Home Canning and Botulism
What You Need to Know
- You cannot see, smell, or taste the toxin that causes botulism, but even a small taste of food containing the toxin can be deadly.
- Follow these steps to prevent botulism:
- Always use proper canning techniques.
- If you have any doubt about whether food was canned properly, throw it out.
- Throw out any canned food with signs of contamination. Never taste food to see if it’s safe.
- Botulism is an emergency. Seek medical help immediately if you or someone you know has symptoms.
Home canning is an excellent way to preserve garden produce and share it with family and friends. But it can be risky—even deadly—if not done correctly and safely. Home-canned vegetables are the most common cause of botulism outbreaks in the United States. Learn how you can preserve vegetables—as well as fruits, meats, seafood, and more—correctly and safely.
What Is Botulism?
Botulism is a rare but serious illness caused by a toxin that attacks the body’s nerves. It can cause difficulty breathing, muscle paralysis, and even death. The toxin is made most often by Clostridium botulinum bacteria. Improperly canned, preserved, or fermented foods can provide the right conditions for the bacteria to make the toxin.
You cannot see, smell, or taste the toxin, but taking even a small taste of food containing it can be deadly.
Botulism is a medical emergency. If you or someone you know has symptoms of botulism, contact your doctor or go to the emergency room immediately.
Prevent Botulism From Home-Canned Foods
You can protect yourself, your family, and others by following these tips.
1. Use proper canning techniques.
The best way to prevent foodborne botulism is by carefully following instructions for safe home canning from the USDA Complete Guide to Home Canning. Only use recipes and cookbooks that follow the steps in the USDA guide. Don’t use other recipes, even if you got them from a trusted friend or family member.
2. Use the right equipment for the kind of food you are canning.
Low-acid foods are the most common sources of botulism linked to home canning. These foods have a pH level greater than 4.6. Low-acid foods include most vegetables (including asparagus, green beans, beets, corn, and potatoes), some fruits (including some tomatoes and figs), milk, all meats, fish, and other seafood.
Pressure canning is the only recommended method for canning low-acid foods.
- Do not use a boiling water canner for low-acid foods because it will not protect against botulism.
- Do not use an electric, multi-cooker appliance, even if it has a “canning” or “steam canning” button on the front panel. Learn more.
When pressure canning, keep the following things in mind.
- Use a recommended pressure canner that holds at least four one-quart jars sitting upright on the rack.
- Be sure the gauge of the pressure canner is accurate. Many county extension offices will check gauges. Contact the pressure canner manufacturer for other options.
- Clean lid gaskets and other parts according to the manufacturer’s directions.
- Vent the pressure canner before pressurizing and follow recommended cooling steps.
- Use up-to-date processing times and pressures for the kind of food, the size of jar, and the method of packing food in the jar. Pay special attention to processing times for low-acid foods.
Review USDA’s Complete Guide to Home Canning [PDF – 40 pages] for more information on pressure canning.
3. When in doubt, throw it out!
If you have any doubt whether safe canning guidelines have been followed, do not eat the food.
Home-canned and store-bought food might be contaminated with toxins or harmful germs if:
- the container is leaking, bulging, or swollen;
- the container looks damaged, cracked, or abnormal;
- the container spurts liquid or foam when opened; or
- the food is discolored, moldy, or smells bad.
More Ways to Prevent Botulism
- Refrigerate any canned or pickled foods after you open them.
- Always use traditional methods when preparing Alaska Native foods.
- Refrigerate homemade oils infused with garlic or herbs and throw away any unused oils after 4 days.
- If you bake potatoes wrapped in aluminum foil, keep them hot (at temperatures hotter than 140°F) until they are served or refrigerate them with the foil loosened so they get air.
- National Center for Home Food Preservation
- State and County Extension Services (click on your state or scroll down for a list of all services)
- CDC’s Botulism Website