Fact Sheets And Publications
In the interest of food safety, vegetables must be processed in a pressure canner. Pressure for processing ranges between 5 pounds pressure to 15 pounds pressure, depending on the type of canner and food being processed. Processing time varies according to specific vegetable and size container.
Before Canning Season Starts –
- For dial-gauge canners, check pressure gauge for accuracy. Consult manufacturer's instruction booklet or contact your county Extension Family and Consumer Science Educator. Weighted-gauges do not require checking.
- Replace gasket (provided canner is equipped with one) if it is hard or cracked. Clean petcock and safety valve. Repeat cleaning procedure as needed during canning season. Wipe cover with sudsy cloth, then with clean cloth wrung in clear water. Do not put cover into water.
- Wash canner kettle in hot, sudsy water, then rinse and dry thoroughly.
Canning jars and lids
- Check for cracks or chips. Use only regular and wide-mouth Mason-type, threaded jars. Do not use mayonnaise, peanut butter, or other jars used for commercially canned foods to can foods in pressure canner. These jars are not made from as heavy a glass and have not undergone as high a heat-tempering process as canning jars.
- Secure a fresh supply of lids at the start of each season. Screw bands may be reused as long as they are in good condition.
General Recommendations for Packing Glass Jars
Follow a tested recipe when canning vegetables. Recommendations have changed for some foods and older recipes are not recommended. Follow directions and recipes exactly.
Raw pack - Pack tightly without crushing. Add 1/2 teaspoon salt to pints, 1 teaspoon to quarts. (Salt is for seasoning only and not necessary for preservation. Salt may be omitted if desired.) Cover with boiling water, leaving a 1-inch space at the top of jar. It is necessary to leave headspace between the lid and the top of the food or liquid because the bubbling of liquids and expansion of solids during processing. If too much product or liquid is added, contents may overflow during processing. Adjust lids and process according to the time and pressure specified in directions for each vegetable.
Hot pack - Heat vegetables as directed. Pack hot vegetables loosely to 1 inch of top. Add salt (see raw pack). Cover with boiling hot cooking liquid, or if liquid contains grit, use fresh boiling water. Leave a 1-inch space at top of the jar. Adjust lids. Process according to the time and pressure specified in directions for each vegetable.
Use of Pressure Canner
Follow directions in manufacturer's manual. If original manual has been misplaced or lost, write to manufacturer, giving model number of canner.
General rules for use.
- Put 2 to 3 inches boiling water in canner.
- Set filled jars on rack in bottom of canner. Allow space between jars so steam circulates around jars.
- Fasten canner cover securely.
- Make sure vent (petcock or weighted-gauge opening) is clear. Heat canner on high until steam escapes from vent. Allow a steady stream of steam to escape through vent for 10 minutes. This venting is necessary to replace air in the canner with steam. If this step is eliminated, the temperature in the canner will not reach the appropriate temperature and the food will not be heated adequately. Close petcock or put on weighted gauge.
- Let pressure rise to specified pounds. Start counting processing time at once. Regulate heat under canner to keep pressure steady. Fluctuations in pressure may cause liquid in jars to overflow, or food may not be processed sufficiently.
- When processing time is up, remove canner from heat at once. Let canner stand until pressure is zero. If pressure returns to zero too rapidly, liquid may be lost from jars. After pressure registers zero, slowly open petcock or remove weighted gauge. Wait 2 minutes, then unfasten lid and tilt away from you. Immediately remove jars from canner, and place them on towels or rack away from draft.
Test for Seal
Twelve to twenty-four hours after canning, check seal. Press flat metal lids at center. Lid should be slightly concave and not move when pressed in the center of the lid. Another way to test the jar seal is to tap the lid with the bottom of a teaspoon. If the jar is sealed correctly, it will make a ringing, high-pitched sound. If it makes a dull sound, the lid is not sealed or food is in contact with the underside of the lid. Do not be alarmed at popping sounds as jars cool and lids snap down.
Storage of Canned Vegetables
Remove screw bands from thoroughly cooled jars. Wash, dry, and label jars with contents and date. Store jars in cool, dry, dark place.
Is It Spoiled?
Before opening, check jars for leaks or bulging lids. When jar is opened, there may be spurting liquid, an off-odor, or mold. NEVER taste food as a check for spoilage. Home-canned vegetables may contain botulism-causing toxins if foods are not canned properly.
Before tasting or serving, boil home-canned vegetables by bringing to a full rolling boil, covering, and boiling at least 10 minutes. Boil corn and spinach 20 minutes. If any food looks spoiled, foams, or has an off-odor when heated, throw it out.
Check with your county Extension Family Consumer Science Educator for more information on food preservation.
For canning of specific vegetables, please see http://www.uga.edu/nchfp/.
Prepared by: Sue Snider, Ph.D.
Professor/Food Safety and Nutrition Specialist
Revision Date: 10/2011
UD Cooperative Extension
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