CanningLow acid foods require extra care | Life

It’s canning season, so this is a good time to review canning low-acid foods, especially green beans, a food that is often misused. Low acid foods are those with a pH above 4.6. The pH of the food is important because those with a pH above 4.6 allow Clostridium botulinum to grow in canned foods and produce botulinum toxin. Meat, seafood, legumes, vegetables—including green beans, corn, carrots, and zucchini—and mixtures of these foods all have a pH above 4.6. Many other foods, such as tomatoes and white-fleshed peaches, usually have a pH above 4.6.

Because Clostridium botulinum forms spores, a resistant form of the bacteria, low-acid foods should be properly handled in a pressure vessel. Spores survive boiling water temperatures of 212 degrees Fahrenheit and can only be killed at higher temperatures, around 240 degrees Fahrenheit. These temperatures can only be reached using a pressure vessel. If low-acid food is not processed in a pressure vessel, bacteria will begin to grow after the food has cooled by producing toxins in an anaerobic environment.

Alternatively, low acid foods can be acidified with the addition of acid, which inhibits the growth of bacteria.