High-acid foods, such as most fruits, jams, pickles and tomatoes with added acid, can be processed in a boiling water bath. Low-acid foods, including vegetables, beans, meat, poultry and fish, must be pressure canned to reach 240°F, the temperature needed to destroy botulism spores. Follow a tested recipe from the USDA or National Center for Home Food Preservation, adjust for altitude, and have dial gauges tested every year.
Canning is safe when you match the method to the food’s acidity and follow a tested recipe.
Which method
| Food | Acidity | Method |
|---|---|---|
| Jams, jellies, most fruits | High | Water bath |
| Pickles and relishes | Acidified | Water bath |
| Tomatoes | Borderline | Water bath with added acid, or pressure |
| Vegetables, beans, potatoes | Low | Pressure only |
| Meat, poultry, fish, stock | Low | Pressure only |
| Soups and mixed recipes | Usually low | Pressure, tested recipe only |
Why acidity matters
Clostridium botulinum spores survive boiling. In low-acid, airless jars they can produce a deadly toxin. Pressure canners reach 240°F, which destroys the spores in the processing time a tested recipe gives.
Pressure canners
- Dial gauge: shows pressure; test it yearly for accuracy.
- Weighted gauge: rocks or jiggles at set pressures; does not need testing.
- Capacity: check how many quart and pint jars fit, and whether your stove can support it. Some glass-top stoves are not suited to heavy canners.
Altitude
Above 1,000 feet, water boils at a lower temperature. Tested recipes give longer water bath times or higher pressure for your altitude.
Tested recipes only
Use recipes from the USDA Complete Guide to Home Canning, the National Center for Home Food Preservation, extension services or canner makers that follow them. Do not invent processing times.
For shelf-stable food without jars, see freeze dryer vs dehydrator. For what to grow, see food gardens.
Browse preserving and kitchen.
Common questions
Can I water bath can green beans?
No. Green beans are a low-acid food and must be pressure canned. Water bath canning does not get hot enough to destroy botulism spores.
Do tomatoes need a pressure canner?
Tomatoes can be water bath canned only with added lemon juice or citric acid as specified in a tested recipe. They can also be pressure canned.
Can I use an electric pressure cooker for canning?
The National Center for Home Food Preservation does not recommend most electric multicookers for pressure canning. Use a canner designed and tested for it.
How often should a dial gauge be tested?
Every year. Many county extension offices test gauges. Weighted-gauge canners do not need testing.