Home Canning and Botulism

Home canning is an excellent way to preserve garden produce and share it with family and friends. But it can be risky—or even deadly—if not done correctly and safely.

It’s summertime and time to harvest the delicious produce you’ve been growing. You may be thinking about home canning as a way to preserve your garden goodies. But beware! If home canning is not done the proper way, your canned vegetables and fruits could cause botulism.

What is botulism?

Botulism is a rare but potentially deadly illness caused by a poison most commonly produced by a germ called Clostridium botulinum. The germ is found in soil and can survive, grow, and produce a toxin in certain conditions, such as when food is improperly canned. The toxin can affect your nerves, paralyze you, and even cause death.

You cannot see, smell, or taste botulinum toxin—but taking even a small taste of food containing this toxin can be deadly.

What’s a low-acid food?

Low-acid foods have a pH level greater than 4.6, which means they are not acidic enough to prevent the growth of botulinum bacteria. Examples are:

Asparagus
Green beans
Beets
Corn
Potatoes
Some tomatoes *
Figs
All meats
Fish and seafood

*Tomatoes require added acid – lemon juice or citric acid – for safe home canning.

What are the symptoms of botulism?

Botulism is a medical emergency. If you or someone you know has symptoms of foodborne botulism, see your doctor or go to the emergency room immediately.

Symptoms may include the following:

Double vision
Blurred vision
Drooping eyelids
Slurred speech
Difficulty swallowing
A thick-feeling tongue
Dry mouth
Muscle weakness

How can I keep myself and others safe when it comes to home-canned foods?

Many cases of foodborne botulism have happened after people ate home-canned, preserved, or fermented foods that were contaminated with toxin. The foods became contaminated because they were not canned (processed) correctly.

You can take steps to protect yourself, your family, and others when it comes to home-canned foods 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 in the USDA Complete Guide to Home Canning . Do not follow recipes and cookbooks that do not follow the steps in the USDA guide, even if you got these items from a trusted friend or family member.

You can learn more about proper home canning from these resources:

The National Center for Home Food Preservation
State and county extension services (click on your state or scroll down for a list of all services)

2. Use the right equipment for the kind of foods that you are canning.

Pressure canning is the only recommended method for canning low-acid foods. Foods with low acid content are the most common sources of home-canning related botulism cases. Low-acids foods include almost every vegetable, some fruits, milk, all meats, fish, and seafood. See box to the right for examples. Do not use boiling water canners for low-acid foods because they will not protect against botulism.

Always use a properly sized pressure canner that meets USDA recommendations for pressure canning[3.61 MB] when canning low-acid foods. Contact your state or county extension service to find out if your pressure canner meets USDA recommendations.

Make your home-canned vegetables, meats safe

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. Gauges may be checked at many county Cooperative Extension offices or 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 process times and pressures for the kind of food, the size of jar, and the method of packing food in the jar.

Learn more about canners and processing time >[3.61 MB]

3. When in doubt, throw it out!

If there is any doubt if safe canning guidelines have been followed, do not eat the food. Home-canned and store-bought food might be contaminated with toxin or other 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;
the food is discolored, moldy, or smells bad.

If the container or the food inside has any signs of contamination, throw it out! If any of the food spills, wipe up the spill using a solution of 1/4 cup bleach for each 2 cups of water.

Never taste food to determine if it is safe. Do not taste or eat food that is discolored, moldy, or smells bad. Do not taste or eat food from cans that are leaking, have bulges or are swollen, or look damaged, cracked, or abnormal. Do not taste or eat food from a can that spurted liquid or foam when it was opened. Learn more >