Processing Methods

The application of the heat to food in the jar is called "processing."

Regardless of the good condition of the food or its method of preparation, foods will spoil if not processed for the required length of time and at the correct temperature.

Pressure Cooker

MEATS OF ALL KINDS and ALL VEGETABLES except tomatoes, sauerkraut and ripe pimiento peppers ARE LOW-ACID FOODS. A PRESSURE COOKER is recommended for processing these low-acid foods, as it gives a greater degree of safety.

A pressure cooker must be fitted with a rack in the bottom, steam tight cover, petcock, safety valve, and an accurate pressure gauge, or weight which measures definite pressure. The jars of food processed in a a pressure cooker reach temperatures many degrees above the boiling point of water. Read carefully the instructions for operating the type of pressure cooker being used. The general steps which apply to all types of cooker are as follows:

  1. Prepare jars and food according to steps 1, 2, 3 and 4 under Raw of Hot Pack canning on page 4.
  2. When food is ready to be packed in jars, set cooker on heat. Place rack in bottom of cooker and add boiling water to a depth of one inch for small cookers and two inches for larger cookers.
  3. As each jar is filled and cap tightened, set it on the rack in cooker to keep hot. Pack only enough jars at one time to fill cooker. Set jars apart so steam can circulate freely.
  4. Adjust the cover of cooker and fasten securely.
  5. Exhaust cooker. For cooker with gauge, leave petcock open and let steam escape freely for 7 to 10 minutes. Close petcock and when required amount of pressure is shown on gauge, start counting processing time. Adjust heat to keep pressure uniform. When cooker has a weight control, leave it off the vent pipe until steam is coming from vent in a steady stream. Then select desired pressure and place weight over vent pipe. When control jiggles, start counting processing time. Adjust heat so control jiggles only about 2 or 3 times per minute.
  6. Process for required length of time (see time tables, pages 8 and 9).
  7. As soon as processing time is up, remove cooker from heat. Make no attempt to lower pressure. Let cooker stand until hand on pressure gauge returns to zero. Then open petcock gradually and remove cover. For cooker with weight control—nudge it. If no steam escapes, pressure is down. Remove weight and cover from cooker.
  8. Food in jars may be boiling vigorously; if so, allow them to remain in cooker for a few minutes, then remove. Do not tighted screw bands on KERR Mason Caps. Set jars upright 2 or 3 inches apart on several thicknesses of cloth, to cool. Do not set hot jars in a draft or on a cold, wet surface. Do not cover them.
  9. When jars are cold test for seal (page 5) and remove screw bands. The U.S. Department of Agriculture recommends the use of a pressure cooker for canning low-acid vegetables and meats.
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Pressure Sauce Pan

If pressure sauce pans are equipped with a gauge or weight for showing and controlling pressure at 10 pounds, they appear to be satisfactory for canning. Most authorities recommend adding 20 minutes to the pressure cooker time for pint jars to make up for the quick climb in temperature at the beginning of the process and for the more rapid cooling to zero at the finish.

For operating the pressure sauce pan for canning, follow the canning instructions given by the manufacturer of the type of pan used, but after processing DO NOT lower pressure with cold water.

Boiling Water Bath

The boiling water bath is preferable for processing fruits and tomatoes. They are acid foods and can be canned safely at boiling temperature. A pressure cooker is recommended for processing vegetables, meats and low-acid foods.

A water bath canner may be purchased or can be made from a large kettle or pail that is deep enough to permit water to cover jars at least one inch over the top and a little extra space for boiling. The canner must have a rack to hold jars at least one-half inch above the bottom of canner. The rack may be made of wooden strips, wire or other perforated material but must be put together so it sill allow water to circulate. The canner should have a cover which will make it possible to keep water at a good rolling boil all during processing.

  1. Before the preparation of the food is begun, place the water bath canner on the heat with sufficient water to cover the jars at least one inch over the top. This permits water to be heating while food is being prepared. Water should be boiling when jars of food are placed into it.
  2. Prepare and pack food and tighten KERR cap according the directions for Raw or Hot Pack canning as given on page 4. Prepare only enough jars of food at one time to fill the canner. Work rapidly so as little time as possible will elapse between precooking or packing the food and getting it into the canner.
  3. Place the jars of food on the rack in the canner far enough apart to allow the free circulation of water around them. If water does not cover jars at least one inch over the top, add boiling water to this height. Start counting processing time as soon as the water in canner reaches a good rolling boil. Keep the water boiling all during the processing period. If water boils down add sufficient boiling water to keep it at the required height.
  4. Process the required length of time (see time tables, pages 8 and 9).
  5. As soon as the processing time is up, remove jars from canner. Do not tighten screw bands on KERR Mason Caps. Set jars upright 2 or 3 inches apart on several thicknesses of cloth, to cool. Do not set hot jars in a draft or on a cold, wet surface. Do not cover them.
  6. When jars are cold, test for seal (page 5) and remove screw bands.

Sterilizing and Preparing KERR Jars and Lids

To sterilize Jars for Open Kettle Canning, wash thoroughly with soap and warm water. Rinse well, place in pan having folded cloth or rack on the bottom. Cover jars with water. Boil for 15 minutes. Jars should remain in this hot water until ready for use.

To prepare jars when food is to be processed in them, follow step No. 2 on page 4.

To prepare lids for canning, follow step No. 2 on pages 4 and 5. Screw bands must be clean and in good condition but will not require scalding.

If screw bands are rusty or have top edge pried up, they should not be used. They will cause sealing failures.

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