The Rules of Canning - U of I Extension

News Release

The Rules of Canning

This article was originally published on July 4, 2010 and expired on August 25, 2010. It is provided here for archival purposes and may contain dated information.

If home food preservation is one of the activities on your summer agenda, University of Illinois Extension has some advice for you: know what type of process the food you are preserving requires, or you may serve up some unexpected foodborne bacteria next winter.

Research on home food preservation has been conducted since the early 1900's, and while some of those recipes and methods are still being used today, they may not be safe, according to Shirley Camp, University of Illinois Extension nutrition and wellness educator.

"Every year I get calls on how long to 'water bath' green beans," Camp says, "and since green beans are a low acid food, they MUST be processed in a pressure canner or frozen." The rule is that all foods with a pH of 4.6 or above must be processed in a pressure canner, Camp says.

Even tomatoes are iffy because the acidity level of tomatoes varies with variety, growing conditions and condition of the vines, according to Camp. Because of the variance, all tomatoes—no matter what type—need to be acidified for canning which means that 1 tablespoon of bottled lemon juice or 1/4 teaspoon of citric acid must be added to each pint of tomatoes. For quarts, use 2 tablespoons of lemon juice or 1/2 teaspoon of citric acid.

Vinegar can be used at the rate of 4 tablespoons per quart or 2 tablespoons per pint, but the vinegar can cause undesirable flavor changes. No matter what you use, you should not use tomatoes that are from diseased, dying or dead vines. However, those tomatoes may still be frozen safely.

All vegetables, vegetable mixtures and meats are low acid foods and must be processed in a pressure canner. The canner should be large enough to hold 7 quart jars, so small "pressure saucepans" should not be used.

Fruits, pickles, acidified tomato products, jams and jellies should be processed in a boiling water bath canner. Gone are the days of filling the jar with hot product and letting it seal on the counter, Camp says. The boiling water bath canner adds extra sterilization protection to the food being processed.

Camp recommends that individuals wanting to preserve food at home should purchase a reliable canning cookbook. The University of Georgia Extension has an excellent book So Easy to Preserve that is available in many local Extension offices and also may be ordered online. The cost of the book is $18. The USDA Guide to Home Canning may also be available from Extension offices, or you can find it online.

If you have questions about home food preservation, contact your local University of Illinois Extension office at 217-942-6996.

University of Illinois Extension provides equal opportunities in programs and employment. Extension programs and materials are research based and strive to meet the needs of people locally. If you need a reasonable accommodation to participate in this program, contact Rick Keim at 217/942-6996.

Source: Shirley Camp, MS RD, Extension Educator, Nutrition and Wellness (serving West Central Illinois and surrounding counties),

Pull date: August 25, 2010