Mother Earth Living

Home Canning 101: How to Can at Home

Enjoy fresh, local food all year long by canning your own produce at home.
By Mary Clemens Meyer and Susanna Meyer
October 2010 Web

"Saving the Seasons" offers clear instructions, step-by-step pictures, tips, charts and user-friendly recipes to help beginners and experts alike enjoy the season's bounty all year long.
Photo Courtesy Herald Press


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The following is an excerpt from Saving the Seasons: How to Can, Freeze, or Dry Almost Anything by Mary Clemens Meyer and Susanna Meyer (Herald Press, 2010). The excerpt is part of a chapter titled "Canning." 

Canning preserves food by sealing it airtight in glass jars. The heating process that causes the jar to seal kills bacteria, molds, and enzymes that spoil food; the airtight seal keeps them out.

Advantages: Canned foods do not need to be refrigerated. Store them on a shelf in a dark, cool place for a year or more—no energy use is required after the canning process. Canned foods are ready to use; there’s no need to thaw or cook. They make delicious, ready-made gifts.

Disadvantages: Foods lose some nutritional value because of the high temperatures used in canning. Some fruits and vegetables should not be canned because of significant changes in taste or texture. Canning food can be a long process, and a hot one on summer days!

Basics 

Plan to can when produce is in season. If you don’t have your own garden, check with local farmers about buying larger quantities of produce.

High-acid foods—such as fruits, pickles, and tomatoes—may be canned with the boiling bath water method. Low-acid foods—such as meats, poultry, and vegetables that are not pickled—must be processed by pressure canning.

Can fruits and vegetables when fully ripe but not overripe. Check them and discard pieces with unusual odors, oozing spots, or discoloration. (Small bruises or overripe spots may be cut out.)

Read the recipe and gather all supplies before beginning. Use jars specially made for canning; they have tempered glass to withstand high temperatures. Check the top rim of each jar for cracks and chips that would prevent a good seal.

Most canning jars come with two-piece lids. You can use the metal screw bands many times, until they become rusty, but each flat sealing lid should be used just once. You can buy extra boxes of flat lids or two-piece lids.

Wash food carefully and thoroughly clean utensils. Wash jars in hot, soapy water before using. The high temperatures during processing will sterilize them along with the food.

Canning at Higher Elevations 

At elevations from 1,001 to 3,000 feet/305 to 915 m, add 5 minutes to boiling water bath processing time; from 3,001 to 6,000 feet/906 to 1,830 m, add 10 minutes; higher than 6,000 feet/1,830 m, add 15 minutes.

For most pressure canners, increase pressure from 10 to 15 pounds/4.5 to 6.8 kg at elevations over 1,000 feet/300 m. (Check canner instructions for more details.)

BPA and Food Preservation 

Bisphenol-A, commonly abbreviated BPA, is a chemical used to make polycarbonate plastics. BPA is used to line many food containers, including metal cans. BPA easily leaches into food and liquids, and has been shown to mimic estrogen, causing reproductive and developmental problems, along with cancer, heart disease and diabetes.

One great advantage to preserving in glass is avoiding this common chemical. However, most canning jar lids are lined with plastic that includes BPA. Because BPA only becomes a problem when it comes in contact with foods or liquids, you may feel safe enough using these lids. If you are particularly concerned about limiting exposure to BPA, consider glass lids with rubber rings and metal clasps. German-made Weck canning jars, with glass lids, are available online at www.weckcanning.com.

For the same reasons, we recommend freezing in freezer-safe glass, stainless steel, or BPA-free plastics. Stainless steel ice cube trays can be found online, and are particularly handy for freezing baby food.

Where to Buy Supplies 

Look for canning supplies at hardware stores, kitchen shops, or in large grocery stores. They are usually easy to find at general stores and bulk food stores in areas where the Amish live. In urban areas, call local grocery stores to see if they carry canning supplies. Supplies are also available online fro various sellers, including Lehman’s (www.lehmans.com) in Kidron, Ohio, which loaned supplies for the photos in this book.

Terms 

Boiling Water Bath: Canning process for high-acid foods (fruits, pickles, tomatoes) in which jars of food are covered with boiling water for a period of time.

Pressure Canning: Canning process for low-acid foods (meat, poultry, most vegetables) in which jars of food are heated to high temperatures with steam pressure.

Canner: Large enamelware or stainless steel pot used for boiling water bath process. Includes a rack with handles that can sit on the rim and be lowered into boiling water.

Pressure Canner: Canner made of heavy-gauge stainless steel for processing with steam pressure. Lid is fitted with a safety valve, petcock or steam vent, and pressure gauge.

