumes in ceramic-bead products were established with various fillings of water into dry product matrix. Alternate periods of venting included none, 5, 10, and 15 min. Lethal effects were determined using thermocouples positioned near the bottom, middle, and top of model product and others outside the jars. Process pressure was monitored throughout each of the 72 runs.

Two canners (All American and Mirro models) were continuously vented during processes while the third (National Presto) was not - but was vented de facto until lid lock moved up under influence of escaping gases. Nevertheless, venting times and lack of continuous venting demonstrated little impact. The higher lethal effects were noted when least product-entrapped air was modeled. Differences were noted between pressure processes monitored by dial gauge versus calibrated weighted-devices with more variation of the dial gauge system and greater lethal effect due to manual control basis. Besides lethal effect differences with product-entrapped air, the three positions of thermocouples registered least thermal effect at top portions of the jars. All manufacturers of domestic canning kettles emphasize periods of venting to eliminate air in the canners prior to the timed processing but this study only reflected suppressed lethal effects when containers manifested product-entrapped air.

Introduction

Consumption of under-processed food constitutes a significant risk of food-borne illness. It is estimated that food-borne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year (Mead et al., 1999).

Air is a poor heat transfer fluid since it has low specific heat and thermal conductivity. Recommendations have been published seeking to ensure adequate venting of air from the pressure canner in manners similar to commercial practices where particularly for flexible pouches in stacks the call is to remove air from container external contact surfaces (Ramaswamy and Grabowski, 1996).

Several studies that have been carried out on evaluating the effect of air entrapped in flexible packages (retortable pouches) reported that air leads to decrease in the heating rate, reduction in heat transfer rate, and reduction in the accumulated lethality (Weintraub et al., 1989; Campbell and Ramaswamy, 1992; Ramaswamy and Grabowski, 1996; Brennan et al., 1976).

The main objectives of this study were to contrast canner types and to evaluate temperature distributions within model product with variation of three levels of product-entrapped air (three water-fill levels) within the three pressure canners during cooking cycles preceded by three venting schedules.

Materials and Methods

• Temperature distribution profiles on the central axes of one-quart mason jars (946 ml) filled with ceramic beads and three (3) water level fills were conducted with three domestic pressure canners (an All American model 921, a Mirro model 0522, and a National Presto model 01780).
• Temperature distribution during venting was measured by copper-constantan thermocouples placed in specific location in each.
• Seven (7) Ecklund Harrison thermocouples were placed into the seven (7) mason jars to monitor temperature profile development inside the jars.
• The twelve (12) bare thermocouples and 5 more Ecklund-Harrison models were placed in specific locations around the inside of the cooker to monitor temperature development inside the pressure cooker.
• Three levels of product-entrapped air were conducted with each of the All American, Mirro and National Presto pressure canners.
• Jars (946ml) were filled with a 910g of dried ceramic beads.
• Jars were filled in turn with water to one of the three levels (120, 240 and 360g) at room temperature and closed with lids and rings before being loaded into the cookers. Rings were not severely tightened so as to allow air to escape.
• Experiments were conducted in random orders with venting times of 5, 10, and 15 min. Another series of experiments were done with no venting throughout.
• Thermocouple output were recorded through the Omega TempScan 1000 data logger.
• Reference lethal effects were determined by monitoring pressure development with a transducer and calculating lethal effect with conversion of pressure units to temperature by the Clausius-Clapeyron equation.
• Thermocouple and pressure transducer outputs were recorded through the Omega TempScan 1000 data logger. Displaying and recording of the data logger temperatures and pressures were facilitated with a personal computer and the Omega TempWin software.
• The beginning of venting time was noted when a constant stream of gases were indicated flowing rapidly out of the vent tube and continued until the vent tube was capped off.
• Start of processing was taken as the time when the cooker was brought up to pressure indicated when the calibrated-weight gauges would jiggle at approximately 70 kPa or when the Presto dial gauge reached the approximate 70 kPa mark (indicated as 10 psi). 31-minute processes were followed by slow cooling with the heat turned off.
• Lethalities (F-values) were calculated using the General Method (T = 121.1°C). Kinetic parameter for C. botulinum spore inactivation (Z = 10C°) was selected. Relative lethal effects were noted as percentage of the pressure-based lethal effects.
   

  

Statistics

Three-by-three design space factors (venting times and water fill levels) were regressed with the RSREG procedure employing co-variables of unary types for the three canners and the thermocouple positions using the SAS® for Windows software (Copyright (c) 1999-2001 by SAS Institute Inc., Cary, NC).

Results and Discussion

Table 1: Lethal Effects in Minutes based upon Direct Thermocouple Temperature Data


Table 2: Percentages of Lethal Effect of Points inside the Jars based upon Temperature Data Relative to Pressure Data

Notes: **** indicates significance p<0.0001; *** indicates significance p<0.005; ** indicates significance p>0.01; * indicates significance p<0.05; N.S. indicates not significant
 

Table 3: Percentages of Lethal Effect of Points outside of Containers based upon Temperature Data Relative to Pressure Data


Table 4: Percentages of Lethal Effect of Points inside Containers based upon Temperature Data Relative to Pressure Data Contrasting Categories of Venting Time

 

Notes: **** indicates significance p<0.0001; *** indicates significance p<0.005; ** indicates significance p<0.01; * indicates significance p<0.05; N.S. indicates not significant

Pressure Cookers Used

Transducer
 Left to right: All American, National Presto, Mirro

Experimental Setup

Discussion

• Direct thermocouple data transformations to lethal effect analyzed by the RSREG procedure displayed no design factor significances apart from the unary data of canner model and positions in the jars (Table 1).
• However, results from this data displayed non-significant differentiation based on the three pressure canners (as desired) only when the data values were made relative to pressure data (Table 2).
• When the data were considered relative to pressure, a linear dependence upon water level suggested improved lethal effects whenever the air-entrapped challenge for process was reduced. -- Prediction by this regression is an ~ 23% [2 X ~ 11.5 coded term] increase of lethal effect from the most air-entrapped model product to the least air-entrapped model product.
• Positions in the jars were basis for differing lethal effects with the top position experiencing the least while the bottom indicated as 5% (3% for total process) and the middle position indicated as 6% (7% for total process) greater than the top position (Table 2).
• When only the points monitored outside the jars were considered, no significant departure of lethal effect compared to the "Girdle" sites strapped to the jars was evident for the points suspended in spaces "Between" the jars (Table 3).
• The points in the lid dome area whether by the vent or away were much less exhibiting of lethal effect (Table 3).
• Differences were noted for the continuously vented systems of ~ 22 – 24% less at the vent area and ~ 15 – 16% less in the space away from the vent and appeared to represent a reduced transfer of heat in areas away from boiling water within which the jars were heated (Table 3).
• Greater depression of thermal effect for points by the vent may reflect a presence of air (that reduced the water vapor pressure and its associated temperature equivalent).
• Evidences by the coded water term of the greater mass of water enabling greater heat capacity to retain temperature in the vicinity of the jars by the "Girdle" positions were seen in the regression (Table 3).
• By three categorical terms of "not vented", "vented 5 minutes", and "vented more than 5 min." the indication came through that not vented at all was significantly less in lethal effect than 5 or more minutes (~4% less for the full process) (Table 4).
• For the shorter (31 min.) timed portion of the process by categorical groups the longer vent times were also ~3% more effective than the 5 min. vent time (Table 4).

Conclusion

• Manufacturers of domestic canning kettles emphasize periods of venting (7 to 10 min.) to eliminate air in the canners prior to the timed processing.
• Five minutes venting was a good as 10 min. in this study.
• Published recommendations appeared to give adequate margins of safety.
• Nevertheless, this synthetic product model did not represent the full range of potential foods that could be considered to qualify the recommendation.

Selected References

• Brennan, J.G., Butlers, J.R., Cowell, N.D., and Lilly, A.E.V. 1976. Food Engineering Operations, Second edition, Applied Science Publisher Limited, London.
• Campbell, S. and Ramaswamy, H.S. 1992. Heating Rate, Lethality and Cold Spot Location in Air-Entrapped Retort Pouches During Over-Pressure Processing. Journal of Food Science, 57: 485-489.
• Mead, P.S., Slutsker, L., Dietz, V., McCaig, L.F., Bresee, J.S., Shapiro, C., Griffin, P.M and Tauxe, R.V. 1999. Food-Related Illness and Death in the United States. Journal of Emerging Infectious Diseases, 5 (10): 607-625
• Ramaswamy, H.S. and Grabowski, S. 1996. Influence of Entrapped Air on the Heating Behavior of a Model Food Packaged in Semi-Rigid Plastic Containers during Thermal Processing. Journal of Food Technology. 29: 88-93. Academic Press Limited.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and Alabama A&M University receive acknowledgment and this notice is included:

Reprinted with permission of Alabama A&M University. P. Wambura, J.C Anderson and L.T. Walker. 2004. Influence of Product-entrapped Air and Venting on Lethal Effect in Model Domestic Pressure Canner Studies. Normal, AL: Alabama A&M University, Food and Animal Sciences Department.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

J. ROBERTS, L. T. Walker and J.C. Anderson

Dept. of Food & Animal Sciences, Alabama A&M Univ. P.O Box 1628, Normal, AL 35762-1628
This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Paper 67C-32. Presented at the Institute of Food Technologists Annual Meeting, Las Vegas, NV, July 14, 2004.

Abstract

Microwave blanching of fruits and vegetables has been identified as a process that retains nutrients better than conventional blanching methods (boiling water and steam). Only low energy level (500-700 Watt) microwaves using selected vegetables have been investigated in the past. Further studies are necessary to determine the effect of today’s higher energy level microwaves on the blanching of vegetables.

Yellow squash was blanched in covered containers for 3 min using: boiling water (BW), steam (ST), and 3 microwaves (1000 watt - MW1, 1200 watt - MW2, and 1300 watt - MW3). Samples were ice-cooled, placed in freezer bags, and stored at –18°C for 6 months. Enzyme activity, physico/chemical, nutritional and sensory parameters were assessed during and following 6 months of frozen storage.

Peroxidase (POD) activity decreased from 2.77-4.03 units (unblanched - UB) to 0.005-0.138 units after initial blanching. The MW3 treatment retained 96% Fe (170 mg/kg) and 93% K (2133 mg/kg), which was significantly higher than the other microwave blanch treatments. Total ascorbic acid (TAA) retention was highest (14.4 mg/100g) for the ST blanched treatment (97%). There were no significant TAA retention differences among the MW3 and ST treatments. Texture values were least firm for the BW treatment (66 Newtons) due to an increased cooking effect. Sensory preference scores indicated a level of acceptance that was no different from the commercial (control) product.

The study indicated that the overall quality of MW (all 3 energy levels) blanched yellow squash was as good as or superior to BW and ST blanching methods. The availability of this and other such information to home preservers of fruits and vegetables could lead to a higher quality of products for consumption.

Introduction

Microwave ovens are now being employed for meal preparation and food preservation instead of conventional stove top and conventional oven approaches.

Most vegetables require a short heat treatment called blanching. It is the primary means of inactivating oxidative enzymes present in vegetables and fruits in order to preserve quality prior to and during freezing and for reducing the surface microbial load. Blanching also aids in removing tissue gases, shrinking the product, peeling, cleaning and stabilizing color.

Conventional blanching processes utilize rapidly boiling water or steam as a heating medium and result in leaching of solids which reduces nutritional quality (Brewer, 2002).

Twenty-first century microwave blanching has proven to be 1) the most economically efficient, 2) better at retaining the nutrient content of treated fruits and vegetables, and 3) a better time saving method for the home preparation of vegetables for freezing (Barlow, 1998). Since over 93% of United States households own a microwave (IMPI, 2003), it is imperative that microwave blanching as a form of food preparation for home freezing be researched and usage guidelines communicated to the public.

Objective

The goal of this study was to compare the effects of microwave blanching of yellow squash utilizing three levels of microwave energy (MW1, MW2 and MW3) with those of conventional blanching (BW and ST). The objective of this study was to assess enzyme activity, chemical, physical, nutritional and sensory parameters following 6 months of frozen storage of microwave blanched yellow squash.

Materials and Methods

Sample Preparation

Yellow squash was harvested fresh in mid July. The vegetables were rinsed with tap water three times (to remove dirt and debris), blanched, and assayed for peroxidase activity within 4 hr of harvest. Yellow squash (200 g samples) was blanched for 3 min by three methods in covered containers using the required amounts of water: BW (1900 mL), ST (300 mL), and MW1, MW2, & MW3 (60 mL). Blanching time and proportion of vegetable/water were based on average times for BW and ST recommendations. MW blanch time was established in a previous study. This was the microwave blanch time required to inactivate POD activity. The vegetables were then ice-cooled for 5 min and drained. Samples were removed and packed in 1-L plastic freezer bags until further analyses.

Analyses

Peroxidase activity, minerals (calcium, iron, potassium and sodium), total ascorbic acid and texture of unblanched and blanched yellow squash were determined. Sensory evaluation was determined after 6 months on frozen and cooked yellow squash.

Peroxidase (POD) Activity
POD activity was determined spectrophotometrically as described by Chance and Maehly (1955) & revised by Sigma-Aldrich (1994). Absorbance (420 nm) was read at 20 sec intervals for 3 min. The unblanched vegetable was used as the control. Enzyme activity was expressed as units POD/mL vegetable filtrate.

