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Preserving Nature’s Bounty. Principles of Home Canning. How Canning Preserves Foods. Control growth of undesirable microorganisms Bacteria Molds Yeasts Control activity of enzymes Control Reactions with oxygen Moisture Loss. Proper Canning Practices.
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Preserving Nature’s Bounty Principles of Home Canning
How Canning Preserves Foods • Control growth of undesirable microorganisms • Bacteria • Molds • Yeasts • Control activity of enzymes • Control • Reactions with oxygen • Moisture Loss
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
Proper Canning Practices • Using acceptable jars and self-sealing lids • Processing jars in a boiling-water or pressure canner for the correct time
Not recommended • Open-kettle canning • Microwave canning • Dishwasher canning • Oven canning Open-kettle canning
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
Temperatures • 0o F • Freezing • Temporarily stops growth of microbes, does not kill
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
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
Use Mason Jars • ½ pint • Pint • Quart • ½ gallon (for high-acid juices only)
Rings Seals (cannot be reused) Use Two-Piece Lids
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)
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
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
Filling Jars • Fill clean jars with food • Remove excess air • Wipe rims • Apply lids and rings • Tighten fingertip tight
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
For more information on preserving foods safely, contact Pat Whitaker,Extension Agent Family & Consumer Sciences Rutherford County Developed by Janie Burney, PhD, RDProfessor, Family and Consumer Sciences