The Dangers of Water Bath Canning Vegetables

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Many people often inaccurately refer to the boiling water bath method of canning as the “old fashioned way” or “the way my grandmother did it.” While water bath canning is safe and preferred for high acid products, like jams, jellies, pickles, and fruit, research has made the risks and dangers of using this method to can low acid products, such as vegetables and meats, very evident.

The pathogen of concern when canning is Clostridium botulinum, which could cause botulism- a potentially deadly form of food poisoning. These spore forming bacteria can survive harmlessly in soil and water and are very prevalent on the surface of most fresh food surfaces. As an anaerobic bacteria, Clostridium botulinum spores only become dangerous in environments with an absence of oxygen, making them harmless on fresh food surfaces.

In certain conditions, C. botulinum spores can produce vegetative cells that rapidly multiply and produce a deadly neurotoxin within 3 to 4 days of growth. Ideal conditions for C. botulinum growth consist of: a moist, low acid food, a temperature between 40℉ and 120℉, and less than 2 percent oxygen.

Whether food should be processed in a pressure canner or a boiling water bath canner depends on the acidity of the food. Because of the acidity of high acid foods like jams, jellies, pickles, and fruit, the boiling water bath canning method is sufficient to block the growth of C. botulinum or destroy them more rapidly when heated. Foods with a pH below 4.6 are considered high acid and suitable for water bath processing.

Low acid foods have a pH higher than 4.6 and are not acidic enough to prevent the growth of these bacteria. Clostridium botulinum spores are very hard to destroy at boiling water temperatures. Therefore, all low acid foods should be processed at a temperature of 240℉ to 250℉. This is attainable with pressure canners operated at between 10 and 15 pounds per square inch and using recommended, research-based processing times. Following these guidelines will ensure destruction of the largest expected number of heat resistant microorganisms in home canned food products. If canned goods are properly sterilized and the lids seal after processing, they should be free from spoilage and safe to consume.

Is the safety of family and friends worth compromising for a fear of using a pressure canner, upholding family tradition, or avoiding the monetary investment in proper equipment? There is no way to detect botulism presence in home canned foods once processed. On average, there are about 145 cases of botulism reported each year in the United States, 15 percent of which are food borne. Yes it’s rare, but it’s also deadly. It kills by causing paralysis, eventually paralyzing organs that control breathing. It’s like the lottery that you definitely don’t want to win.

Take this information into consideration when making the decision about how to process your home canned food. Following proper guidelines can ensure confidence in the safety of the product and eliminate any worry of the presence of botulism.

N.C. Cooperative Extension, Burke County Center can offer trusted, tested canning recipes as well as research-based canning methodology. For questions about recipes, canning technique, or to get a canner gauge tested, contact Emily Troutman at emily_troutman@ncsu.edu or 828-764-9480.

Written By

Photo of Emily TroutmanEmily TroutmanExtension Agent, Family and Consumer Sciences (828) 764-9480 emily_troutman@ncsu.eduBurke County, North Carolina
Posted on Jul 13, 2017
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