Minerals (Ca, Fe, K and Na)
A microwave-assisted acid digestion procedure for preparing samples (based on US EPA Method 3051 for soil analysis and modified for appropriate foods) was used to prepare the vegetable samples for analyses (Pingitore, 1996). The digestate was analyzed using Inductively Coupled Plasma (ICP) Spectrometry and concentrations expressed in mg/kg (SW- 846, 1994).

Total Ascorbic Acid (TAA)
TAA was determined by HPLC using a UV detector set at 272 nm. The analytical column was a 250 x 4.6 mm x ¼ in Valco Microsorb (MV100-5) column. The method described by Russell (1986) was utilized for this experiment. The mobile phase consisted of 9.5% acetonitrile in DD water, 0.4 L/L ammonium hydroxide, 0.95 g/L hexane sulfonic acid (pH to 2.8 with phosphoric acid). Concentration of TAA was expressed as mg/100g.

Texture
A TMS-Texturepress (model FTA-300 Force Transducer) was used for texture evaluation. Homogeneous samples of chopped, unblanched & blanched vegetables (15 g) were used to fill the Allo-Kramer ten blade test cell (Model CS-2 Thin Blade Shear-Compression). A one-bite mode test was performed on each sample (Ponne, 1994; Bourne, 2002). The transducer cal number was 780 and the transducer speed was set to 1. Texture was determined as maximum force and expressed in Newtons (N).

Sensory
A 30 or more member consumer sensory panel (Alabama A&M University faculty, staff and students) used the Multiple-Paired Comparison Test to evaluate the single attribute, preference. Commercial frozen yellow squash was used as the control versus the other 5 blanch treatments for this characteristic. Sensory evaluation was conducted only on cooked yellow squash after 6 months of frozen storage (Meilgaard et al., 1999).

Statistical Analyses

Data were analyzed by ANOVA (analysis of variance) and significant different (p<0.05) means were determined using Tukey's HSD test (SAS, 2001). Values were reported as the mean of the four replicates.

Statistical analysis for sensory evaluation used Friedman's analysis T test (Meilgaard et al, 1999). Significant differences (p<0.05) were determined using Tukey’s HSD test.

Results and Discussion

POD enzyme activity in fresh, unblanched yellow squash varied from 2.77-4.03 units to 0.005-0.138 units after initial blanching. POD activity was retarded the most for MW1, MW2, MW3 and BW treatments at initial blanching and after 4 and 6 months frozen storage. Essentially, no POD regeneration occurred for all blanching treatments (Figure 1). The ST treatment was significantly higher (p&0.05) than the other blanching treatments for POD activity.
 

Enzyme Activity (units POD/mL filtrate)

Treatments

Figure 1. POD Enzyme Activity of Yellow Squash at Initial Blanching and after 4 and 6 Months Frozen Storage

Minerals

MW3 blanch treatment retained 94% Ca (197 mg/kg), 96% Fe (170 mg/kg), 99% K (2133mg/kg) and 69% Na (82 mg/kg) for yellow squash. The MW3 blanch treatment was significantly greater for potassium retention compared to the other microwave blanch treatments. There were no differences in the blanch treatments for calcium retention, but the MW3 blanch treatment was significantly greater than the BW and ST blanch treatments for iron and sodium retention (Table 1).
 

Table 1. Mineral Retention in Yellow Squash Originally and after 6 Months Frozen Storage 

Total Ascorbic Acid retention was highest for the ST blanch treatment (97%, 14.4 mg/100g) followed by the MW3 blanch treatment (87%, 12.9 mg/100g). MW1 and MW2 blanch treatments were significantly less in TAA retention than the MW3 blanch treatment but equivalent to the BW blanch treatment (Figure 2).
 

TAA (mg/100g)

Treatments

Figure 2. Total Ascorbic Acid Retention in Unblanched and Blanched Yellow Squash after 6 Months Frozen Storage

Texture

Unblanched yellow squash shear force was 128 N at initial measurement. Texture was firmest for the ST blanched treatment (106 N) and least firm for the BW blanched treatment (66 N) after initial blanching (Figure 3). There were no significant textural differences (p>0.05) among the three MW and ST treatments at initial blanch and after 4 months frozen storage.

Shear Force (Newtons/15g)

Treatments

Figure 3. Shear Force Resistance of Unblanched and Blanched Yellow Squash at all Storage Phases

Sensory Evaluation

The results revealed that after 6 months frozen storage, there were no significant differences in preference among the treatments (MW1, MW2, MW3, BW, ST and Control).

Conclusion

The three MW blanch and BW blanch treatments decreased POD activity better than the ST blanch treatment. Mineral losses may be attributed to interactions with other chemical compounds and large volumes of water used in the BW blanch treatment. TAA losses during the blanching process occurred mostly by leaching of soluble solids or aqueous extraction rather than by chemical degradation. Also, Ball (1997) stated that ascorbic acid oxidase and lipoxidase present in squash can oxidize TAA by generating free radicals from the oxidation of polyunsaturated fatty acids, which in turn can react with and damage TAA. This could also explain some TAA loss in yellow squash. Texture shear force values were least firm for the BW blanch treatment which was probably due to a greater cooking effect caused by greater amounts of heat produced by boiling water. The preference scores for this experiment indicated that a level of acceptance that was not different from the commercial (control) vegetable.

The study indicated that the overall quality of MW blanched yellow squash for all three energy levels was as good as or superior to BW or ST blanched methods. These microwaves when used as a preparatory blanching step for freezing of yellow squash could yield a higher quality product for the home consumer.

Selected References

• Bourne, M.C. (ed). 2002. Food texture and viscosity: concept and measurement. 2nd ed. Academic Press, San Diego, CA.
• Chance, B. & Maehly, A.C. 1955. Methods in Enzymology. 2:773-775.
• EPA Method 3051. 1994. From SW-846 Online. http://www.epa.gov/epaoswer/hazwaste/test/3series.htm.
• Meilgaard, M. et al. 1999. Sensory Evaluation Techniques, 3rd Ed., CRC Press, Inc., Boca Raton, FL.
• Pingitore, N.E. et al. 1996. The Border Basket: Analysis of Toxic Metals in Retail Foods, El Paso-Juarez. SCERP Project # EHPP961VI-2. The Univ. of Texas at El Paso.
• Russell, L.F. 1986. J. Food Science, 51(6):1567-68.
• Sigma-Aldrich, Inc. 1994. Enzymatic assay of Peroxidase (EC 1.11.1.7). Sigma quality control test procedure for Sigma product P-1432.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and Alabama A&M University receive acknowledgment and this notice is included:

Reprinted with permission of Alabama A&M University. J. Roberts, L. T. Walker and J.C. Anderson. 2004. Assessment of Microwave Blanching as a Preparatory Tool for Home Freezing of Yellow Squash. Normal, AL: Alabama A&M University, Food and Animal Sciences Department.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

E. M. D’Sa¹, E. L. Andress¹, J. A. Harrison¹ and M. A. Harrison². (1) Department of Foods & Nutrition Extension, (2) Department of Food Science & Technology, The University of Georgia, Athens, GA 30602-4356

Paper 020D-06. Presented at the Institute of Food Technologists Annual Meeting, Orlando, FL, June 26, 2006.

Abstract

Canning techniques for specialty foods like fruit curds are currently highly requested by home-canners. In recommending a home-canning process to consumers, the issue of primary concern to the Extension educator is to ensure a microbiologically safe, high-quality shelf-stable product.
The objective was to experimentally calculate a boiling water thermal process and determine the effect of consumer procedural variation on heat penetration patterns of lemon curd.
A standardized lemon curd formulation (equilibrium pH 3.7) was hot-filled into half-pint home canning jars. The cold spot was determined with Ecklund Harrison copper-constantan thermocouples, inserted through lids, monitoring product temperatures at four potential cold spots in sixteen canner loads. Sealed jars were placed in the canner and temperatures recorded using EllabTM software, through come-up, cool down, and a processing time that heated all jars to a minimum of 2°C below canner temperature. Analyses of f(h) values (slope of the straight line portion of a heating curve) located the cold spot at the geometric center of the jar. Cold-spot temperatures were then monitored through confirmation canning processes that produced a minimum final temperature of 90.5°C, for both standard filling and low-initial temperature filling variations. f(h) values were used to calculate the effect of consumer-induced procedural changes on the thermal process. A boiling water process recommendation of 15 min was calculated for this product. Up to a 15 minute post-cook delay prior to filling jars did not significantly change f(h) values when compared with the standard treatments.
Confidence in science-based thermal processing recommendations is essential for novel home-canned food products that are similar to commercially available high-demand items. A 15 minute boiling water heat process for this lemon curd ensures a safe, shelf-stable product. This study produced a research-based home-canning recommendation for a highly sought-after, distinct product category.

Introduction

Expanding food markets catering to eclectic tastes have made available a plethora of specialty food products, encompassing new forms of local foods, as well as various ethnic and international items. Lemon curd, a mixture of eggs, butter, lemon juice and sugar that results in a tart, sauce-like product is much coveted by epicures worldwide. Numerous and persistent requests for a safe USDA-recommended home-canning process for this category of foods prompted this research (Andress, 2001).
The objective of this project was to develop a high-quality product, determine an adequate thermal process for home-canned lemon curd, and to study the effect of consumer procedural variation on the thermal process. Since this is an acid product, the primary concern was to ensure the development of a safe, standardized product, to prevent spoilage from acid-resistant microorganisms during storage, and to recommend a shelf-life for the developed lemon curd.

Ingredients and Preparation Process

Lemon Curd:
Ingredients: 2½ cups superfine sugar*, ½ cup lemon zest (freshly zested), optional, 1 cup bottled lemon juice**, ¾ cup unsalted butter, chilled, cut into approximately ¾" pieces, 7 large egg yolks, 4 large whole eggs

Yield: About 3-4 half-pint jars.

* If superfine sugar is not available, run granulated sugar through a grinder or food processor for 1 minute, let settle, and use in place of superfine sugar. Do not use powdered sugar.
** Bottled lemon juice is used to standardize acidity. Fresh lemon juice can vary in acidity and is not recommended.

Procedure:

1. Wash 4 half-pint canning jars with warm, soapy water. Rinse well; keep hot until ready to fill. Prepare canning lids according to manufacturer's directions. Fill boiling water canner with enough water to cover the filled jars by 1-2 inches. Use a thermometer to preheat the water to 180°F. Caution: Do not heat the water in the canner to more than 180°F before jars are added. If the water in the canner is too hot, the process time will not be sufficiently long. The time it takes for the canner to reach boiling after the jars are added is expected to be 25 to 30 minutes for this product. Process time starts after the water in the canner comes to a full boil over the tops of the jars.
2. Combine sugar and lemon zest in a small bowl, stir to mix, set aside about 30 minutes. Pre-measure lemon juice and prepare the chilled butter pieces. Heat water in the bottom pan of the double boiler until it boils gently. The water should not boil vigorously or touch the bottom of the top double boiler pan or bowl in which the curd is to be cooked. Steam produced will be sufficient for the cooking process to occur.
3. In the top of the double boiler, whisk the egg yolks and whole eggs together thoroughly. Slowly whisk in the sugar and zest, blending until smooth. Blend in the lemon juice and add butter pieces to the mixture. Place the top of the double boiler over boiling water in the bottom pan. Stir gently but continuously with a silicone spatula or cooking spoon, to prevent the mixture from sticking to the bottom of the pan. Continue cooking until the mixture reaches a temperature of 170°F. Use a food thermometer to monitor the temperature.
4. Remove the double boiler pan from the stove and place on a dish cloth or towel on the counter top. Continue to stir gently until the curd thickens (about 5 minutes). Strain curd through a mesh strainer into a glass or stainless steel bowl; discard zest. Fill hot strained curd into the clean, hot half-pint jars, leaving ½-inch headspace. Remove air bubbles and adjust headspace if needed. Wipe rims of jars with a dampened, clean paper towel; apply two-piece metal canning lids.
5. Process in the prepared boiling water canner for 15 minutes (elevations up to 1000 ft). Cool, undisturbed, for 12-24 hours & check for seals.

Preparation Notes

Shelf- life: For best quality, store in a cool, dark place, away from light. Use canned lemon curd within 3 -4 months. Browning and/or separation may occur with longer storage; discard any time these changes are observed.

Variation: For Lime Curd, use the same recipe but substitute 1 cup bottled lime juice and ¼ cup fresh lime zest for the lemon juice and zest.

Thermal Process Development

Determination of the cold spot for this product and jar combination was made using data collected for heat penetration curves at 4 potential cold spot locations in the jars in 16 canner loads (see Table 1).
Procedural variation based on a pre-fill lag time was used in testing for process calculations. Temperature profiles were compared for fill temperatures (direct-fill, and after a 15 minute wait), which had means of 55.80° and 46.66°C, respectively. Process calculation was accomplished by using thermocouples in each of six jars in different canner loads of each of the two fill methods (standard, and low initial temperature). These jars were processed to 90.5°C plus an additional 5 minutes. Processing was done in a boiling water canner using the stovetop burners of a household gas range (Frigidaire Gallery Model ES III). Data was recorded using an Ellab E-ValTM Monitoring System and Software, and Ecklund needle Type T copper-constantan thermocouples. Analysis of variance was used to determine if significant (p<.001) differences existed between the treatments using the General Linear Model procedure in SAS 9.1 (2002-2003).

Results

Cold Spot Location

• The cold spot for this product and jar (half-pint) combination was located at the geometric center of the jar (Table 1).
• The f(h) value is the number of minutes it takes the straight line portion of the heat penetration plot to pass through one logarithmic cycle.
• A larger f(h) represents a slower rate of heat penetration, and is indicative of the location of the cold spot in that jar.

