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
- As fill weight of jars increases, the f(h) value and required
processing time will increase.
- 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
- Wash, peel and trim jicama; dice.
- Place pickling spice and cinnamon on a double-layer of 100%
cotton cheesecloth. Bring corners together and tie with a clean
string.
- 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.
- 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.
Table 1. Determination of Cold Spot Location
| Thermocouple
Height in Pint Jar |
Average
f(h) Value |
Range |
Standard Deviation
|
| |
n = 12 |
|
|
| Center |
29.5A1 |
24.6 - 34.1 |
2.9 |
| ½" Below Center |
37.3B |
32.3 - 41.4 |
2.9 |
| 1" Below Center |
35.7B |
30.7 - 40.2 |
2.9 |
| 1½" Below Center2 |
40.2B |
37.2 - 44.0 |
1.9 |
| 2" Below Center |
37.5B |
34.4 - 43.6 |
2.8 |
1 Values with different letters in the
same column are significantly different at p<.001.
2 Location of cold spot, as determined by largest individual
f(h) value (worst-case scenario). |
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.
Table 2. Thermal Characteristics of Jars Processed
by Three Methods
| |
Procedures |
Standard
n=15 |
Overfill
n=12 |
Low Fill
Temperature
n=15 |
| Total Fill Weight (Solids + Liquids) |
454 g |
490 g |
454 g |
| Solids Fill Weight |
354 g |
472 g |
354 g |
| |
°C |
°C |
°C |
| Canner Initial Temperature (n=3)1 |
82.0 ± 0.6 |
82.7 ± 0.4 |
82.2 ± 0.4 |
| Jar Initial Temperature |
69.7 ± 2.0 |
73.2 ± 4.2 |
64.5 ± 2.0 |
| Jar Temperature at Start of Boiling |
80.4 ± 2.0 |
72.4 ± 2.5 |
79.5 ± 2.0 |
| Temperature change during come-up time |
+ 10.7 |
- 0.8 |
+15.0 |
| Jar Temperature after 35 Minutes of Boiling2 |
96.9 ± 0.5 |
91.3 ± 0.8 |
97.0 ± 0.3 |
| Maximum temperature change during process |
+ 27.2 |
+ 18.1 |
+ 32.5 |
| |
Minutes |
Minutes |
Minutes |
| Maximum Time to Reach 90.5°C3 |
14 |
344 |
16 |
| Recommended Process time (time at boiling)5 |
15 |
35 |
20 |
1 Heat penetration data for 12-15 jars were collected from 3 different canner loads.
2 Heat penetration data were collected for 35 mins once the canner was brought to boiling.
3 Values taken from worst-case individual jars; not averages.
4 One jar did not reach 90.5°C until two minutes into the cooling periood; its maximum temperature at the end of 35 minutes of boiling was 89.4°C.
5 Time needed to heat the product to 90.5° for one minute.
|
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.
Table 3. Effect of Fill Weight and Fill Temperature
on Heat Penetration.
| |
Procedures
|
Standard
n=15 |
Overfill
n=12 |
Low Fill Temperature
n=15 |
| Total Fill Weight (Solids + Liquid) |
454g |
490g |
454g |
| Solids Fill Weight |
354g |
472g |
354g |
| |
|
|
|
| Jar Initial Temerature (°C) |
69.7 ± 2.0A1 |
73.2 ± 4.2A |
64.5 ± 2.0B |
| f(h) |
33.5 ± 2.5A |
61.1 ± 2.0B |
34.6 ± 2.4A |
| Average Minutes to Reach 90.5°C at Boiling
2 |
11.3 ± 2.3A |
34.8 ± 2.4B3 |
11.3 ± 2.4A |
1 Values with different letters in the same
row indicate a significant difference at p<.001.
2Time after water in canner returned to boiling. This comparison
of averages is for statistical purposes; in practice,
the process time would be determined by the slowest heating
individual jar.
3One jar did not reach 90.5°C until two minutes into the
cooling period; its maximum temperature at the end of
35 minutes of boiling was 89.4°C.
|
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
- 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.
- 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.
- 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.
- 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.
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