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General Canning Information

For Safety's Sake

Pressure canning is the only recommended method for canning meat, poultry, seafood, and vege­tables. The bacterium Clostridium botulinum is destroyed in low-acid foods when they are processed at the correct time and pressure in pressure canners. Using boiling water canners for these foods poses a real risk of botulism poisoning.

If Clostridium botulinum bacteria survive and grow inside a sealed jar of food, they can pro­duce a poisonous toxin. Even a taste of food containing this toxin can be fatal. Boiling food 10 minutes at altitudes below 1,000 feet altitude should destroy this poison when it is present. For altitudes at and above 1,000 feet, add 1 additional minute per 1,000 feet additional elevation. Boiling means that you are able to see the liquid in the food actively forming large foamy bubbles that break all over the surface. Note that as of July 2013 the Centers for Disease Control and Prevention (CDC) recommendation is to discard any home canned food that might contain botulism toxin. (http://www.cdc.gov/features/homecanning/)

Caution: To prevent the risk of botulism, low-acid and tomato foods not canned according to the recommendations in the USDA Complete Guide to Home Canning (2009rev) or according to other USDA-endorsed recom­mendations should be boiled as above, in a saucepan before consuming, even if you detect no signs of spoilage.

This is not intended to serve as a recommendation for consuming foods known to be significantly underprocessed according to current standards and recommended methods. It is not a guarantee that all possible defects and hazards with other methods can be overcome by this boiling process.
The recommendation is to only can low-acid foods and tomatoes and tomato products according to the procedures in the USDA Complete Guide to Home Canning (2009) (which are the ones found in the How Do I?... menus on this website.)  There are other pickles, relishes and salsas containing tomatoes that are acceptable and those we can support at the National Center are on our website.

All low-acid foods canned according to the approved recommendations may be eaten without boiling them when you are sure of all the following:

  • Food was processed in a pressure canner operated according to the procedures in the USDA guidelines.
  • The gauge of the pressure canner was accurate.
  • Up-to-date researched process times and pressures were used for the size of jar, style of pack, and kind of food being canned.
  • The process time and pressure recommended for sterilizing the food at your altitude was followed.
  • The jar lid is firmly sealed and indicates a vacuum seal is present.
  • Nothing has leaked from jar.
  • No liquid spurts out when jar is opened.
  • No unnatural or “off” odors can be detected. No mold is present.


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

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