Burning Issue: Canning in Pressure Cookers
What are the process times for canning in my pressure cooker?
USDA does not have recommended processes for canning in a small pressure cooker. The recommendation for using USDA pressure processes for low-acid foods is to use a canner that holds at least four (4) quart-size jars standing upright on the rack, with the lid in place. The research for USDA pressure processes for vegetable and meat products was conducted in pressure canners that are most similar to today's 16-quart or larger pressure canners.
Pressure cookers have less metal, are smaller in diameter, and will use less water than pressure canners. The result is that the time it takes a canner to come up to processing pressure (that is, the come-up time) and the time it takes the canner to cool naturally down to 0 pounds pressure at the end of the process (known as the cool-down time) will be less than for the standard pressure canner. The come-up and cool-down times are part of the total processing heat that was used to establish USDA process times for low-acid foods. If the heat from the come-up and cool-down periods is reduced because these times are shortened, then the heat from the process time at pressure alone may not be enough to destroy targeted microorganisms for safety. That is, the food may end up underprocessed. Underprocessed low-acid canned foods are unsafe and can result in foodborne illness, including botulism poisoning, if consumed.
During earlier years of canning research, pressure saucepans were considered an alternative for home canning and it was thought that adding 10 minutes to the process times for standard canners would keep food safe. That proved not to be the case for a general, across-the-board recommendation, as there are several sizes of pressure saucepans and they were not all adequately tested. In addition, the way heat transfers (penetrates) through food during the process is affected partly by the composition of the food and not all foods and styles of preparation were tested. Later research published in journals has not resulted in an absolute recommendation either. Therefore, in the late 1980s the USDA published its recommendation to not use pressure saucepans (small cookers) for home canning.
Some manufacturers may offer process directions for smaller pressure cookers. Consumers using this equipment will need to discuss processing recommendations with those manufacturers; the USDA and National Center for Home Food Preservation recommendation is to not use them for canning with our processes.
To be considered a pressure canner for USDA processes, the canner must be able to hold at least four quart-size jars, standing upright on the canner rack, with the lid in place. It is also important to realize the canner should have a way to follow recommended venting procedures to remove air from inside the canner before it is pressurized, and to indicate that the canner remains at least at the target pressure throughout the entire process time. (Also see: Using Pressure Canners)
We cannot convert processes intended for use with regular pressure canners to ensure safety when canning in other types of equipment.
National Center for Home Food Preservation
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