Low-Acid Foods
Pressure Canning
Foods with a pH above 4.6 are low-acid foods.
Is my food low-acid? See this chart from FDA.
Low-acid foods allow spores of Botulinum species to grow in an environment free of oxygen like sealed jars. As these bacteria grow they produce a deadly toxin that leads to botulism. (Learn more about botulism here.) In order to safely can low-acid foods we need to use pressure canners to achieve the necessary temperature to kill spores. Pressure canners may also be used to preserve some high-acid foods as well, but ALL LOW-ACID FOODS MUST BE PRESSURE CANNED.
While botulism is itself scary, some home cooks are more afraid of pressure canners than the deadly disease. Today's pressure canners are very safe, and their use is not difficult.
At most locations in Inyo and Mono counties, you will need to adjust canning recipes to increase pressure due to elevation. All reputable recipes include this information. If you are using a dial-gauge Presto canner, we can inspect the dial to ensure your canner's pressure is correct.
With practice canning a few tested recipes you will gain confidence in your ability to pressure can!
About Pressure Canners
Currently there are 3 main manufacturers of pressure canners in the North American market: Mirro, Presto, and All-American. There are a few other makes as well. In order for a pressure canner to safely process food, it must be large enough to process at least 4 quart jars at once. If it is smaller, then the heat transfer and cool down time may be inadequate.
Please contact our program at immg@ucanr.edu if you have questions about your canner or its use.
Are Instant-Pots and other electric multi-cookers OK?
NO. Even if the instructions include directions for pressure canning, we do not recommend their use as canners at this time. Read about why here.
What about using pressure cookers for canning?
Recommendations for canning are developed for pressure canners, not cookers. There are differences between the design and the amount of water used in each canner that may not sufficiently process food. You should only use pressure cookers for cooking.
How do I can on a flat-top glass electric stove?
Glass top stoves are a real challenge to a home canner. In order for a canner to be used on a glass-top stove 3 criteria must be met:
- It cannot be too heavy
- It must have a flat bottom
- It cannot be more than about 2 inches wider than the burner circle.
Induction stoves must use a ferrous metal container as well.
Most manufacturers have an information page about their stoves with approved canners. Generally, it appears most current steam canners for high-acid foods and the smaller Presto canner are suitable for many stoves BUT CONSULT YOUR MANUFACTURER BEFORE USING.
In our experience, electric ranges are hard to regulate pressure on canners. A better option may be to use butane burners. Another excellent option is to use a portable camp stove. Propane or white-gas versions of camp stoves must be used outdoors only,and all portable stoves require good ventilation. Single-burner stoves that use a large propane tank, often used for frying turkeys, are too powerful.
Here is a page with information on glass-top stoves.
Where can I get recipes for safely canning with pressure canners?
These sites have reputable information about home pressure canning: