Using Pressure Canners
THE UNIVERSITY OF GEORGIA
College of Family and Consumer Sciences
in cooperation with the College of Agricultural and Environmental Sciences
Pressure canners for use in the home were extensively redesigned beginning in the 1970's. Models made before the 1970's were heavy-walled kettles with clamp-on or turn-on lids. They were fitted with a dial gauge, a vent pipe in the form of a petcock or covered with a counterweight, and a safety fuse. Most modern pressure canners are lightweight, thin-walled kettles; most have turn-on lids fitted with gaskets. At least one style is still made with heavy cast aluminum, has screw-down knobs around the canner and does not have a gasket, however.
Modern pressure canners have removable racks, an automatic vent/cover lock, a vent pipe (steam vent), and a safety fuse. Use only canners that have the Underwriter’s Laboratory (UL) approval to ensure their safety.
Today’s pressure canner may have a dial gauge for indicating the pressure or a weighted gauge, for indicating and regulating the pressure. Weighted gauges are usually designed to "jiggle" several times a minute or to keep rocking gently when they are maintaining the correct pressure. Read your manufacturer’s directions to know how a particular weighted gauge should rock or jiggle to indicate that the proper pressure is reached and then maintained during processing. Dial gauge canners will usually have a counterweight or pressure regulator for sealing off the open vent pipe to pressurize the canner. This weight should not be confused with a weighted gauge and will not jiggle or rock as described for a weighted gauge canner. Pressure readings on a dial gauge canner are only registered on the dial and only the dial should be used as an indication of the pressure in the canner. One manufacturer now makes a dual-gauge canner; read the manufacturer’s user manual for information on when and how to use either the weighted gauge or the dial.
Pressure canners come deep enough for one layer of quart or smaller size jars, or deep enough for two layers of pint or smaller size jars. The USDA recommends that a canner be large enough to hold at least 4 quart jars to be considered a pressure canner for the USDA published processes.
Serious errors in processes obtained in pressure canners can occur if any of the following conditions exist:
Follow these steps for successful pressure canning:
(Read through all the instructions before beginning.)
Make sure the pressure canner is working properly before preparing food. Clean lid gaskets and other parts according to the manufacturer’s directions; make sure all vent pipes are clear and contain no trapped material or mineral deposits. Center the canner over the burner. The burner and range must be level. Your pressure canner can be damaged if the burner puts out too much heat. In general, do not use on an outdoor LP gas burner or gas range burner over 12,000 BTU’s. Check your manufacturer’s directions for more information about appropriate burners.
Put the rack and hot water into the canner. If the amount of water is not specified with a given food, use enough water so it is 2 to 3 inches high in the canner. Longer processes required more water. Some specific products (for example, smoked fish) require that you start with even more water in the canner. Always follow the directions with USDA processes for specific foods if they require more water be added to the canner.
For hot packed foods, you can bring the water to 180 degrees F. ahead of time, but be careful not to boil the water or heat it long enough for the depth to decrease. For raw packed foods, the water should only be brought to 140 degrees F.
While the canner is cooling, it is also de-pressurizing. Do not force cool the canner. Forced cooling may result in food spoilage. Cooling the canner with cold running water or opening the vent pipe before the canner is fully depressurized are types of forced cooling. They will also cause loss of liquid from jars and seal failures. Forced cooling may also warp the canner lid.
Even after a dial gauge canner has cooled until the dial reads zero pounds pressure, be cautious in removing the weight from the vent pipe. Tilt the weight slightly to make sure no steam escapes before pulling it all the way off. Newer canners will also have a cover lock in the lid or handle that must release after cooling before the lids are twisted off. Do not force the lid open if the cover locks are not released. Manufacturers will provide more detailed instructions for particular models.
Depressurization of older canner models without dial gauges should be timed. Standard size heavy-walled canners require about 30 minutes when loaded with pints and 45 minutes when loaded with quarts. Newer thin-walled canners cool more rapidly and are equipped with vent locks that are designed to open when the pressure is gone. These canners are depressurized when the piston in the vent lock drops to a normal position. Some of these locks are hidden in handles and cannot be seen; however, the lid will not turn open until the lock is released.
Reprinted with permission from the University of Georgia.
Andress, E. (2011rev.). Preserving Food: Using Pressure Canners. Athens, GA: University of Georgia, Cooperative Extension.
The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The University of Georgia Cooperative Extension and the Colleges of Agricultural and Environmental Sciences & Family and Consumer Sciences offer educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.
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