Use a pressure canner when preserving vegetables

By Deb Botzek-Linn,
food safety educator, University of Minnesota Extension
Safe home canned vegetables require processing in a pressure canner. This is important to know if you are planning to home can green beans, peas, carrots or other low-acid vegetables this summer.

The acidity in the food determines if fruits or vegetables are processed in a pressure canner or a boiling water bath canner to control botulism bacteria. Low-acid vegetables and meats contain too little acidity to prevent the growth of these bacteria and must be pressure canned.

Clostridium botulinum bacteria are the main reason why low-acid foods must be pressure canned to be safe. Botulism is a deadly form of food poisoning. It’s most commonly found in improperly processed home canned vegetables, such as peas, peppers, carrots, green beans and mushrooms, as well as other low-acid foods canned at home, including soups, meats, fish and poultry. Because these bacteria grow only in the absence of air, they are harmless on fresh foods.

The spores of Clostridium botulinum can only be destroyed by canning the food at a temperature of 240 degrees or above for a specific period of time. Since this temperature is above the boiling point of water, it can only be reached in a pressure canner. If canned food isn’t processed properly, spores of the bacteria aren’t killed.

Acid foods, such as fruits, pickles, sauerkraut, jams and jellies contain enough acidity to block the growth of botulism bacteria and can safely be processed in a water bath canner.

For pressure canning directions and recommended processing times visit the University of Minnesota Extension website at www.extension.umn.edu and search for “food preservation.” It is critical to use up-to-date research-tested methods when home canning.

Freezing, pickling, or drying are safe and tasty alternative methods of preserving low-acid vegetables if you do not have a pressure canner.