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Food Safety & Preservation

Latest food safety and preservation information from Cook County Extension
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The Rules of Home Canning

Posted by Ron Wolford -

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 by the US Department of Agriculture and disseminated to the public by State Extension Offices across the nation. While some of the old recipes and methods are still being used today, they may not be safe, according to Drusilla Banks, University of Illinois Extension Specialist, Food Science and Nutrition Programming,

With increased interest in locally grown foods, farmers markets, and home gardening, many novices are freezing and canning their summer's bounty using old outdated recipes and methods. The science of preserving food at home is not difficult to understand, but there are strict rules to follow in order to produce a safe product. Using outdated methods can be deadly.

The canning methods used by your grandma may have been considered safe at that time, but not today. There are no safe shortcuts in home food preservation. Recipes and methods in magazines, on TV cooking shows, and in old cookbooks may not be safe. Always start with reliable and safe recipes and do not alter what is written.

"Every year I get calls on how long to 'water bath' green beans," Banks 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, Banks says.

Even tomatoes are iffy because the acidity level of tomatoes varies with variety, growing conditions and condition of the vines, according. Because of these variances, all tomatoes—no matter what type—need to be acidified before water bath 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. Pressure saucepans should be used for cooking food not canning.

Fruits, pickles, acidified tomato products, jams and jellies must 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, Banks says, this method was outlawed in 1946. The boiling water bath canner adds extra sterilization protection to the food being processed preventing mold growth and the growth of other illness causing pathogens.

Banks recommends that individuals wanting to preserve food at home should purchase a reliable canning cookbook. The University of Georgia Extension conducts USDA sponsored research on the latest safe home canning methods. U of G has published an excellent book So Easy to Preserve 5th Edition that is available in many local Extension offices and also may be ordered online. The cost of the book is $18. You can order the book and download free recipes and information from their website the National Center for Home Food Preservation at

The USDA Complete Guide to Home Canning may also be available from county Extension offices, while supplies last or you can order it online from several sources. Look for the PDF version available online for a limited time at the National Center for Home Food Preservation website.

If you have questions about home food preservation, contact your local University of Illinois Extension office. If you have home preservation and canning questions, the University of Illinois Extension Chicago has an Ask a Master Food Preserver blog which is at

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.

Please be safe when canning foods for you and your family! Knowledge and recommendations have changed and improved over time with new scientific developments. You should use up-to-date recommendations and methods and not just rely on practices of past generations, friends or even family members.

Drusilla M. Banks, MS

Extension Specialist,

Food Science and Nutrition Programming

University of Illinois Extension at Wright College

4300 N. Narragansett Ave, Suite L-254

Chicago, IL 60634

Phone: (773) 481-8634 Fax (773) 481-8185


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