Thermal Characteristics of Jars Processed by Two Procedures

• The initial canner temperature was consistently maintained at 80.35-82.31°C prior to the loading of filled jars (Table 2).
• The initial temperature for this product as prepared and filled into jars by usual home canning practices ranged from 54.36-56.88°C in the standard series and 45.23° - 47.65°C in the LIT (low initial temperature series).
• Thus there was slightly greater variability among initial temperatures in the standard series, but this did not affect the interpretation of findings or the ultimate process recommendation.

Table 2: Thermal Characteristics of Jars Processed by Two Methods

Determination of the Calculated Thermal Process

• Pflug(1998) outlines guidelines for thermal process calculations, based on the equilibrium pH of the product. This is then correlated to a  in minutes, based on product pH. Since the equilibrium pH of the lemon curd product is 3.7, according to process development guidelines a minimum  of 0.1 minutes is enough to ensure an appropriately canned product.
• The  of 0.1 minutes for the lemon curd is achieved within 10-11 minutes from the start of process time (i.e. 10-11 minutes after come–up time).
• Thus, a 15 minute process time was determined for the product, this time would be sufficient to achieve the desired lethality, as well as ensure a proper vacuum seal for the jar lid and sterilization of the glass jar (Table 3).
• The shorter the come-up time, the longer it takes for the  of 0.1 minutes to be reached, regardless of f(h). Hence, it is essential for this particular process, to specify in process instructions, that the initial canner temperature should be 82°C. This allows the requisite come-up time to be achieved, and the accompanying  of 0.1 minutes to be achieved well within the recommended process time for this product.

Effect of Fill Weight and Initial Jar Temperature

• A 15 minute pre-fill cooling time (which resulted in a mean 9°C temperature difference) had no significant effect on f(h) values and thus the thermal process, for the lemon curd product in half-pint jars.
• The procedural variation of lowered initial jar temperature had no significant effect on the final product temperature at the end of the process.
• A 9°C decrease in fill temperature did not significantly change the number of minutes at boiling for the cold spot to reach 90.5°C (Table 4).

Table 4: Effect of Fill Temperature on Heat Penetration of Lemon Curd in Half-pint Jars

Summary and Conclusions

• A pre-fill lag period of up to 15 minutes did not change the heat penetration rate (fh) or processing time for this product.
• Canning instructions should be specific for the product composition, jar dimensions, and fill weight of jars.
• With this style product, initial canner temperature is a critical influence on the time taken to achieve process lethality.

References

This project was partially funded through a grant from the National Integrated food Safety Initiative (Grant No. 00-51110-9762) of the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. E. M. D’Sa, E. L. Andress, J. A. Harrison and M. A. Harrison. 2006. Thermal Process Development to Ensure the Safety of a Home-Canned Lemon Curd Product. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

E. M. D'Sa and E. L. Andress. Dept. of Foods & Nutrition Extension, University of Georgia, 208 Hoke Smith Annex, Athens, GA 30602.

Paper 020D-07. Presented at the Institute of Food Technologists Annual Meeting, Orlando, FL, June 26, 2006.

Abstract

Sugar substitutes are important in controlling calorie intake for consumers with health problems including obesity and diabetes. Among these, Splenda® (sucralose) is popular and suitable for inclusion in heat processed products. Consumer driven demands for safe, acceptable, shelf-stable home-canned fruit containing sugar substitute, necessitated a research based recommendation for home canned peaches containing Splenda®.
The objective was to recommend a process for peaches canned in Splenda® sugar substitute, based on product development and analysis of consumer sensory preferences.
Selected ‘Ruston Red’ peaches were canned in water, medium sugar syrup, full-strength ‘medium’ Splenda® syrup and half-strength ‘medium’ Splenda® syrup, using the USDA boiling water process for peaches. Physicochemical characteristics of fresh, canned and pre-consumption peaches were recorded, including pH, firmness, titratable acidity, percent soluble solids, and color. Peaches were stored in a temperature-monitored environment for 15 months and a consumer preference study followed. 42 respondents indicated their preferences for each sample using a 9-point hedonic scale and took a short survey providing information about their food preparation and consumption practices. Attributes scored included appearance, color, aroma, flavor, texture, sweetness, tartness, aftertaste and overall acceptability.
Overall acceptability was highest for peaches canned in sugar syrup, followed by full strength Splenda®, half strength Splenda®, and lastly, water. Full-strength Splenda® rated higher than half strength Splenda® on appearance, color, aroma, flavor, and texture while the half strength product scored higher on tartness and sweetness. There was no difference in aftertaste detection between the two. One-third respondents would be willing to buy either Splenda® product. The products were acid, hence suitable for boiling water canning.
A safe process for home-canning peaches using a sugar substitute is both timely and necessary. This study provides a research- and consumer-endorsed home-canning recommendation for peaches canned with medium strength Splenda® syrup that is both safe and acceptable.

Introduction

Home-canning of home-grown or locally purchased produce is a popular practice in the U.S (Andress, 2001). Abundant availability of summer fruits, especially peaches, prompts consumers to preserve these through canning. However, increasingly, a demand (fueled by health concerns about obesity and diabetes) has arisen for alternatives to sugar used in home-canned foods. The objective of this project was to develop a high-quality home-canned peach product using a non-nutritive sweetener, and to carry out a consumer preference study to determine the ideal level of sweetener to be added. Storage monitoring of the product determined the shelf-life that would be recommended for this product.

Materials and Methods

Canning Methods: The USDA recommended Boiling Water process for home canning peaches was followed (USDA, 1994). ‘Ruston Red’ Elberta-type peaches ideal for cooking were obtained from a local peach orchard (Washington Farms, Watkinsville, GA). The peaches were sorted for quality and ripeness. Care was taken to maintain equivalency in peach ripeness stage (assessed by tactile firmness).

1. The peaches were washed and hand-peeled, cut into halves, and the pits removed. Peach quarters were soaked in an ascorbic acid solution (3000 mg/gallon water) until used, to prevent darkening.
2. Four types of covering liquid were used. The solutions were prepared by dissolving the sweetener in water and heating until dissolved. The packing liquids include:
   • water
   • medium strength (30%) sugar syrup (1¾ cups sugar per quart water)
   • full-strength ‘medium’ Splenda® syrup (1¾ cups Splenda® per quart water)
   • half-strength ‘medium’ Splenda® syrup (7/8 cup Splenda® per quart water)
3. Peaches were hot-packed (brought to a boil in covering liquid from above) into prepared quart home canning jars. Canning lids were prepared according to manufacturer’s directions. Headspace was adjusted to ½ inch, air bubbles were removed and lids applied. Jars were processed for 25 minutes (elevations up to 1,000 ft) in a Boiling Water Bath canner on a household gas range (Frigidaire Gallery Model ES III). Jars were cooled, undisturbed, for 12-24 hours & seals were checked. Jars were stored in covered boxes for 15 months in a temperature-monitored environment maintained at 65°F.
4. Physical and chemical characteristics of fresh and canned peaches were measured:
         firmness – Penetrometer Fruit Pressure Tester QA Supplies, Model FT 327
         pH – Orion 520 A+ pH meter
         titratable acidity
         % soluble solids – Leica Abbe Mark II Refractometer Model 13104940
         color - Hunter Miniscan XE plus

Sensory Analysis

A Consumer Sensory Preference study was conducted with 42 respondents including University students, staff and faculty. A 9-point Hedonic scale was used for the respondents to score several attributes (see Table 1) for each of the 4 canned peach products mentioned above.

Respondents also answered a questionnaire that covered their fruit consumption and buying practices; home-canning experience; use of sugar substitutes, and demographic questions.

Results

Sensory Preferences

Figure 1: Overall Sensory Acceptability Scores of Panelists for Four Canned Peach Products

Significant Characteristics of Sensory Preferences

• The product with sugar obtained the highest scores for all positive attributes (Table 1).
• The ‘full-strength’ Splenda® product received higher scores for 6/9 attributes as compared to ‘half-strength’ Splenda® .
• For ‘Overall Acceptability’, the preference order was Sugar  ‘Full-strength’ Splenda®  ‘Half-strength’ Splenda®  Water.
• A strong product delineation was seen in the ‘Buying Inclination’ category, where 73.8% respondents indicated that they would buy the ‘full-sugar’ product, 33.3% indicated that they would buy the ‘full-strength’ Splenda® product, but there was a strong negative buying inclination towards the ‘water’ product (85.7%), and the ‘half-strength’ Splenda® (40.5%) product. This indicates that consumers do not want to compromise on the quality factors in their purchase of canned fruit.

Demographic Results

• 88% respondents (37/42) were female
• 52.38% (22/42) were employed full-time
• 45.23% (19/42) were students
• 76.19% (32/42) were natives of GA
• 2 each from Michigan and Tennessee
• and one each from SC, FL AK, NV, IN, China

Figure 2: Age Range of Respondents

Fruit Canning and Consumption Practices of Respondents

Conclusions

• Both full-strength ‘medium’ Splenda® syrup and half-strength ‘medium’ Splenda® syrup are suitable for use in home-canning peaches. However, ‘full-strength’ is preferred overall by most consumers participating in a Sensory Preference study. The ‘standard’ sugar syrup product was the most preferred, and the product canned in water was the least preferred.
• Peaches canned with Splenda® using the USDA canning instructions for fruit retain quality and shelf life for at least one year when stored under recommended conditions, between 50-70°F, in a dry place away from strong light.

References

This project was partially funded through a grant from the National Integrated food Safety Initiative (Grant No. 00-51110-9762) of the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture.

The authors acknowledge Dr. Ruthann Swanson, Department of Foods & Nutrition, University of Georgia, for her assistance with the experimental design of the Sensory Preference study.

Document Use:

Permission is granted to reproduce these materials in whole or in part for educational purposes only (not for profit beyond the cost of reproduction) provided the authors and the University of Georgia receive acknowledgment and this notice is included:

Reprinted with permission of the University of Georgia. E. M. D'sa and E. L. Andress. 2006. Developing a Recommendation for Home-Canned Peaches with a Sucralose Sugar Substitute. Athens, GA: The University of Georgia, Cooperative Extension Service.

References to commercials products, services, and information is made with the understanding that no discrimination is intended and no endorsement by the University of Georgia, U.S. Department of Agriculture and supporting organizations is implied. This information is provided for the educational information and convenience of the reader.

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability. An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force.

Contact:

National Center for Home Food Preservation
208 Hoke Smith Annex
The University of Georgia
Athens, GA 30602-4356

Tel: (706) 542-3773
Fax: (706) 542-1979
Web: http://www.homefoodpreservation.com

E. M. D’Sa1, E. L. Andress1, J. A. Harrison1 and M. A. Harrison2.
(1) Department of Foods & Nutrition Extension, (2) Department of Food Science & Technology, The University of Georgia, Athens, GA 30602-4356

Paper 005-04. Presented at the Institute of Food Technologists Annual Meeting, Chicago, IL, July 29, 2007.

Abstract

The use of science-based, tested processes is critical to the safety of home-canned foods. A national survey was conducted to determine consumer knowledge and practice of home canning techniques. Results indicate a critical need for education and increased awareness of safety-related concerns. The objective was to identify food safety concerns in the practice of home canning, and to compare these results with those from a previous survey (year 2001). A 2005 national telephone survey of U.S. adults was conducted, using a 42-item questionnaire about consumers’ home canning knowledge and habits. 801 complete interviews were obtained from randomly selected households across the nation, with a 95% confidence level and a 30% cooperation rate. Survey results indicate that about one in five households canned foods in 2004. The most popular sources of instructions continue to be family or friends (51.2%, earlier 48%) and cookbooks (16.7%, earlier 19%). 30.5% altered recommended canning procedures. Most commonly canned foods were vegetables (64.9%, earlier 71%) and tomato products (59.2%, earlier 60%). 9.2% used non-nutritive sweeteners in jams or jellies, with sucralose being most popular. The risky practice of open-kettle canning (hot fills only) is still practiced for fruits and tomatoes (44% of canners), vegetables (35.4%) and meats or seafood (20%). 32% (earlier 38%) of all canners had jars that did not seal properly, and 35.6% (earlier 37%) stored their home-canned foods for longer than 12 months. Education about and reinforcement of science-based food preservation resources are essential in promoting safe home-canning techniques. Failure to use recommendations can result in foodborne illness including botulism, or food spoilage. These survey results identify current critical areas of concern in U.S. consumer canning practices, and therefore provide guidelines for continued Extension-based efforts in this area.

Introduction

Home food preservation methods continue to be key interest areas for consumers wanting to use the abundance from their home gardens or local markets to have homemade specialties all year. Preserving this food safely while maximizing food quality are essential features of Extension food preservation recommendations. Home canning continues to be a popular means of preserving food at home (Andress, 2002). The importance of safe home canning practices must be emphasized. Using unsafe practices could lead to occurrence of foodborne illness (including the potentially fatal botulism), or, at the very least, food spoilage.

This national telephone survey conducted in 2005 was aimed at determining consumers’ home canning and home food preservation knowledge and practices, and identifying potential areas of food safety concern. Results obtained from this survey will also be compared with the results of a similar 2001 national telephone survey. Areas of similarity or divergence between the two surveys will be documented.

Objectives

To conduct a randomly-based national survey of U.S. households practicing home food preservation techniques on a routine basis

• To determine consumer knowledge of safe home canning techniques.
• To identify types and quantities of foods being canned at home.
• To identify potential unsafe home canning practices that need to be targeted by Extension communicators.

