Many myths exist about safe ways to can foods. The reality is that food must be processed using the right equipment and the right recipes to ensure safety. The type of canner you need depends on the food you want to preserve. A water bath canner is used to preserve acid foods like fruits and pickled foods. Low-acid foods, like vegetables and meats, must be canned in a pressure canner. Tomatoes can be processed in either type of canner, but always add lemon juice to be sure they are acid enough.
Boiling Water Bath Canner
A boiling water bath canner is simply a big pot with a removable rack to hold the jars and a fitted lid. It must be big enough to cover the jars with 1 to 2 inches of boiling water.
If you have an electric stove, be sure that the canner has a flat bottom, and that the canner is no more than 4 inches wider in diameter than the heating element or burner that you will be using. When the canner is centered on the burner, the canner should not extend more than 2 inches on any side. This is important so that all the jars will be processed uniformly.
Pressure Canner—Not Pressure Cooker
Use a pressure canner, not a pressure cooker. A pressure canner must be able to hold at least 4 quart-size jars. Most 16-quart or larger canners are big enough. All pressure canners have a removable rack, an automatic vent/cover lock, a vent port (steam vent), and a safety fuse. Only use canners that show the Underwriters Laboratories approval of safety symbol (UL).
A pressure cooker or pressure saucepan is smaller and is not intended for processing foods in jars. A pressure cooker will heat up and cool down faster than a pressure canner, and the canned foods may not be processed long enough to destroy the microorganisms. Differences in the sizes of the pressure cookers and in the thickness of the food being processed make it impossible to adjust the times safely.
Dial-gauge or Weighted-gauge Canners
Dial-gauge canners have a dial that shows the pressure. These canners must be watched during processing to be sure the pressure does not fall below the required level, and they must be tested every year to make sure the dial is registering correctly. A dial-gauge canner is a good choice for those that live at higher altitudes because precise pressure adjustments are easy to make.
Weighted-gauge canners have weights for 5, 10 or 15 pounds pressure that is placed over the vent and rock or jiggle when the correct pressure is reached. Follow the manufacturer’s instructions on how often the gauge should rock or jiggle. The sound of the weight rocking or jiggling indicates that the correct pressure is being maintained, so these canners do not need to be watched during processing. Weighted gauges do not have to be checked each year. A disadvantage for those living at higher altitudes is that precise pressure adjustments cannot be made since the canner is limited to 5, 10, or 15-pound weights with the use of a weighted gauge canner.
Check Your Pressure Canner for Safety
Whether your pressure canner is brand new, a family heirloom, or a yard sale find, be sure all parts are in good condition.
- Rubber gaskets must be flexible and soft, not brittle, sticky, or cracked. Check manufacturer’s instructions for proper care of your gasket. (Note: Not all pressure canners have gaskets.)
- Vent ports and openings must be clean and not clogged.
- The lid must not be warped and must fit properly and lock into place.
- The dial on a dial-gauge canner should be tested each year for accuracy.
- Do a test run on your canner if it is new, or at the beginning of the season.
- Put several inches of water in your canner.
- Secure the lid and seal the vent.
- Turn on the heat and make sure the canner will get to the needed pressure and maintain it without leaking.
- Practice the correct way to depressurize the canner and remove the lid.
Contact your local Extension office or the Home & Garden Information Center (1-888-656-9988) for information on how to have your dial-gauge canner tested.
- National Center for Home Food Preservation. June 2010. Can Your Vegetables Safely. http://www.uga.edu/nchfp/tips/summer/can_vegetables_safely.html
- National Center for Home Food Preservation. November 2006. Burning Issue: Canning in Pressure Cookers. http://www.uga.edu/nchfp/publications/nchfp/factsheets/pressurecookers.html
- National Center for Home Food Preservation. 2005. Using Boiling Water Canners. http://www.uga.edu/nchfp/publications/uga/using_bw_canners.html