Home Canning Safety: The Botulism Rules You Can't Break

Home canning turns a harvest into a pantry that lasts through winter, and a collapse. But canned food done wrong can grow Clostridium botulinum, whose toxin attacks the nerves and can cause paralysis and death. Home-canned vegetables are the most common cause of botulism outbreaks in the U.S. These rules are not optional.

Rule 1: low-acid foods need a pressure canner

Low-acid foods have a pH above 4.6: all fresh vegetables, figs, meat, poultry, fish, seafood, and some tomatoes.

• Pressure canning is the only recommended method for low-acid foods.
• A boiling-water canner will not protect against botulism for these foods: boiling water can’t get hot enough to kill the spores.
• Don’t use electric multi-cookers for canning, even ones with a “canning” button.

The pressure canner should hold at least four 1-quart jars upright, and a dial gauge should be checked for accuracy.

Rule 2: follow tested times exactly

Use only recipes and processing times that follow the USDA Complete Guide to Home Canning, not family recipes or old books. The USDA canning bulletins in our library explain the principles well, but their times are from the 1960s and 70s and have since been revised.

Rule 3: when in doubt, throw it out

Throw away, without tasting, any jar or can that is:

• leaking, bulging or swollen;
• damaged or cracked;
• spurting liquid or foam when opened;
• discolored, moldy or bad-smelling.

Never taste food to check whether it’s safe. If you don’t know whether safe canning steps were followed, don’t eat it.

Extra margin

CDC advises that if you’re unsure about home-canned low-acid food, boil it for 10 minutes before eating (add 1 minute for every 1,000 feet above 1,000 feet of elevation) to destroy the toxin.

Once opened, canned and pickled foods go in the refrigerator. See also the food danger zone.