Methods

A questionnaire was developed by researchers at the National Center for Home Food Preservation and the Survey Research Center, University of Georgia, that was translated into a 91-item (42 closed- or open-ended item canning survey) instrument. Respondents could choose more than one appropriate response for some questions. Between April 4 and June 16, 2005, a national telephone survey of adults was conducted. Telephone interviewers received training and practice in areas of survey purpose, methods, standard telephone interviewing procedures; and were supervised at all times to ensure quality control. A total of 8,848 numbers were called; and 2, 676 eligible interviewees were contacted. This yielded 801 complete interviews, of which 174 respondents canned foods at home. It is the data from this group of 174 respondents that is being analyzed in this presentation. 

In order to reduce bias in response and draw accurate inferences from the adult population, sampling procedures utilized ensured that all households had near-equal selection chances for inclusion in the sample. A 95% confidence interval and a sampling error of +/- 5% insured that estimates produced were precise and accurate. A 30% cooperation rate was obtained, and one-fifth to one-quarter of all interviews were monitored.  

Results

Who is canning?

• 22% of respondents completing the full interview reported canning food at home during the 2004 canning season; 79% of these planned to can food the following season. These numbers are somewhat lower (27%, 91% respectively) when compared with the 2001 survey.
• 58% (earlier 49%) of home canners are between 35-64 years of age; 27% (earlier 23%) are 65 and over, and 15% (earlier 24%) are under 35 (Figure 1). 
• 76% of respondents were female (earlier 82%) and 51% (earlier 52%) were employed during the preceding year, either year- round (77%, earlier 72%), for 26-51 weeks (15%, earlier 21%) or for less than 26 weeks (8%, 4% earlier).
• Most home canners have at least a high school education; 28% (both surveys) have at least a 4-yr college degree (Figure 2). 
• Less than half (41%) of home canners live in 2-4 person households (Figure 3). 60% (both surveys) of these households had no individuals under the age of 18 yrs, while 15% (earlier 19%) had one under-18 yr old, and 17% (earlier 8%) had either 2 or 3 under-18s.
• Participation in home canning does not appear to be related to income, but there was a fairly high non-response rate (48%, earlier 41%) to this question (Figure 4).
• 84.5% (earlier 84%) of respondents were “White”, 5% (earlier 6%) African-American, less than 1% were Asian/Pacific Islander, about 1% were Native American/Alaskan Native, and 6% described themselves as multi-racial. About 5% of respondents were of Hispanic origin.

What are their sources of information?

• Family or friends (51%), generic cookbooks (17%), directions from pressure cooker manufacturer (13%), Ball Blue Book (7.5%), directions from canning jar/lid manufacturers (7%), magazines or newspapers (4%), Extension Service (3%), the Internet (3%), community cannery instructions (0.5%) and “other” (13%).
  • In comparison, the 2001 survey results showed that the top information categories were also friends or relatives (49%) and generic cookbooks (19%), followed by directions from canning jar/lid manufacturers (10%), directions from pressure cooker manufacturers (9%), USDA publications (3%), Extension Service (2%) and “other” (25%).
• 55% of respondents (earlier 67%) used their canning instructions “as is”, while 30.5% (earlier 29%) adapted the instructions for their personal use. 

What are they canning and how?

• 65% canned vegetables (71% earlier), 59% canned tomatoes/tomato products (60% earlier), 52% canned fruit (47% earlier) and 65% canned pickled products.  Of those canning pickles, 20% used firming treatments, with salt water soak (22%), pickling lime (13%), ice water soak (13%), and Pickle Crisp® (9%) being the most popular firming treatments.
• Non-nutritive sweeteners were used by some home canners in jams/jellies/preserves (9.2%), fruits (6.32%), and pickles/relishes/salsas (1.15%). Within this group, Splenda® (sucralose) was the most popular (used by 42%), followed by Sweet’n Low® (21%), Equal® (5%) & Sweet One® (5%).
• Figure 5 represents the canning methods used by respondents who canned fruits and tomatoes, vegetables and meats/poultry/seafood. Table 1 represents a breakdown of the types and quantities of food items canned by respondents.

Equipment Use and Management

• Only 12% of respondents had the dial gauge on their pressure canner tested in 2004. 11% have a pressure canner without a dial gauge. Of those who had the dial gauge tested, 12.5% (2) had it tested at the Extension Service, 25% (4) at a hardware store and 6.25% (1) at a utility company. (Note: Extension agents often test pressure canner dial gauges at hardware stores.)
• 16% of respondents reported making elevation adjustments when using their pressure canners, while 10% reported making elevation adjustments when using a boiling water canner.
• 49% of respondents used an electric range for home canning, 24% used a gas range, 15.5% used an electric smooth-top range and 1% used sealed gas burners.

Jars and Lids

• Approximately 64% of respondents (earlier 74%) used home canning jars with 2-piece lids, 10% used home canning jars with other lids, 2.3% used recycled jars from commercially canned foods, 7% used the older home canning jars with rubber rings, 7.5% respondents used metal cans.
• 32% of respondents reported having jars that did not seal properly after canning. For the jars that did not seal, 20% reprocessed them, 37.5% refrigerated and consumed them quickly, about 4% froze the contents of the jars for later consumption, and 43% discarded the contents.

Food Use, Storage and Spoilage

• 11.5% of respondents reported serving the home canned food as is, with no heating, 30% brought the food to a boil before serving, 21% boiled the food for 10 minutes or more, 24% warmed the food on a stovetop, oven or microwave, 19% used the canned food as an ingredient in other recipes, 7% steamed the food, and 3% used “other” means of preparation.
• How long do they store the canned food? 18% reported using the home canned food within 6 months, 42.5% stored the food for 6-12 months, and 36% reported storing the food for more than 1 year.
• What are the signs that canned food (home canned or commercially-canned) is spoiled? 86% recognized a bulging lid as a sign of spoilage, 84% mentioned “mold”, 83% mentioned “off-odor”, 78% mentioned “off-color”, 76% mentioned “leakage”, 56% mentioned “spurting liquid when container is opened” and 44% mentioned “floating fruit or vegetables” as a sign of spoilage.
• Only 45% of respondents thought that home canned foods could be spoiled without obvious signs of spoilage, and 12% reported that their home canned food from the 2004 canning season had spoiled.

Summary and Conclusions

• There is similarity between the results of the 2001 and 2005 surveys in some areas, but not all. The lack of consistent use of science-based home canning techniques and equipment among home canners continues to be a disturbing observation.
• Family and friends continue to be the largest category source of instructions for home canning recommendations. Greater     use of USDA and Extension sources for recommendations would be a highly desirable shift in this observation. Mobilizing      County Extension and community efforts in this area, coupled with greater publicity given to existing USDA recommendations, is a way to change this trend.
• Also disturbing is the continued use of unsafe home canning methods like oven canning, open-kettle canning, and the use of boiling water canning for low-acid foods. Again, education and information dissemination in this area should be emphasized.     

References

1.  Andress et al., 2002. Current Home Canning Practices in the U.S. Institute of Food Technologists Annual Meeting Presentation, Paper 46B-3.
2.  Bason, J. 2006. Materials and Methods Statement. Survey Research Center, The University of Georgia, Athens, GA.
3.  Bason, J. 2001. Materials and Methods Statement. Survey Research Center, The University of Georgia, Athens, GA

This project was partially funded through a grant from the National Integrated food Safety Initiative (Grant No. 00-51110-9762) of the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture.

To maintain good natural color and flavor in stored canned food, you must:

• Remove oxygen from food tissues and jars,
• Quickly destroy the food enzymes,
• Obtain high jar vacuums and airtight jar seals.

Follow these guidelines to ensure that your canned foods retain optimum colors and flavors during processing and storage:

• Use only high-quality foods which are at the proper maturity and are free of diseases and bruises.
• Use the hot-pack method, especially with acid foods to be processed in boiling water
• Don't unnecessarily expose prepared foods to air. Can them as soon as possible.
• While preparing a canner load of jars, keep peeled, halved, quartered, sliced, or diced apples, apricots, nectarines, peaches, and pears in a solution of 3 grams (3,000 milligrams) ascorbic acid to 1 gallon of cold water. This procedure is also useful in maintaining the natural color of mushrooms and potatoes, and for preventing stem-end discoloration in cherries and grapes. You can get ascorbic acid in several forms:

  Pure powdered form – seasonally available among canners' supplies in supermarkets. One level teaspoon of pure powder weighs about 3 grams. Use 1 teaspoon per gallon of water as a treatment solution.

  Vitamin C tablets – economical and available year-round in many stores. Buy 500-milligram tablets; crush and dissolve six tablets per gallon of water as a treatment solution.

  Commercially prepared mixes of ascorbic and citric acid – seasonally available among canners' supplies in supermarkets. Sometimes citric acid powder is sold in supermarkets, but it is less effective in controlling discoloration. If you choose to use these products, follow the manufacturer's directions.

• Fill hot foods into jars and adjust headspace as specified in recipes.
• Tighten screw bands securely, but if you are especially strong, not as tightly as possible.
• Process and cool jars.
• Store the jars in a relatively cool, dark place, preferably between 50°F and 70°F.
• Can no more food than you will use within a year.

Adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, NIFA-USDA (Revised 2015).

U.S. Department of Agriculture
Food Safety and Inspection Service (USDA-FSIS)

• Focus on: Freezing
• Focus on: Sausages
• Food Safety of Jerky
• Mail Order Food Safety
• Refrigeration and Food Safety
• Menu of USDA food safety and preparation publications

U.S. Food and Drug Administration
Center for Food Safety and Applied Nutrition (FDA-CFSAN)

• Approximate pH of Foods and Food Products
• Safe Handling of Produce
• Information for Processors of Acidified and Low-Acid Canned Foods

United Nations
Food and Agricultural Organization (UN-FAO)
These publications provide an educational review of topics for an international audience and should not be used for recommendations or guidelines for home food preservation in the United States.

• Fermented fruits and vegetables. A global perspective. 1998.
• Fruit and vegetable processing. 1995. 390 pp.
• Guidelines for small-scale fruit and vegetable processors. 1997. 195 pp.
• Small-scale sausage production. 1985. 

Menu with Spanish language factsheets as well as the English versions

Elaboración de conservas de tomates y productos de tomates (Canning Tomatoes and Tomato Products)

Guardado de frutas en conserva (Canning Fruits)

Guardado de vegetales en conserva (Canning Vegetables)

Recetas de salsa para guardar en conserva (Salsa Recipes for Canning)

The publications below provide a sampling of information on special topics that might also be of interest.  You should also check with other state university's Extension programs, especially in your own state, to see if additional information is available.

Colorado State University

• Cost of Preserving and Storing Food
• Understanding and Making Kimchi

New Mexico State University

• Home Canned Sweet Spreads Made with Green Chile

North Carolina State University

• Botulism and Home Canned Green Beans
• Botulism and Home Canned Beets

North Dakota State University

• Jams and Jellies from North Dakota Fruits

Oregon State University

• Freezing Convenience Foods That You've Prepared at Home
• Canning Seafood
• Home Canning Smoked Fish
• Smoking Fish at Home - Safely

Penn State University

• A series of "Let's Preserve" factsheets on many topics, such individual fruit and vegetable topics, fruit pie fillings, meat and poultry, pickles and sauerkraut.

University of California, Davis

• Garlic - Safe Methods to Store, Preserve, and Enjoy
• Olives - Safe Methods for Home Pickling
• Harvesting and Storing your Home Orchard's Nut Crop: Almonds, Walnuts, Pecans, Pistachios, and Chestnuts
• Also see UC-Davis Consumer Home Preservation for more resources and their Food-Specific Resources on Home Food Preservation 

University of Idaho

• Making Garlic- and Herb-Infused Oils at Home

Utah State University

• A Guide to Food Storage for Emergencies

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About This Site

This site was developed by the National Center for Home Food Processing and Preservation (NCHFP) at the University of Georgia, with funding from Cooperative State Research, Education and Extension Service, United States Department of Agriculture (CSREES-USDA).  It is expanded and maintained by the NCHFP at the University of Georgia with funding from the National Institute of Food and Agriculture, USDA (NIFA-USDA).

Website Administrator

Jimmy Hansen

The University of Georgia
200 Dawson Hall
Athens, GA 30605

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The National Center for Home Food Processing and Preservation project team is doing its best to provide users with accurate information. However, neither this project team, The University of Georgia nor the USDA are responsible for any information which may be incorrect . It is particularly advisable to check with the original author or a local expert when seeking advice or interpretation of regulations and other legal materials.

It is our intention that the specific contents of this website may be printed and copied for not-for-profit personal and educational use. If extracts from this website are posted to other sites, the responsibility for accuracy and updating of the information becomes that of the site which adopts the information. In addition, if information from this website is extracted for use, credit is to be given to the author of the original document along with a statement to the effect that the information came from the National Center for Home Food Preservation website.

The use of trade, firm, or corporation names in this website and links to information on outside, commercial websites is for the educational information and convenience of the reader. Such use does not constitute an official endorsement or approval from the United States Department of Agriculture, The University of Georgia, or this project team of any product or service to the exclusion of others that may be suitable.

Website Accessibility Statement

The National Center for Home Food Preservation is committed to making all of its information on this site available to all extension agents, consumers, professionals, educators, and employees of the Center. The Web site for the Center is constantly being evaluated to meet the requirements of Section 508 of the Rehabilitation Act of 1973 and the W3C's Web Content Accessibility Guidelines 1.0. The University of Georgia's text transcoder service may be utilized to provide a text-only version of the Web site to accommodate individuals with visual impairments. This site is designed to be compatible with most current browsers (minimum browser recommendation: Netscape 3.0, Internet Explorer 4.0, Opera 5.0, and Amaya 3.0). Note: Possible issues with the formatting of tabular data may occur in text-only browsers (i.e. Lynx).

Some information on this site requires the use of plugins. Real Player is required to view the So Easy to Preserve video clips. A free version of this plugin can be downloaded from the Real Web site. Slide shows on the site are in Microsoft PowerPoint format. A free PowerPoint viewer can be downloaded at the Microsoft Web site. Macromedia Flash Player is required to view the Basics of Food Preservation tutorial series. This free plugin can be downloaded from the Macromedia Web site. Also, Adobe Acrobat Reader is required to view the publications which are in the PDF format. This free plugin can be downloaded from the Adobe Web site. Adobe also offers a Web-based service which can convert many PDF files to html or text. The Center also attempts to provide content of multimedia files in an alternate html or text file when necessary.

If you have questions or comments about this site or need to request information in an alternative format (for disabilities), please contact the Website Administrator at nchfp@uga.edu.

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Projects

Projects of the Center, 2011-2015

Outreach/Communications

• Developing, implementing and evaluating a series of six youth lesson plans on home food preservation. See: https://nchfp.uga.edu/putitup.html
• Developing, implementing and evaluating a series of six youth lesson plans on home food preservation.
• Developing and teaching webinars on home food preservation.
• Building website resources and maintaining the integrity of current website content.

Research

• Conducting laboratory research on atmospheric steam canning for acid foods. See: Using Atmospheric Steam Canners
• Conducting applied laboratory research to compare several home canning lid systems on features of sealing rates and vacuums obtained.
• Conducting laboratory research on atmospheric steam canning for acid foods.

Projects of the Center, 2005-2010

Research

• Conducting applied laboratory research on a partially-fermented, refrigerator-stored dill pickle procedure to describe any potential heating treatments for Listeria risk.
• Conducting applied laboratory research on a home-canned tomato-based salsa procedure.

Outreach/Communications

• Developing, implementing and evaluating 4 additional website-based self-study course modules.

Instruction

• Developing, implementing and evaluating an undergraduate college short-course about home food preservation.

Projects of the Center, 2000-2005

Activities of the National Center addressed goals for providing scientific, research-based recommendations for home food processing and preservation to the public. The activities included research, publications and development of communication and outreach strategies. Here's a sampling:

Research

• Scanning the scientific literature, reviewing and synthesizing findings, and creating electronic databases of the literature and reviews.
• Conducting research on microbial safety of various procedures and ingredients to develop recommendations for new products to add to our home canning and other preservation databases.
• Conducting microbial challenge studies of some historical processes to validate their safety in light of newer food safety knowledge.
• Conducting new research on microwave blanching of vegetables.

Outreach/Communications

• Updating the NIFA-USDA Complete Guide to Home Canning. (The version released December 2009)
• Developing a website to represent the wealth of information from USDA and the national Cooperative Extension System, and the National Center. (www.homefoodpreservation.com)
• Developing a model Master Food Preserver curriculum and teacher manual.
• Developing on-line instructional presentations about the science of food preservation and an on-line course for educators. (Had been available on this website; is being moved to new platform in 2017.)
• Producing an instructional video series for home food preservation educators (i.e., an updating of the University of Georgia's So Easy to Preserve series). (Ordering information available at www.soeasytopreserve.com)

Instruction

• The Center has employed graduate students in Food Science and Foods and Nutrition/Dietetics from the University of Georgia and Alabama A&M University. These students learned about home food preservation and conducted some of the research described above.

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For canning and other food preservation recommendations, please use the website first.

Search

For NCHFP resource and content questions, please email foodpres@uga.edu. The Center is undergoing some staffing changes but you will receive a response from educators at the University of Georgia.

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Project Team

The University of Georgia

Beginning 2021

Interim Coordinator

• Tracey Brigman, EdD, MS, RDN, LD, Clinical Assistant Professor and Interim FACS Coordinator of Food Safety and Preservation

Through 2020

Project Director

• Elizabeth L. Andress, Ph.D., Professor and Extension Food Safety Specialist (retired)

Co-Investigators

• Judy A. Harrison, Ph.D., Professor and Extension Foods Specialist (retired)
• Mark A. Harrison, Ph.D., Professor, Food Science and Technology (retired)

Staff

• Kasey A. Christian, M.Ed., Program Assistant (until October 2015)
• Jimmy Hansen, Website Administrator

Collaborators, 2011-2014

• Susan F. Barefoot, Ph.D., Program Leader, Food Safety, Nutrition and Health, Clemson University
• Barbara H. Ingham, Ph.D., Associate Professor and Extension Food Science Specialist, University of Wisconsin-Madison
• Mark R. Etzel, Ph.D., Professor, Food Science and Chemical Engineering, University of Wisconsin-Madison

Appreciation to all former staff and collaborators, including:

Collaborators, 2005-2010

University of Georgia

• Elaine M. D'Sa, Ph.D., Research Coordinator
• Jimmy Hansen, Website Administrator

Advisory Committee, 2005-2008

• Susan K. Hovey, M.S., Union County Cooperative Extension Service, Clemson University
• Barbara Ingham, Ph.D., Associate Professor and Extension Food Science Specialist, University of Wisconsin-Madison
• Patricia A. Kendall, Ph.D., R.D., Professor and Food Safety Extension Specialist, Colorado State University
• Robin A. Orr, Ph.D., Extension Specialist/EFNEP/FNP, University of Illinois
• Jananne Finck, M.S., R.D., Extension Educator, Nutrition and Wellness, Springfield Center, University of Illinois

Collaborators, 2000-2005

University of Georgia

• William L. Kerr, Ph.D., Associate Professor, Food Science and Technology (Co-Investigator)
• Anne L. Sweaney, Ph.D., Professor, Housing and Consumer Economics (Team Member)
• Brian A. Nummer, Ph.D., Foods and Nutrition (Project Staff)

Alabama A&M University

• Lloyd T. Walker, Ph.D., Associate Professor and Interim Chair, Food and Animal Sciences
• John C. Anderson, Ph.D., Associate Professor, Food and Animal Sciences

University of California-Davis

• Linda Harris, Ph.D., Associate Cooperative Extension Specialist, Food Sciences and Technology

University of Puerto Rico-Mayagüez

• Edna Negrón, Ph.D., Professor and Head of Department, Food Science and Technology

Advisory Committee, 2000-2005

University/Cooperative Extension

• Evelyn F. Crayton, Ed.D., R.D., L.D., Professor and Extension Foods and Nutrition Specialist, Auburn University
• Angela Fraser, Ph.D., Assistant Professor and Extension Food Safety Specialist, North Carolina State University
• Linda Harris, Ph.D., Extension Food Safety/Microbiology Specialist, University of California-Davis
• Virginia Hillers, Ph.D., Professor and Extension, Washington State University
• Elizabeth Hoyle, M.S., Professor and Extension Food Specialist, Clemson University
• Patricia Kendall, Ph.D., R.D., Professor and Food Safety Extension Specialist, Colorado State University
• Karen Penner, Ph.D., Professor and Extension Specialist, Food Science, Kansas State University
• Donna Scott, M.S., Food Safety Specialist and Senior Extension Associate, Cornell University
• Christina Stark, M.S., R.D., Extension Nutrition Specialist, Cornell University

Industry

• Judy L. Harrold, Manager, Consumer Affairs, Alltrista Consumer Products Company
• Jo Anne O’Gara, Home Economist, National Presto Industries, Inc.

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Home food preservation remains an important and popular cultural activity. It is critical that those who practice preserving and processing foods at home have access to the most reliable information available concerning food safety and food quality. The Cooperative Extension System (CES) and USDA have long been recognized as credible sources for science-based recommendations. However, developmental work on new or continued recommendations has been sporadic since the 1950s due to availability of resources and probably interested persons. Two national surveys conducted by the Center in 2000 and 2005 both revealed a high percentage of home food processors are using practices that put them at high risk for foodborne illness and/or economic losses due to food spoilage.

The National Center for Home Food Processing and Preservation was established with funding from the Cooperative State Research, Education and Extension Service (CSREES-USDA) in 2000 as a multi-institutional effort with The University of Georgia and Alabama A&M University as the primary institutions. Expert scientists in home food preservation from industry and eight other U.S. universities comprised an advisory committee for the Center.  Home food preservation recommendations were updated through laboratory development and testing of products and critical literature reviews; recommendations from USDA and the Cooperative Extension System have been made available through this website; a new video series; on online self-study course; revision of the USDA Complete Guide to Home Canning (2009 and 2015); updating of Extension professionals in various states; and, various other publications on the website.

The first project ended in 2005, but the Center received additional funding to conduct some additional limited projects through August 2010. Collaborators from 5 states were part of the National Center team for those years, but primarily through 2008.  In 2005-2010, work continued on the website-based self-study course modules; applied laboratory research on refrigerator dill pickles and canned tomato-based salsas was conducted; and, an undergraduate college short-course about home food preservation was developed, implemented and evaluated.

The last project, 2011-2015, developed, implemented and evaluated a series of six youth lesson plans on home food preservation; developed and taught webinars on home food preservation; and, built our website resources and maintained the integrity of current website content.  In addition, research was conducted on atmospheric steam canning for acid foods and to compare several home canning lid systems on features of sealing rates and vacuums obtained.

There has not been funding of the National Center since 2015 for any new projects or dedicated staffing.

This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2011-51110-30995.

This work has also been supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreements No. 00-51110-9762 and 2005-51110-03283.

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All Abstracts for presentations are presented in PDF format. Presentations are currently provided in PowerPoint and HTML format (those that are not in html format currently are in the process of being converted).

These papers represent research or other information presented in a scientific or association professional meeting format. They do not by themselves represent USDA or NCHFP recommendations for consumer food preservation at home. In many cases, they represent research in process. For our recommendations on how to preserve food at home, please see our other publications, or the How Do I.... sections of this Web site.

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2001

Document Use | Preface | Table of Contents | References

6. Critical Preservation Points

These guidelines have been created by the NCHFP using the 2001 Food Code, which are recommendations created by the United States Public Health Service, Food and Drug Administration (PHS/FDA 2001), and other published science-based recommendations as referenced. The guidelines have been reviewed by the National Center for Home Food Preservation’s Advisory Board and external experts. Adhering to these guidelines will minimize the risk of exposure to food poisoning organisms. 

6.1. General Guidelines

6.1.1. Sanitation

All equipment, work surfaces, and utensils should be cleaned and sanitized before and after use (PHS/FDA 2001). An example of a sanitizing solution for home use is 1 tablespoon of chlorine bleach in a gallon of warm water (Marchello and Garden-Robinson 1998). Cross contamination between raw and/or dirty surfaces with clean or cooked food products should be of prime concern.

6.1.2. Storage/Refrigeration

During storage or refrigeration, raw products must be separated from cooked products. Never store raw products above or in contact with cooked products (PHS/FDA 2001). If necessary, place raw products in pans or utensils approximately 1-2” deep to keep meat juices from contacting with other surfaces.

6.1.3. Temperature

The danger zone for microbial growth is 40-140°F (USDA FSIS 1997b). Therefore, store, age, cure, or otherwise preserve meats in a refrigerator below 40°F. Cooking meats to an internal temperature of 160°F will destroy bacteria that can cause foodborne illness (USDA FSIS 1997b). Any recipe that minimizes preservation time within the temperature danger zone followed by cooking to a safe internal temperature will minimize risks of food poisoning.

6.2. Curing Guidelines

6.2.1. Meats

Meat must be fresh prior to applying any preservation method. Curing should not be used to salvage meat that has excessive bacterial growth or spoilage (PHS/FDA 2001). Meat, especially game meat, does not need to be aged, since curing/smoking will act to tenderize it. If aging is desired, age all meats below 40°F. (Cutter 2000).

6.2.2. Salt.

Only food grade salt without additives, e.g., iodine, should be used. Using salt with impurities can produce less desirable results, especially with fish (Turner, no date). Thawing must be monitored and controlled to ensure thoroughness and to prevent temperature abuse. Improperly thawed meat could cause insufficient cure penetration. Temperature abuse can allow spoilage or growth of pathogens (PHS/FDA 2001).

6.2.3. Curing Compounds

Purchase commercially prepared cure mixes and follow instructions carefully (PHS/FDA 2001) or blend cure mixes carefully at home using an accurate scale.

Nitrate. Use cure mixtures that contain nitrate (e.g., Prague Powder 2, Insta-Cure 2) for dry-cured products that are not to be cooked, smoked, or refrigerated (PHS/FDA 2001). Dry cure using 3.5 oz. nitrate per 100 lbs. meat maximum or wet cure at a maximum of 700 ppm nitrates (9 CFR Cpt 3. 318.7(c)(4), 381.147(d)(4)).

Nitrite. Use cure mixtures that contain nitrite (e.g., Prague Powder 1, Insta-Cure 1) for all meats that require cooking, smoking, or canning (PHS/FDA 2001). Dry cure using 1 oz. nitrite per 100 lbs. meat maximum. For sausages use ¼ oz. per 100 lbs. (Reynolds and Schuler 1982). A 120 ppm concentration is usually sufficient and is the maximum allowed in bacon (PHS/FDA 2001).

