Download - Department of Family and Consumer Sciences 1 Preserving Natures Bounty Principles of Home Canning
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Preserving Nature’s BountyPrinciples of Home Canning
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How Canning Preserves Foods
• Control growth of undesirable microorganisms– Bacteria– Molds– Yeasts
• Control activity of enzymes• Control
– Reactions with oxygen– Moisture Loss
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Proper Canning Practices
• Carefully selecting and washing fresh food
• Peeling some fresh foods• Hot packing many foods• Adding acids (lemon juice or
vinegar) to some foods
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Proper Canning Practices
• Using acceptable jars and self-sealing lids
• Processing jars in a boiling-water or pressure canner for the correct time
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Not recommended• Open-kettle
canning• Microwave
canning• Dishwasher
canning• Oven canning
Open-kettle canning
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Temperatures• 2400 F – low acid foods
– Pressure canning– Kills bacterial spores
• 2120 F – high acid foods– Water-bath canning– Kills molds, yeasts and some
bacteria
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Temperatures• 0o F
– Freezing– Temporarily stops growth of
microbes, does not kill
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How Canning Works• Air is driven from the jar or
can• A vacuum seal is formed• Prevents air (with
microorganisms) from getting back into food
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The Effect of Altitude• Affects how long food is processed; water boils at lower
temperatures as altitude increases• For water-bath canning: Add time for higher altitudes• For pressure-canning: Add pressure for higher altitudes• Tennessee Valley varies from 2000-2500 feet
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Use Mason Jars
• ½ pint• Pint• Quart• ½ gallon
(for high-acid juices only)
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Use Two-Piece Lids
•Rings•Seals (cannot be reused)
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Jars to Avoid• Old-style jars
– Wire bails and zinc lids– Cannot be fitted and sealed
• Commercial jars– Mayonnaise, peanut butter,
etc.– Narrower sealing surface– Less tempered (will
break in pressure canners)
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Raw or Hot Pack• Raw-Pack
– Pack jars with uncooked product
• Hot-Pack – Pack jars with cooked product– Maintains better color over time– Removes more air
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Control Headspace• Space between product
and lid– ¼ inch for jams and jellies– ½ inch for fruits and tomatoes– 1 to 1 ¼ inch for foods processed in
pressure canners
• Too much space, takes too long to drive out air
• Too little space, may not seal
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Filling Jars• Fill clean jars with
food• Remove excess air• Wipe rims• Apply lids and
rings• Tighten fingertip
tight
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General Principles• Follow tested recipes• Do not alter ingredients• Use water-bath canner for high
acid foods, pickles, jellies• Use pressure canner for low
acid foods
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For more information on preserving foods safely, contact Pat Whitaker,Extension Agent Family & Consumer Sciences Rutherford CountyDeveloped by Janie Burney, PhD, RDProfessor, Family and Consumer Sciences