New to Canning? How to Avoid Botulism

October 30, 2020

The COVID-19 pandemic has sparked a renewed interest in canning as Americans spend more time at home and make the most of their gardening season. After all, “victory gardens” rose in popularity this past spring and summer as people sought to be more self-sufficient during quarantines and lockdown periods. Canning is a wonderful way to preserve your garden labors for cozy winter meals, but it’s critical to take steps to prevent a dangerous byproduct of improperly canned foods: botulism.

What is botulism?

Botulism is a rare but potentially deadly illness caused by a toxin produced by certain germs, most notably the bacteria Clostridium botulinum. Foods that have been improperly canned, preserved or fermented are among the most commons sources of this toxin, which affects the nervous system.

Low-acid foods are more likely to contain this poison when improperly preserved. Some examples are:

Asparagus
Beets
Corn
Green beans
Mushrooms
Potatoes
Spinach
Some tomatoes
Meats
Fish and seafood

You cannot see, smell or taste the toxin, making prevention essential.

While foodborne botulism is not common, it can be fatal if it is not caught early and treated effectively.

What are the symptoms of botulism?

Early symptoms often include nausea or stomach ache, sometimes with constipation. Symptoms typically appear 12 to 36 hours after exposure, but can begin as early as 6 hours after or as long as 10 days later.

The effects on the nervous system usually begin in the head and face. Symptoms can include:

Blurred vision
Drooping eyelids
Dry mouth
Trouble swallowing and speaking

The illness can go on to cause muscle weakness, including in your arms and legs and in the muscles used to breathe, making breathing difficult.

How can I prevent botulism?

The best way to prevent foodborne botulism is by carefully following the instructions in the U.S. Department of Agriculture (USDA) Complete Guide to Home Canning. We recommend taking a canning or food preservation course with your local university extension, as well.

When canning low-acid foods, it is important to use a pressure canner, according to the Centers for Disease Control and Prevention (CDC). Do not use an electric, multicooker appliance, even if it has a canning button. It is unclear if these are effective in preventing botulism. Carefully follow the processing times given in the USDA guide.

If you have already canned your summer or fall produce, or perhaps were given a mason jar of preserved veggies by a generous friend or neighbor, pay close attention when you are ready to open the containers. Throw out any canned food —whether it’s store bought or home-canned—if it is leaking or bulging or if it looks damaged or cracked. Throw out the food if the container spurts liquid or foam when you open it or if the food is discolored or smells bad.

Store any opened canned or pickled foods in the refrigerator.

The CDC recommends caution when you are throwing out possibly contaminated food. Use rubber or latex gloves before you handle it. Put the food in a sealable plastic bag, then wrap another plastic bag around it and tape it shut. Place the bags in a trash receptacle outside the house. Use a bleach solution to wipe up any spills. Wash your hands with soap and water for at least two minutes afterward.

What should I do if I think I have botulism?

If you are showing signs of botulism, contact the poison center right away. The poison center’s experts can tell you what steps you need to take immediately and direct you to the best place for further care. Call the poison center at 1-800-222-1222, chat online at nnepc.org or text POISON to 85511.

Gayle Finkelstein, MS, is Poison Prevention Educator with the Northern New England Poison Center.