Nitrites are toxic if used in quantities higher than recommended; therefore caution should be used in their storage and use (PHS/FDA 2001). About 1 g or 14mg/kg body weight sodium nitrite is a lethal dose to an adult human (USDA FSIS 1997b). Mistakenly using sodium nitrite instead of NaCl in typical curing recipes can lead to a lethal dose of nitrite in the incorrectly cured product (Borchert and Cassens 1998). For this reason it is safer to purchase and use curing mixtures rather than pure nitrites (saltpeter).

6.2.4. Cure Penetration

Cure mixtures do not penetrate into frozen meats. Before curing, it is essential to thaw meats completely first in the refrigerator. Pieces must be prepared to uniform sizes to ensure uniform cure penetration. This is extremely critical for dry and immersion curing (PHS/FDA 2001). Use an approved recipe for determining the exact amount of curing formulation to be used for a specified weight of meat or meat mixture (PHS/FDA 2001). All surfaces of meat must be rotated and rubbed at intervals of sufficient frequency to ensure cure penetration when a dry curing method is used (PHS/FDA 2001). Immersion curing requires periodic mixing of the batch to facilitate uniform curing (PHS/FDA 2001). Curing should be carried out at a temperature between 35°F and 40°F. The lower temperature is set for the purpose of ensuring cure penetration and the upper temperature is set to limit microbial growth (PHS/FDA 2001). Curing solutions must be discarded unless they remain with the same batch of product during its entire curing process –because of the possibility of bacterial growth and cross-contamination, do not reuse brine (PHS/FDA 2001).

6.3. Smoking

Verify that smokehouses operate as intended (heat, airflow, moisture). Appropriate calibrated thermometers should be used (for cooking temperature and meat internal temperature). Procedures for delivering the appropriate thermal treatment of cooked meats in conformance with the Food Code must be developed and used. Smoke itself, without proper cooking, is not an effective food preservative (Hilderbrand 1999). Caution should be used when smoking meats at temperatures in the danger zone 40-140°F for prolonged periods of time. In such a case meats must have been salted or cured first.

6.3.1. Smoke Cooking

Consumers should smoke cook foods to internal temperatures as listed by the USDA (USDA-FSIS 1999).

6.3.2. Cooling

Cool cooked products rapidly to below 40°F and keep refrigerated. Cooked fish products should generally be cooled from to 70°F or below within 2 hours and to 40°F or below within another 4 hours (US FDA 1998). Minimize handling of cooked products. Dry (unfermented) products may not be hot smoked until the curing and drying procedures are completed. Semi dry fermented sausage must be heated after fermentation to a time/temperature sufficient to control growth of pathogenic and spoilage organisms of concern.

6.4. Trichinella

Pork products must be treated to destroy Trichinella by (a) Heat: A minimum internal temperature of 130°F(30 min.), 132°F(15 min.), 134°F(6 min.), or 136°F(3 min.), (b) Freezing: 5°F(20 days), -10°F(10 days) or -20°F(6 days) for all pork in pieces not exceeding 6 cu. inches. Double the freezing times for larger pieces up to 27 inches of thickness or (c) some combination of curing, drying, and smoking can kill Trichinella, but these are process specific (9 CFR 318.10).

FSIS approved of the use of up to 50% KCl2 in place of NaCl for the destruction of trichinae (USDA FSIS 1995c). Wild game (bear, elk, etc.) must be treated to destroy Trichinella by heating to 170°F, since some strains of Trichinella are freeze resistant (CDC 1985).

6.5. Fish

Intentionally under-processed fish (e.g., green herring, or cold smoked fish) should be frozen first to 4°Ffor 7 days to kill parasites (PHS/FDA 2001) or to -10°Ffor at least 7 days (Price and Tom 1995). Because spores of C. botulinum are known to be present in the viscera of fish, any fish product that will be preserved using salt, drying, pickling, or fermentation must be eviscerated prior to processing. Without evisceration, toxin formation is possible during the process. Small fish, less than 5 inches (12.7 cm) in length, that are processed in a manner that prevents toxin formation, and that reach a water phase salt content of 10%, a water activity of below 0.85, or a pH of 4.6 or less are exempt from the evisceration requirement (US FDA 1998). For salted and hot smoked fish, use brine with a minimum salt concentration of 3.5% water phase salt (Hilderbrand 1999). It is not recommended to hot or cold-smoke fish that have not been brined (Schafer 1999).

6.6. Ham Recommendations

For country ham, dry salt cured ham, country cured shoulder ham, or dry-cured bacon, the internal salt content should be 4% when used with nitrates/nitrites or 10% without the use of nitrates/nitrites. Properly prepared dry cured hams are safe to store at room temperature (Reynolds et al., In Press, PHS/FDA 2001). Soak country cured hams in water in the refrigerator (40°F) to reduce salt levels prior to eating (PHS/FDA 2001). High humidity during curing and aging may lead to surface spoilage. Mold may grow on the surface and can be safely washed off.

6.7. Sausage

All recipes should call for final internal temperatures that will destroy trichinae. We do not recommend preparing homemade, non-fermented sausages that are not fully cooked. If you do prepare them, be sure the meat, especially pork, has been properly frozen to destroy trichinae and other parasites. Use a meat thermometer to help insure that meat is kept cold before cooking and that sausage is properly cooked. Cool the sausage quickly after cooking and keep in the refrigerator for short term storage or freezer for long term storage (Busboom 1996). Semi-dry cured sausages, such as summer sausage, should be heat treated to 145°F for 4 minutes to destroy E. coli that may have survived the curing and fermentation process (USDA FSIS 1995).

6.8. Storage Guidelines

Store Cured/Smoked Poultry up to two weeks in the refrigerator or up to one year in the freezer (TAES Extension Poultry Scientists 1999). Store lightly cured fish 10-14 days in the refrigerator or 2-3 months in the freezer (Luick 1998). Vacuum packaged meats, e.g., smoked fish, must be kept at 40°F, since the reduced oxygen atmosphere increases the risk of botulism poisoning (Luick 1998). Modern fish curing/smoking recipes produce a highly perishable product that rarely keeps better than the raw fish.

6.9. At Risk Consumers

You can protect your unborn child by not eating shark, swordfish, king mackerel, and tilefish that can contain high levels of methylmercury (U.S. F.D.A. 2001a). "At risk" consumers should avoid eating refrigerated smoked seafood, unless it is in a cooked dish. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna, or mackerel, is most often in recipes for "Nova style, "lox, kippered, smoked or jerky seafood. These preparations are at risk for Listeria monocytogenes contamination (U.S. F.D.A. 2001b). At-risk consumers might want to avoid dry cured sausages because of the risk of E. coli O157:H7 (USDA FSIS 1995b). Consumers may want to avoid feeding cured products containing nitrates/nitrites to babies less than three months old because of implications in Sudden Infant Death Syndrome (SIDS) due to nitrate/nitrite poisoning (methemoglobinemia).

Document Use | Preface | Table of Contents | References

Document Use | Preface | Table of Contents | References

5. Food Safety of Cured and Smoked Meats

5.1. Food Safety Concerns

Concern for food safety has arisen over: (1) the public’s desire for variety and healthfulness that leads them to both non-traditional foods and non-traditional processes that may lack research into their safety and (2) the emergence of new foodborne diseases that challenge the safety of traditional food preservation methods. Bacteria, yeasts and molds find meat a suitable substrate for growth, resulting in meat quality and safety deterioration. Foodborne diseases are mostly of bacterial origin and meat has been implicated in roughly one third of the foodborne outbreaks in North America (Saucier 1999). The pathogenic microorganisms representing the greatest risk with meat and poultry borne diseases are Salmonella spp., Campylobacter spp., verotoxigenic Escherichia coli, Listeria monocytogenes and Toxoplasma gondii (Saucier 1999). Consumers and home food preservers should be warned that microorganisms are ubiquitous in the environment and that pathogens may survive traditional and non-traditional food preservation techniques if they are improperly processed (Bruhn 1997).

5.1.1. Non-traditional foods and non-traditional processes

Today, consumers demand foods that are minimally processed, as "natural" as possible, and yet are convenient to use. Complicating these factors is a consumer preference toward cured and smoked foods that are processed with lower salt, lower nitrate and higher moisture levels. These parameters have a tremendous impact on the safety of a given cured/smoked food or process. Preferences for low fat and low sugar have less impact on the safety, but these factors can change the traditional curing and smoking process. It will be difficult to completely eliminate the use of nitrite, as there is no known substitute for it as a curing agent for meat. Nonetheless, the demand for fewer chemicals added to foods has put pressure on the industry and the scientific community to seek new alternatives.

In-home vacuum packaging machines have become popular in recent years. It is important to realize that in-home vacuum packaging is not a substitution for cooking or any form of food preservation, e.g., refrigeration, freezing, or curing (Andress 2001). In-home vacuum packaging can reduce the quality deterioration of foods catalyzed by oxygen, such as rancidity. Many food spoilage and food poisoning organisms require oxygen for growth and would also be inhibited by this process. However, the most deadly food poisoning organism, Clostridium botulinum requires a low oxygen atmosphere and therefore, vacuum packaging favors its growth (Andress 2001). In cured meats, careful attention must be paid to proper use of nitrates/nitrites that inhibit Clostridium botulinum prior to use of in-home vacuum packagers. To further reduce the risk of botulism after vacuum packaging, properly refrigerate the cured/smoked meats. Under normal processing, freezing of salt-cured meats is not recommended, due to oxidative rancidity that affects the quality and flavor of the product.

5.1.2. Emergence of new foodborne diseases

More than 200 known diseases are transmitted through food (Mead et al. 2000). The causes include viruses, bacteria, and parasites. Many of the pathogens causing foodborne illness were not recognized 20 years ago (Mead et al. 2000). Major emerging pathogens include Campylobacter jejuni, Salmonella, Listeria monocytogenes, and Escherichia coli O157:H7. Many emerging foodborne diseases can cause chronic and serious health problems (Mead et al. 2000).

5.2. Food Poisoning Organisms

Microorganisms are ubiquitous in foods. Some can be present and harmless. Others can be present and produce chemicals that alter the acceptability of the food, hence food spoilage. Lastly, microorganisms can be present where they themselves or the products they produce can cause food poisoning. Details on pathogenic organisms mentioned below can be found in the FDA Bad Bug Book (US FDA 1992).

5.2.1. Botulism

The majority (65%) of botulism cases are a result of inadequate home food processing or preservation (CDC 1998). Botulism results from ingestion of a toxin produced by the bacterium C. botulinum. This bacterium requires a moist, oxygen-free environment, low acidity (pH greater than 4.6) and temperatures in the danger zone (38-140°F) to grow and produce toxin. C. botulinum forms heat resistant spores that can become dangerous if allowed to germinate, grow, and produce toxin. Sufficient heat can be used to inactivate the toxin (180°F for 4 min., Kendall 1999). C. botulinum thrives in moist foods that are low in salt (less than 10%), particularly when they are stored at temperatures above 38°F. These organisms will not grow in an aerobic environment, but other aerobic organisms in a closed system can rapidly convert an aerobic environment to an anaerobic environment by using the oxygen for their own growth, permitting growth of C. botulinum.

1. For more information, please refer to the following resources:


2. Botulism in the United States, 1899 - 1996 (CDC 1998).
3. Potential Hazards in Cold Smoked Fish: Clostridium botulinum type E. (US FDA 2001c).
4. Botulism (Kendall 1999).

5.2.2. Clostridium perfringens

Spores of some strains of Clostridium perfringens are so heat resistant that they survive boiling for four or more hours. Furthermore, cooking drives off oxygen, kills competitive organisms, and heat-shocks the spores, all of which promote germination to vegetative or growing cells. Once the spores have germinated, a warm, moist, protein-rich environment with little or no oxygen is necessary for growth. If such conditions exist (i.e., incorrectly holding meats at warm room temperature for smoking), sufficient numbers of vegetative cells may be produced to cause illness upon ingestion of the contaminated meat product.

5.2.3. Listeria monocytogenes

L. monocytogenes has been found in fermented raw-meat sausages, raw and cooked poultry, raw meats (all types), and raw and smoked fish. Its ability to grow at temperatures as low as 3°C, permits multiplication in refrigerated foods. The organism grows in the pH range of 5.0 to 9.5 and is resistant to freezing. It is salt tolerant and relatively resistant to drying, but easily destroyed by heat. (It grows between 34 - 113°F).

1. For more information, please refer to the following resources:


2. Potential Hazards in Cold Smoked Fish: Listeria monocytogenes (US FDA 2001c).

5.2.4. E. coli O157:H7

Ground beef is the food most associated with E. coli O157:H7 outbreaks, but smoked and cured foods also have been implicated, including dry-cured salami, game meat, and homemade venison jerky. Studies have shown that E. coli O157:H7 can survive the typical dry fermentation processing conditions (Tilden and others 1996); E. coli O157:H7's tolerance of acidic conditions has also been reported in the processing of other foods such as apple cider and mayonnaise. These findings led to significant changes in the food industry and in the manufacturing of dry fermented sausage in the U.S. In August 1995, USDA/FSIS recommended using a heat process (145°F for 4 minutes) to inhibit E. coli O157:H7 growth in sausage (USDA FSIS 1995).

