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Pressure Canning

Every year we get the following question at the Home & Garden Information Center:

“I canned my green beans in a water bath canner. Are they safe?”

And when we say NO, we hear:

“But my mother and grandmother always did it that way, and they survived.”  

It is not safe to process green beans and other vegetables in a water bath canner. Why? Because of Clostridium botulism. Botulism is a serious food poisoning caused by a toxin (poison) produced by the bacteria, Clostridium botulinum. C. botulinum and its spores are everywhere in nature and present in soil and water worldwide. The bacteria and spores are actually harmless until they are introduced to a very specific environment. C. botulinum spores thrive in an atmosphere that is low acid, low oxygen, at ambient temperatures (think room temperature), and moist. Give them those conditions for a couple of hours, and they will start to produce a highly toxic nerve poison that leads to extreme illness or even death. Turns out, this is the exact environment created when you home can low acid foods.

Only a pressure canner can heat low-acid foods to the temperature (240 °F to 250 °F) required to destroy the spores of C. botulinum. That is why low-acid foods, such as green beans, vegetables, meats, poultry, and fish (pH above 4.6) must be pressure canned.

A simple dial gauge pressure canner will safely process green beans and other low acid foods.

A simple dial gauge pressure canner will safely process green beans and other low acid foods.

So, know this. Pressure canning is the only safe method of processing low-acid foods. You must follow a tested, proven recipe to ensure a safe final product. Reliable sources for tested recipes include the Clemson Home & Garden Information Center (hgic.clemson.edu), the University of Georgia’s National Center for Home Food Processing and Preservation (nchfp.uga.edu), the Ball Blue Book Guide to Preserving, the Ball Complete Book of Home Preserving, and the Jarden Foods (Ball) website (freshpreserving.com). Avoid on-line recipes and old untested recipes.

And, as for those friends and family members of past generations, who are passing down out-of-date canning methods. they really did get lucky. Research over the past 50 years, proves that there is a real risk of botulism poisoning when low acid foods are not pressure canned.

Canning is hard work, takes a lot of time, and isn’t especially cheap. Do you really want to be wondering if those beautiful jars of food that you worked so hard to create are actually vessels of sickness and death? That’s a pretty dramatic statement, but really?

 

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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