We're quickly approaching the intense canning period here on the Kenai Peninsula. One of the most frequently asked questions during this time usually has to do with jars.
There is usually some confusion about when to and when not to sterilize jars in home canning food.
Jars should be cleaned before every use in hot water with detergent and rinsed well. Unrinsed detergents may cause unnatural flavors and colors. Washed by hand or dishwasher, either is acceptable.
These washing methods do not sterilize jars. (A side note: Hard water films on jars may be removed by soaking jars several hours in a solution of 1 cup vinegar per gallon of water.)
All jams, jellies and pickled products processed less than 10 minutes should be filled into sterilized empty jars.
To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner with hot, not boiling, water to one inch above the tops of the jars. Boil for 10 minutes. Remove and drain hot jars one at a time. Use immediately.
Jars to be used for vegetables, meat, fish and fruits to be processed in a pressures canner need not be sterilized.
It also is unnecessary to sterilize jars for fruits, tomatoes and pickled or fermented foods that will be processed 10 minutes or longer in a boiling-water canner.
Handle jars carefully. Use nonabrasive sponges and cleaners when cleaning jars. Use nonmetallic utensils to pack food in jars, remove air bubbles from jars prior to canning and to remove food from jars.
Repeated contact with metal spoons or knives can weaken jars. Even jewelry can scratch the glass, so remove rings and bracelets when handling jars.
I also receive many questions throughout the year regarding jar breakage during the canning process. Whenever callers phone with this problem I ask them to describe the appearance of the crack. The appearance of the crack itself will give clues as to the possible causes.
Thermal shock breakage is characterized by a crack running around the base or lower part of the jar and sometimes extending up the side. Possible causes are 1) filling cold jars with boiling liquid and food; 2) filling hot jars with cold food, water or syrup; 3) not using a rack in boiling water bath canner or pressure canner; 4) setting hot jars on a cold surfaces; 5) setting hot jars to cool in a cold draft; 6) splashing hot jars with cold water; 7) cleaning jars with soap impregnated steel wool; or 8) using metal utensils in the jars.
Impact breakage is characterized by cracks radiating from the point of contact. Some of the possible causes are 1) rough handling of jar; 2) dropping, hitting or bumping glass jars; 3) damage by cleaning with soap impregnated steel wool; 4) glass scratched by dirt or sand on food; 5) glass scratched by jewelry; or 6) using metal utensils to pack food or to remove food for serving.
Pressure breakage is characterized by the origin of the break on the side. It is a vertical crack, which divides into two forks. Possible causes are 1) using the oven to process home canned foods; 2) not enough headspace to allow food to expand during canning or freezing; 3) fluctuating heat during pressure canning; 4) moving petcock or weight before all pressure has been released; or 5) force-cooling pressure canner with cold water or air.
Kerr Glass Manufacturing produced an excellent fact sheet on jar breakage. For a free copy of this fact sheet or for more information about food preservation, contact the Cooperative Extension Service.
Linda Tannehill is an agent at the Alaska Cooperative Extension Office. She is a home economist and involved in the 4-H/Youth Develop--ment programs. The Kenai Peninsula District Extension Office is at 43961 Kalifornsky Beach Road, Suite A, Soldotna, AK. The phone number is 262-5824 or toll-free at (800) 478-5824.
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