5.2.5. Trichinosis

Details on trichinosis can be found in a publication by the National Pork Producers Council (Gamble) and on trichinosis statistics in the USA (CDC 1988). Trichinosis is an infestation of trichinae, or Trichinella spiralis or other Trichinella spp. The parasites invade the muscles causing severe pain and edema. It can be avoided by ensuring that cooked pork or certain wild game meat reaches an internal temperature of 150°F or more. Freezing the pork according to the following chart also can kill trichinae:

Although the incidence of trichinosis has decreased markedly from 300 to 400 cases annually in the 1940's to less than 90 cases per year in the early 1980's, this disease remains a problem in the United States. According to USDA recommendations, T. spiralis in pork is rendered non-viable if held at 5°F, a temperature achievable in noncommercial freezers, for 20 days. However, meat from wild game, such as polar bear or walrus meat that has been infected with T. spiralis, remains infective even after 24 months of storage at 0°F. The difference in susceptibility may be caused by different strains of T. spiralis found in domestic versus wild animals. Adequate cooking (170°F. internally), well above the thermal death point of the organism (137°F), remains the best safeguard against trichinosis in game meats (CDC 1985).

5.2.6. Staphylococcus aureus

Staphylococcus is more salt-tolerant than most other bacteria. It is naturally present on human skin. Some species of Staphylococcus produce toxins that cause food poisoning. So, handling of cured meats with unwashed hands, followed by holding the food at warm temperatures (>40°F), can result in bacterial growth and toxin formation. While temperatures of 120ºF can kill the bacterium itself, its toxin is heat resistant; therefore, it is important to keep the Staphylococcus organism from growing in foods. Use proper food handling practices to avoid contact with potentially contaminated surfaces and materials. Keep food either hot (above 140°F) or cold (below 40°F) during serving time, and as quickly as possible, refrigerate or freeze leftovers and foods to be served later. Staphylococcus aureus is destroyed by cooking and other thermal processing, but can be reintroduced via mishandling; the bacteria can then produce a toxin that is not destroyed by further cooking. Dry curing may or may not destroy S. aureus, but the high salt content on the exterior of dry cured meats inhibits these bacteria. When the dry cured meat is sliced, the moist, lower salt interior will permit staphylococcal multiplication.

5.2.7. Salmonella

Salmonella outbreaks have been recorded for raw meats, poultry, and fish and beef jerky. Salmonella bacteria thrive at temperatures between 40-140°F. They are readily destroyed by cooking to 165°F and do not grow at refrigerator or freezer temperatures. They do survive refrigeration and freezing, however, and will begin to grow again once warmed to room temperature.

5.2.8. Campylobacter

Raw chicken is a primary source of this organism, which grows best in a reduced oxygen environment. It is easily killed by heat (120°F), is inhibited by acid, salt and drying, and will not multiply at temperatures below 85°F. Campylobacter is the leading bacterial cause of diarrhea in the U.S.

5.2.9. Vibrio

Infections with this organism have been associated with the consumption of raw, improperly cooked, or cooked and recontaminated fish and shellfish. A correlation exists between the probability of infection and warmer months of the year. Improper refrigeration of seafood contaminated with this organism will allow its proliferation, increasing the possibility of infection. People with liver disease are particularly at risk for infection caused by undercooked seafood containing V. vulnificus (US FDA CFSAN 1998).

5.2.10. Parasites (other than Trichinella)

Anisakis simplex parasites are known to occur frequently in the flesh of cod, haddock, fluke, pacific salmon, herring, flounder, and monkfish. However, only 10 reported cases annually in the U.S. are attributed to them. Diphyllobothrium latum and Nanophyetus spp. parasites are known to occur frequently in the flesh of fish. Foodborne illnesses attributed to them are few in number. Sufficient cooking of foods would destroy the parasites.

In the Great Lakes region of the U. S., the Broad Fish Tapeworm has resulted in food poisoning outbreaks related to pickled pike. The larvae pass through small fish until they hatch as small worms in larger fish. If consumed at this stage by humans the worms can grow in the intestines (Schafer 1990). Sufficient cooking of foods would destroy the parasites.

5.2.11. Viruses

Shellfish are the food most often implicated foods in outbreaks of viruses such as Norwalk and Hepatitis A. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with viruses. Sufficient cooking of foods would destroy the viruses.

5.3. Inhibition of Pathogens in Cured Meats

Salt and nitrates or nitrites are the primary chemicals that are responsible for the inhibition of pathogen growth when curing meats. Adding to that, pH and temperature (below 40°F or above 140°F), these factors can act in concert to prohibit the growth of pathogens in these foods. Table 5.3. indicates some extreme parameters for growth of pathogens.

5.4. Cured / Smoked Food Poisoning

5.4.1. Ham

Trichinella, Staphylococcus, and molds are the microorganisms most associated with ham. All ham should be processed to specifically kill trichinae (USDA FSIS 1995c). Staphylococcus aureus, which is salt tolerant, can survive the high salt levels of the ham surface. Once the ham is sliced, S. aureus can grow on the interior tissues where there is a lower salt concentration. Therefore, the USDA-FSIS recommends that all sliced ham be refrigerated (USDA FSIS 1995c). Molds can grow on the ham surface, especially on country-cured hams. The USDA-FSIS recommends that you wash the ham free of the mold with a stiff vegetable brush and that consumption of the ham is safe (USDA FSIS 1995c). We were unable to find any studies of aflatoxin formation with molds associated with hams.

1. For more information:


2. Outbreak of Type E Botulism associated with home-cured Ham Consumption (Rosetti et al. 1999).
3. Tainted ham suspected in deadly bacteria outbreak (Associated Press 1997).
4. Outbreak of Staphylococcal Food Poisoning Associated with Precooked Ham -- Florida, 1997 (CDC 1997b).

5.4.1. Bacon

Like other cured products, Listeria monocytogenes has been responsible for a number of recalls of ready-to-eat bacon, e.g., State of Ohio Department of Agriculture Recall Announcement (ODA/ODH) 99 05a. Packages stored at room temperature sampled positive for the pathogen.

5.4.2. Beef

Pastrami made in a small Idaho commercial firm tested positive for Listeria monocytogenes in July 2000. No reports of food poisonings were recorded, but the products were recalled (USDA FSIS 2000a). Corned beef samples also tested positive for Listeria monocytogenes from a Michigan commercial firm (USDA FSIS 2000b). Corned beef was cooked and temperature abused at a deli in Ohio resulting in an outbreak of C. perfringens food poisoning (CDC 1994).

1. For more information, please refer to the following resources:


2. Clostridium perfringens Gastroenteritis Associated with Corned Beef Served at St. Patrick's Day Meals -- Ohio and Virginia, 1993 (CDC 1994).

5.4.3. Poultry

Much of the reports of food poisoning and recalls of poultry products for have been with commercial ready to eat products, such as chicken or turkey lunchmeats.

5.4.4. Fish

Listeria monocytogenes has been found in commercial samples of cold smoked fish leading to product recalls in New York (Cold smoked sea bass FDA Recall No.F-313-1) and Seattle, WA (Cold smoked salmon FDA Recall #F-265-1). These recalls demonstrate that even with HACCP and careful plant sanitation, commercial processors have contamination incidences in their cold smoked fish processes. In New York, fish sausage was recalled because laboratory analysis found pH (acidity), salt and water activity levels in the product were such that they could potentially permit Clostridium botulinum to develop and produce the toxin (NY State Agriculture Commissioner 2000).

1. For more information, please refer to the following resources:


2. Uneviscerated Fish Products that are Salt cured, Dried, or Smoked (US FDA 2000).
3. International Outbreak of Type E Botulism Associated With Ungutted, Salted Whitefish (CDC 1987).
4. Vibrio parahaemolyticus Infections Associated with Eating Raw Oysters -- Pacific Northwest, 1997 (C.D.C. 1997c).
5. Vibrio vulnificans (US FDA CFSAN 1998).
6. Processing Parameters Needed to Control Pathogens in Cold Smoked Fish (US FDA 2001c).

5.4.5. Sausage

Recent concern about the safety of sausages has been in the semi-dry fermented sausages, such as summer sausage. E. coli O157:H7 has been found to survive the acidity of these products (Corlett 1998). Some commercial, ready-to-eat sausages and luncheon meats have been implicated in Listeria monocytogenes growth and outbreaks. Additional concerns with trichinae may occur in any pork sausage.

1. For more information, please refer to the following resources:


2. Pennsylvania Firm Recalls Lebanon Bologna Nationwide (Lombardi and Redding 1995).
3. Illness outbreak associated with Escherichia coli O157:H7 in Genoa salami (William and others 2000).
4. A new route of transmission for Escherichia coli: infection from dry fermented salami (Tilden and others 1996).
5. Interim Guidelines for the Control of Verotoxinogenic Escherichia coli Including E. coli O157:H7 in Ready to Eat Fermented Sausages Containing Beef or a Beef Product as an Ingredient: Guideline no. 12 (Health Products and Food Branch - Canada 2000).
6. Escherichia coli O157:H7 Outbreak Linked to Commercially Distributed Dry-Cured Salami -- Washington and California, 1994 (CDC 1994).

5.4.6. Game

Precaution should be used since venison, bear, elk, wild boar, wild turkey, rabbit and other game animals are usually field dressed in unknown sanitary conditions or kept from immediate refrigeration. Two areas of special interest should be noted: (1) E. coli O157:H7 outbreaks in game sausage and jerky, and (2) Trichinosis in game meats from northern U.S. areas (Zarnke and others 1997). Several outbreaks of E. coli O157:H7 have occurred in venison jerky (USDA FSIS 1998).

T. nativa is an Alaskan, Canadian, and Arctic strain of Trichinella that is freeze-resistant. Unlike pork, freezing arctic meat will not kill larval cysts. Wild game, e.g., bear or walrus meat, is safe once the entire piece is completely cooked. USDA recommends attaining an internal temperature of at least 170°F (CDC 1985). Since cooking may be uneven, microwaving of game meats is not recommended, (Zarnke and others 1997).

1. For more information, please refer to the following resources:


2. Five Cases of Trichinosis - Why Bear Meat Must Be Thoroughly Cooked (State of Alaska Epidemiology 2000).
3. E. coli Cases Associated with Wild Game Pepperoni (Idaho Central District Health Department 1999).
4. An outbreak of E. coli O157:H7 infections traced to jerky made from deer meat (Oregon Health Division 1997).

5.5. Cured/Smoked Food Spoilage

Not all microbial growth leads to food poisoning. Indeed, many organisms simply spoil cured and smoked foods making them unpalatable. Keep in mind that it is a general rule that if conditions exist to allow growth of spoilage organisms, these same conditions can allow for the growth of food poisoning organisms. Good judgment should prevail.

5.5.1. Lactic Acid Bacteria

Lactic acid bacteria are frequent spoilage organisms on cured/smoked meats. They are tolerant of some of the conditions in the curing/smoking process or are contaminates after processing. They grow slowly, but eventually spoil the food by producing organic acids.

5.5.2. Mold and Cured Meats

Moldy cured or smoked meat is a controversial topic. Very often country hams will have a moldy surface. Currently the USDA FSIS recommends cleaning the mold and soaking the ham in water to refresh it is a safe procedure (USDA FSIS 1995c). Other suggestions are to wash the ham in acetic acid (acetic acid Avinegar@ 10% in water; Marriott and Graham 2000).

5.5.3. Greening of Cured/Smoked Meats

Lactobacillus viridescens, or similar bacteria that produce hydrogen peroxide may cause greening in meats. The H2O2 reacts with myoglobin to produce a green sheen pigment. The meat, while less appealing, is not dangerous to consume.

5.5.4. Slime Producers

Some Micrococcus spp. and other bacteria are capable of producing slime on the surface of hams, bacon, and sausages.

5.5.5. Gas Producers

Some organisms can produce gas pockets inside cured and/or smoked meats.

5.5.6. Rancid Flavors in Home Cured Pork

Salt increases oxidation during long cures and can lead to a rancid flavor. Prolonged frozen storage may also contribute to oxidation leading to rancid flavors. Many consumers prefer these flavors. For those that do not, shorter curing and aging times should be considered (Marriott and Graham 2000).

1. For more information, please refer to the following resources:


2. Some Solutions To Difficulties of Home-Curing Pork (Marriott and Graham 2000).
3. Protecting Home-cured Meat from Insects and Mites (Townsend 1997).

Document Use | Preface | Table of Contents | References

Document Use | Preface | Table of Contents | References

4. Cured/Smoked Meats

4.1. Ham

Ham is cured pork from the hind leg of the hog. Picnic shoulder or picnic ham is made from the front leg of the hog (USDA FSIS 1995c). Ham varieties may or may not be smoked and are available in many regional and ethnic styles (Alden 2001b). Curing solutions for hams typically contain salt, sodium nitrate, sugar, and seasonings (USDA FSIS 1995c). Dry-cured ham includes country ham and proscuitto. The dry cure mixture is rubbed onto the pork surface and the meat is cured (at or below 40°F) from weeks to a year or more. During this aging process, the moisture is reduced by 18-25%, making these hams safe at room temperature (USDA FSIS 1995c). Brine-cured ham includes culatello and Irish Hams. Usually the fresh meat is both injected with brine and submerged into the brine to allow the cure to reach all of the meat (USDA FSIS 1995c).

1. For more information, please refer to the following resources:


2. Focus On: Ham (USDA FSIS 1995c).
3. Ham Glossary (Alden 2001b).
4. Dry-Curing Virginia style Hams (Marriot and Kelly 1998).

4.2. Bacon

Bacon is cured and/or smoked hog meat from the pig belly. Bacon produced at home, is typically dry-cured with salt, nitrites, sugar, and spices for a week or longer. Because of concern over N-nitrosamines, the use of nitrates for bacon curing is not allowed commercially (USDA FSIS 1997c). Home preparations, such as Morton Smoked-flavored sugar cure, contain nitrates and are recommended by the manufacturer for the use in bacon curing (Morton Salt Co.1996). Some ethnic bacon (Canadian bacon and Irish bacon) is made from leaner cuts. Pancetta is Italian bacon that is not smoked. Salt pork is salted pork belly fat.

