Jams, fruits and acid-rich foods such as tomatoes, pickles, pickled foods, and relishes do not need to be canned in a pressure canner. A water bath will do the job. Water bathing raises the temperature up to 212 degrees. The timing required depends on 1) how well the contents conduct heat and 2) the size jar being used, which is why quarts process longer than pints.
Low acid vegetables and meats require higher temperatures (240 degrees) in order to kill botulism caused toxins. You can only get them to 240 degrees by the use of pressure canner. The timing and pounds of pressure required depend on 1) how well the contents conduct heat and 2) the size jar being used, which is why quarts process longer than pints. The most common pressure canner, and the one I use at home, is a dial-gauge pressure canner which has a visual gauge to indicate the pressure level.
1. Raise the temperature in the contents high enough to kill bacteria, molds and yeasts.
2. Forces out the air to create a vacuum to make the jar seal.
Each canning recipe should depict which method of canning to use. Be sure to follow the directions exactly. If your recipe does not give details on which canner to use, please do not guess, consult a knowledgeable canner or purchase a canning guide. Lastly, when canning low-acid foods, please consult an Altitude Adjustment Chart as higher altitudes require more pressure and longer processing times.
Hope that helps! Can safe and enjoy~
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