Pressure Canning and Water Bath Canning: Explained

If you are new to canning, deciding between water bath (boiling-water) canning and pressure canning can be challenging. Water bath canning seems easier, and works for more acidic vegetables, fruits and pickles, but cannot be used for low-acid foods such as red meat, fish, seafood, and some vegetables… you will need a pressure canner. If you want to know a brief history of food canning, read Food Canning and its History.

Pressure Canner:

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Water bath Canner:

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The United States Department of Agriculture recommends the pressure canner as being the only safe method for canning low acid food — vegetables, meats, and poultry.

There are invisible microorganisms present all around us. Fruits, vegetables, and meat contain these microorganism naturally, and yet, they are not a problem unless food is left to sit for extended periods of time, causing food spoilage. This is nature’s way of telling us when food is no longer fit to eat.

There are four basic agents of food spoilage — enzymes, mold, yeast, and bacteria. Canning interrupts the natural spoilage cycle so food can be preserved safely. Molds, yeast and enzymes are destroyed at temperatures below 212*F (100*C), the temperature at which water boils (except in mountainous regions). Therefore, boiling water processing is sufficient to destroy those agents.

Bacteria, however, are not as easily destroyed. The bacteria, Clostridium botulinum produces a spore that makes a poisonous toxin which causes botulism. This spore is not destroyed at 212*F (100*C). In addition, the bacteria thrive on low acid foods in the absence of air. For a safe food product, low acid foods need to be processed at 240*F (115*C), which can be achieved only with a pressure canner.

In pressure canning, some of the water canner is converted to steam, which creates pressure within the canner. As pressure increases, temperature increases., 5 pounds pressure — 228*F (105*C) 10 pounds pressure — 240*F (115*C). This pressurized heat destroys the potentially harmful bacterial spores. As the jars cool, a vacuum is formed (a popping sound), sealing the food within and preventing any new microorganisms from entering and spoiling the food.

As a safeguard against using canned food which may be affected with spoilage that is not readily detected, boil all low acid foods and tomatoes for 10 minutes at altitudes below 1,000 feet. Extend the boiling time by 1 minute for each 1,000 foot increase in altitude.

Many times odors that cannot be detected in the cold product will become evident by this method. If, after boiling, food does not smell of look right, discard it without tasting.

CANNING JARS (MASON JARS): While there are many styles and shapes of glass jars on the market, only Mason jars are recommended for home canning. Mason jars are available in 1/2 pint, pint, and quart capacities with threads on which a cap may be screwed.

CLOSURES FOR MASON JARS: The two-piece vacuum cap consists of a flat metal lid held in place with a screw band. A rubber compound on the underside of the lid forms a seal during processing. Follow the closure manufacturer’s directions for using the two-piece cap and for testing for a proper seal. If the jar has not sealed, check the jar lip for nicks/cracks or some food particles that gets in between the metal lid. Unsealed jars can be completely reprocessed or use the food immediately.

Source: GoPresto.com (Pressure Canner and Cooker Instruction manual)

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Canning Kit:

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IMPORTANT REMINDER IN CANNING FOODS:

1.Follow the step-by-step instructions for pressure or water bath canning in your canning manual. Prepare food according to the directions in specific recipe.

2. Be sure your canner is thoroughly cleaned and working properly. Check each parts before using. Replace the ones that are worn and deformed.

3. Check mason/canning jars for nicks, cracks, and sharp edges. Check screw bands for dents or rust. Use only jars, lids, and bands in perfect condition so an airtight seal may be obtained. Wash and rinse jars, lids, and bands. Pour hot water or you may wash in the dish water [using hot water and drying] and set aside until needed.

. The best way to sterilize jars is to wash them in boiling water after soaping and rinsing if you do not have a dish washer and jars are really dirty. Follow manufacturer’s manual for specific instruction. Do not boil, jar lids as it may warp the rubber. Wash is in hot water but not boiling water. Wash rings as well but not necessarily in hot water.

4. Select fresh firm food. Sort food according to sizes. Clean food thoroughly. Prepare according to recipe. Fill hot Mason jars promptly with food and liquid to recommended level. Allow 1/2-inch headspace for fruits. ALL vegetables and meats require 1-inch headspace due to expansion during processing. Work out air bubbles with a clean nonmetallic spatula. WIPE sealing edge clean with a damp cloth.

5. Follow instructions in the canning manual which accompanied your range for recommended heat setting and processing time.

6. When the processing is done always lift the canner cover toward you to keep steam away from you when opening.

7. Using a jar lifter carefully remove jars from the canner, set jars upright on board or cloth away from draft to cool. You will hear a popping sound when the jar is cooling off as the vacuum is formed, sealing the food within. When jars are cold, test seal (the middle part of the metal lid should be sucked down, not bulged), remove bands, wipe jars, label, date, and store in a cool, dry place.

Photo attachment from Google images.

More information on:

http://nchfp.uga.edu/publications/publications_usda.html

http://www.motherearthnews.com/real-food/water-bath-pressure-canning-zecz11zsmi.aspx#ixzz3Bj5foCHV

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7 thoughts on “Pressure Canning and Water Bath Canning: Explained

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