1. For more information, please refer to the following resources:


2. Bacon Glossary (Alden 2001a).
3. Home Curing Bacon for a Mild Flavor (Alexander and Stringer 1993).

4.3. Beef

The most well known cured beef product is corned beef made from the beef brisket. Pastrami is smoked corned beef.

1. For more information, please refer to the following resources:


2. Focus On: Corned Beef (USDA FSIS 1995a).
3. Corned Beef the Easy Way (Reddish 1981).

4.4. Poultry

Any variety of poultry can be cured and/or smoked. Curing and smoking imparts a unique, delicate flavor and pink color to poultry meat. As with other meats, curing and smoking increases the refrigerated storage life of poultry. When preparing smoked poultry products, most consumers use mild cures (relatively low salt) to maintain the poultry flavor (Busboom 1997).

1. For more information, please refer to the following resources:


2. Curing and Smoking Poultry Meat (Busboom 1997).
3. Curing and Smoking Poultry (Mississippi State Extension Service 2000).
4. Curing and Smoking Poultry (TAES Extension Poultry Scientists 1999).
5. Smoking Poultry Meat (Miller and Enos 1998).

4.5. Fish

Any fish can be salted and smoked. Some varieties of fish make for better tasting products than others. Commercially, nitrite curing is only allowed for sable, salmon, shad, chub, and tuna in the U.S. (US FDA 2001c). Other species were never included in the Code of Federal Regulations simply because industry members did not respond to initial inquiries about GRAS (Generally Regarded as Safe) practices (Ken Hilderbrand, personal communication).

1. For more information, please refer to the following resources:


2. Smoking Fish at Home - A Step-by-Step Guide (Kassem 2001).
3. Home Canning Smoked Fish and Home Smoking Fish for Canning (Raab and Hilderbrand 1993).
4. Smoking Fish at Home (Luick 1998).
5. Fish Smoking Procedures for Forced Convection Smokehouses (Hilderbrand 2001).
6. Smoking Fish at Home--Safely (Hilderbrand 1999).
7. Smoking Fish (Price and Tom 1995).
8. Smoking Fish (Michigan State University Extension 1999a).
9. Smoking Fish in a Smokehouse (Michigan State University Extension 1999b).
10. Preserving Fish (Schafer 1990).
11. Cured Herring or Alewives (Michigan State University Extension 1999c).
12. Salting Fish (Turner 2001).
13. A Guide to Making Safe Smoked Fish (University of Wisconsin 1999).
14. Processing parameters needed to control pathogens in cold smoked fish (US FDA 2001c).

4.6. Sausage

Sausage can be made from any meat source, and is typically ground. Sausage can be uncured and unsmoked, but for the purposes of this document, we consider only cured and/or smoked sausage. Usually cure ingredients (salt, nitrates/nitrites, and spices) are mixed with the ground meat and stuffed into casings (animal intestines or collagen). The product is then cured for a short time (e.g. overnight for bologna) at refrigerated temperatures. It may or may not be smoked, dried, or fermented.

1. For more information, please refer to the following resources:


2. Focus On: Sausages (USDA FSIS 1995b).
3. Sausage Glossary (Alden 2001c).
4. The Art and Practice of Sausage Making (Marchello and Garden Robinson 1998).
5. Sausage and Charcuterie Glossary Terms (Unichef.com 2001).
6. Sausage and Smoked Meat (Reynolds and Schuler 1982).

4.7. Game

Venison, bear, elk, wild boar, wild turkey, rabbit and other game animals can be successfully cured/smoked.

1. For more information, please refer to the following resources:


2. Proper Processing of Wild Game and Fish (Cutter 2000).
3. Wild Side of the Menu No. 3 Preservation of Game Meats (Marchello and Beck 2001).
4. Preserving Game Meats (Hoyle 1999).

4.8. Links to Recipes from Cooperative Extension System Publications

The following is a list of cured/smoked meat recipes found in Cooperative Extension Service publications. The NCHFP has not reviewed or tested these recipes and provides their listing here only as a source for the reader. Individuals should evaluate the safety of the recipes using the recommendations provided in Section 6 of this publication.

4.8.1. Ham

Cured Ham and Bacon (Epley and Addis 1992). Dry-Curing Virginia style Hams (Marriot and Kelly 1998).

4.8.2. Bacon

Cured Ham and Bacon (Epley and Addis 1992). Home Curing Bacon for a Mild Flavor (Alexander and Stringer 1993).

4.8.3. Corned Beef and Meats

Corning (Epley and Addis 1990). Hot Pickle Cure Jerky (Marchello and Garden Robinson 1998).

4.8.4. Poultry

Poultry (Busboom 1997). [Curing and] Smoking Poultry (Miller and Enos 1998). Smoked/Cured Quail, Smoked Broilers (Mississippi State Extension Service 2000). Curing and Smoking Poultry (TAES Extension Poultry Scientists 1999).

4.8.5. Fish

Salting and Smoking Fish (Hilderbrand 1999). Brining and Smoking Fish at Home (Kassem 2001). Smoking fish at home (Luick 1998). Smoking Fish (Michigan State University Extension 1999a). Cured Herring or Alewives (Michigan State University Extension 1999c).

4.8.6. Sausage

Summer Sausage (Epley and Addis 1992). Braunschweiger, Polish Sausage, Smoked Bratwurst, Smoked Turkey and Pork Sausage, Emulsified Products [Hot Dogs] (Marchello and Garden Robinson 1998).

4.8.7. Game

Corning Game, Sweet Pickle Cure of Game, Venison Bologna, Venison Summer Sausage, Wild Game Polish Sausage (Cutter 2000). Dry-curing game, Sweet Pickle curing [Game], and Corning Game Meats (Hoyle 1999). Venison Garlic Sausage, Venison Summer Sausage (Marchello and Garden Robinson 1998). Dry Curing Game, Using Sweet Pickle Cure [Game](Marchello and Beck 2001).

Document Use | Preface | Table of Contents | References

Document Use | Preface | Table of Contents | References

3. Post Processing of Cured Foods

Cured meats can be consumed as is or undergo further processing to achieve a final product. Typically meats are smoked, fermented, or dried to complete the preservation process.

3.1. Smoking

The smoking process both preserves and flavors food. Hams, bacon, salmon, herring, and oysters are frequently smoked. It is important to make a distinction between smoking for preservation (smoke cooking) and smoking for texture and flavor. Generally there are three different methods of smoking foods: hot smoking and cold smoking.

3.1.1. Hot Smoking

Hot smoking is done in the smokehouse or more modern electric kilns, usually over a short period of time, just until the meat is cooked. The meat is cooked and smoked at the same time over a burning fire or electric elements of a kiln.

3.1.2. Cold Smoking

“Cold Smoking” is done over a much longer period of time, e.g. 12-24 hours, over a smoldering fire (below 85°F). Since foods are held in the temperature danger zone, rapid microbial growth (40-140°F) could occur. Therefore, only those meat products that have been fermented, salted, or cured, should be cold-smoked. Most cold-smoked products should be cooked to an internal temperature of 160°F before they are eaten. However, not all cold-smoked foods are treated this way, e.g., smoked salmon and cold smoked mackerel, which are very delicately smoked for a long period of time and remain raw even when eaten. The US FDA has published a description of a commercial cold smoking process (US FDA 2001c). Most food scientists cannot recommend cold-smoking methods because of the inherent risks and as such, at-risk consumers are encouraged to avoid these foods (US FDA 2001a).

3.1.3. Liquid Smoke

Many consumers and commercial operations use liquid smoke to add smoke flavor to their foods. Liquid smoke has advantages over traditional smoking in that it can be more precisely controlled and the smoke flavor is instantaneous.

3.2. Fermenting and Drying

Fermenting and drying, as food preservation methods, are covered in separate National Center for Home Food Preservation literature reviews. For the purposes of this review, some cured sausages are also fermented and dried, e.g., salami and pepperoni. Particular attention has been given to this category of sausage since it has been responsible for several food poisoning outbreaks that were generally regarded as low risk. Krizner (1998) provides a brief synopsis of the hazard analysis of dry fermented sausages that have now been questioned by consumers and the USDA (USDA FSIS 1995b).

Document Use | Preface | Table of Contents | References

Document Use | Preface | Table of Contents | References

2. Curing Foods

Curing is the addition to meats of some combination of salt, sugar, nitrite and/or nitrate for the purposes of preservation, flavor and color. Some publications distinguish the use of salt alone as salting, corning or salt curingand reserve the word curing for the use of salt with nitrates/nitrites. The cure ingredients can be rubbed on to the food surface, mixed into foods dry (dry curing), or dissolved in water (brine, wet, or pickle curing). In the latter processes, the food is submerged in the brine until completely covered. With large cuts of meat, brine may also be injected into the muscle. The term pickle in curing has been used to mean any brine solution or a brine cure solution that has sugar added.

2.1. Salting / Corning

Salt inhibits microbial growth by plasmolysis. In other words, water is drawn out of the microbial cell by osmosis due to the higher concentration of salt outside the cell. A cell loses water until it reaches a state first where it cannot grow and cannot survive any longer. The concentration of salt outside of a microorganism needed to inhibit growth by plasmolysis depends on the genus and species of the microorganism. The growth of some bacteria is inhibited by salt concentrations as low as 3%, e.g., Salmonella, whereas other types are able to survive in much higher salt concentrations, e.g., up to 20% salt for Staphylococcus or up to 12% salt for Listeria monocytogenes (Table 5.3.). Fortunately the growth of many undesirable organisms normally found in cured meat and poultry products is inhibited at relatively low concentrations of salt (USDA FSIS 1997a).

Salting can be accomplished by adding salt dry or in brine to meats. Dry salting, also called corning originated in Anglo-Saxon cultures. Meat was dry-cured with coarse "corns" or pellets of salt. Corned beef of Irish fame is made from a beef brisket, although any cut of meat can be corned. Salt brine curing involves the creation of brine containing salt, water and other ingredients such as sugar, erythorbate, or nitrites. Age-old tradition was to add salt to the brine until it floated an egg. Today, however, it is preferred to use a hydrometer or to carefully mix measured ingredients from a reliable recipe. Once mixed and placed into a suitable container, the food is submerged in the salt brine. Brine curing usually produces an end product that is less salty compared to dry curing. Injection of brine into the meat can also speed the curing process.

2.2. Nitrate/ Nitrite Curing

Most salt cures do not contain sufficient levels of salt to preserve meats at room temperature and Clostridium botulinum spores can survive. In the early 1800's it was realized that saltpeter (NaNO3 or KNO3) present in some impure curing salt mixtures would result in pink colored meat rather than the typical gray color attained with a plain salt cure. This nitrate/nitrite in the curing process was found to inhibit growth of Clostridium. Recent evidence indicates that they may also inhibit E. coli, Salmonella, and Campylobacter if in sufficient quantities (Condon 1999, Doyle 1999).

Several published studies indicated that N-nitrosoamines were considered carcinogenic in animals. For this reason, nitrate is prohibited in bacon and the nitrite concentration is limited in other cured meats. In other cured foods, there is insufficient scientific evidence for N-nitrosamine formation and a link to cancer (Pariza 1997).

1. For more information, please refer to the following resources:


2. Examination of Dietary Recommendations for Salt-Cured, Smoked, and Nitrite-Preserved Foods (Pariza 1997).
3. Nitrite in Meat (Epley et al.1992).
4. Safety of Cured Pork Products (Cassens 2001).

2.3. Cure Mixtures

For the home food preserver, measuring small batches of cure for nitrites or nitrates would require an analytical scale that few consumers have access to. Therefore, some manufacturers sell premixed salt and nitrate/nitrite curing mixes for easy home use. Caution is needed when using pure saltpeter instead of commercially prepared mixes, since accidental substitution of saltpeter for table salt in recipes can result in lethal toxic levels (Borchert and Cassens 1998).

Some examples of commercially prepared cures include:

2.3.1. Prague Powder #1, Insta Cure, or Modern Cure.

This cure contains sodium nitrite (6.25%) mixed with salt (93.75%). Consumers are recommended to use 1 oz. for every 25 lb. of meat or one level teaspoon of cure for 5 lb. of meat.

2.3.2. Prague Powder #2

This mix is used for dry cured meats that require long (weeks to months) cures. It contains 1 oz. of sodium nitrite and 0.64 oz. of sodium nitrate. It is recommended that this cure be combined with each 1 lb. of salt and for products that do not require cooking, smoking, or refrigeration. This cure, which contains sodium nitrate, acts like a time-release cure, slowly breaking down into sodium nitrite, then into nitric oxide. The manufacturer recommends using 1 oz. of cure for 25 lbs. of meat or one level teaspoon of cure for 5 lbs. of meat.

2.3.3. Mixes

Many individual manufacturers and commercial sausage makers produce curing mixtures, often combining sugar and spices with the salt and nitrite/nitrates. It is important that consumers follow manufacturer directions carefully.

For more information, please refer to the following products, companies, and available resources:

1. Morton Salt Meat Curing Products (Morton Salt Co. 2001). Their products include Tender Quick, Sugar Cure, and Smoke Flavored Sugar Cure.
2. Curing Products (Mandeville Co. 2001). Their products include Poultry Cure, Quick Cure, Golden Cure, Complete Cure, Maple Flavor Cure, and Myco Pickle.