Preventing Botulism in Home-Canned Food

In brief

• You can prevent botulism when preserving food at home.
• Always follow safe canning instructions and use the right equipment.
• When in doubt, throw it out. Never taste food to check whether it is safe.

A pressure canner beside jars of home-canned food. Image from CDC's page.

Why it matters

You cannot see, smell or taste the toxin that causes botulism, and even a small taste of food containing it can be deadly. Home foods that were improperly canned, preserved or fermented are common sources of foodborne botulism. Store-bought food can be contaminated too, though that is uncommon.

Follow tested instructions

The best prevention is to follow the instructions for safe home canning in the USDA Complete Guide to Home Canning.

• Use only recipes and cookbooks that follow the USDA guide's steps.
• Do not use other recipes, even ones from a trusted friend or relative.

Low-acid foods need a pressure canner

Take particular care with low-acid foods — those with a pH above 4.6: all fresh vegetables, figs, meat, poultry, fish, seafood, and some tomatoes. They are the most common sources of botulism from home canning, and home-canned vegetables are the most common cause of botulism outbreaks in the United States.

Pressure canning is the only recommended method for low-acid foods.

• Do not use a boiling-water canner for them — it will not protect against botulism.
• Do not use an electric multi-cooker, even one with a "canning" or "steam canning" button. Why.

When pressure canning:

• Use a recommended canner that holds at least four 1-quart jars upright on its rack.
• Make sure the canner's gauge is accurate. Many county extension offices check gauges; the manufacturer can suggest other options.
• Clean the lid gasket and other parts as the manufacturer directs.
• Vent the canner before pressurizing it, and follow the recommended cooling steps.
• If your recipe is old, use current processing times and pressures, taking account of the kind of food, the jar size and how the food is packed. Pay special attention to processing times for low-acid foods.

Store it safely

• Can only as much food as you will use in 1 year, unless directions for a particular food say otherwise.
• Label and date the jars.
• Keep them somewhere clean, cool and dark — for best quality between 50°F and 70°F.
• For safety, never above 95°F, and not near hot pipes, a range or a furnace, in an uninsulated attic, or in direct sunlight.

Boil before eating

High heat destroys the toxin. Boil these in a saucepan before eating them:

• home-canned tomatoes, and foods containing them;
• all low-acid home-canned foods;
• all home-fermented Alaska Native foods — the usual source of botulism in Alaska.

Below 1,000 feet of altitude, boil for 10 minutes; add 1 minute for every additional 1,000 feet.

Throw it out

Do not eat food if you do not know whether safe canning guidelines were followed. Throw out any home-canned or store-bought food if:

• the container is leaking, bulging or swollen;
• it looks damaged, cracked or abnormal;
• it spurts liquid or foam when opened;
• the food is discolored, moldy or smells bad.

More ways to prevent botulism

• Refrigerate canned or pickled foods after opening.
• Refrigerate homemade oils made with garlic or herbs, and throw away what is left after 4 days.
• If you bake potatoes in aluminum foil, keep them at 140°F or hotter until served, or refrigerate them with the foil loosened so air gets in.

For more, see the National Center for Home Food Preservation and your state's extension service.

Sources

Based on "Botulism and Home-Canned Foods," Centers for Disease Control and Prevention; a work of the United States government in the public domain.