Cold Pack: To pack cold or raw food in jars for canning.

Hot Pack: To blanch (heat in water and cool quickly) or cook food and pack in hot jars for canning.

Headspace: Amount of space left at top of jar when packing food for canning. If filled too full, food could bubble out during processing and prevent a proper seal on the jar. Headspace varies from ¼ to 1 inch/6 mm to 2.5 cm.

How to Can 

General Guidelines

• Handle glass jars carefully to keep them from breaking or cracking because of a sudden temperature change. Do not pour boiling liquid into a cool jar. Warm the jar first by setting it in hot water. Do not place hot jars on a cold or wet surface, or in a draft.

• Prepare only one canner load of food at a time, so that partially processed food stands for only a short time.

• Pour boiling water over jar lids in a bowl and let them sit in hot water until ready to place on jars. This softens the rubbery seal and helps the lid fit tightly on the rim.

• After filling jars, check for air bubbles in each jar. Carefully run a narrow spatula between food and jar, if needed, to allow bubbles to escape.

• Wipe rims of jars thoroughly after filling to remove bits of food that might prevent the lid from sealing.

• Tighten metal bands firmly over lids with hands. Lids should be just “fingertip tight” to allow some air to escape during processing.

• There are two methods of canning food: the boiling water bath process and pressure canning.

Boiling Water Bath 

Fill canner half full with water and heat on stove at medium heat while filling jars. (If you have only a few jars, or are canning half-pint/250 ml jars, you can use a large cooking pot in place of a large canner. The pot must have a rack in the bottom to keep jars from touching the bottom of cooker.)

As each jar is filled, set it on elevated rack in canner. When all jars are on rack, lower it into water.

Add hot water from faucet to bring water level to 1 to 2 inches/2.5 to 5 cm above tops of jars. Place lid on canner and bring water to a boil.

Lower heat slightly but be certain that water keeps boiling gently and steadily the entire time. (Depending on the processing time, you may need to lower the heat several times to keep water from boiling too rapidly.)

Using a jar lifter, remove jars from boiling water as soon as processing time is complete.

Set jars on a dry kitchen towel, out of drafts, allowing air space around each jar. Let cool 12 to 24 hours. Do not retighten metal bands.

Pressure Canning 

Place jars on rack in pressure canner and add water to a depth of 2 to 3 inches/5 to 7.5 cm. Heat water to a simmer (180º F/82º Celsius).

Fasten canner lid in place, leaving petcock or steam vent open. Adjust heat to medium-high setting until steam flows out evenly. Allow steam to escape for 7 to 10 minutes.

Close petcock or steam vent, or place weight on vent pipe, and bring pressure to the proper amount specific in canning directions.

Begin to count processing time when gauge reaches correct amount of pressure.

Maintain a consistent pressure. (The longer food cooks, the less heat it takes to maintain pressure, so you will need to lower heat several times during processing.)

As soon as the processing time is up, remove canner from heat and let stand until canner has depressurized and returned to zero pressure. Do not try to hurry cooling process, as this may cause loss of liquid in jars.

Open petcock or steam vent, or remove gauge. If no steam escapes, remove lid. Lift edge of lid away from you first to prevent being burned by hot steam.

Set jars on a dry kitchen towel, out of drafts, allowing air space around each jar. Let cool 12 to 24 hours. Do not retighten metal bands.

After Canning 

Jars should seal as they cool. You can usually hear a snap or pinging sound as a jar seals. Lids will look slightly concave when sealed. To test for a seal, press down on the center of the lid. If it is firm and doesn’t flex, the jar has a good vacuum seal.

If a lid doesn’t seal within 24 hours, you can immediately reprocess the food. Remove the lid and reheat the food according to the recipe. Pack into a clean, hot jar. Add a new, heated lid and reprocess using the canning method and processing time indicated in the recipe.

After 12 to 24 hours, you may remove the metal bands for reuse. Wipe jars clean before storing in a cool, dark place.

Label jars before storing, so you can use the oldest food first. Canned food should keep its excellent quality for at least a year but gradually deteriorates in flavor and appearance.

Check jars of food regularly before using. Any jars not properly sealed or spoiled should be discarded immediately.

Canning Safety 

A few simple precautions will ensure that your home-canned foods are safe.

1. Follow recipes and instructions.

• Canning is not the time to experiment in the kitchen. Use the exact amounts of ingredients listed in recipes.

• Can foods for the full amount of time and by the recommended method.

• If canning at high altitude, adjust times accordingly.

2. Check the seal.

• After jars have cooled, press on the center of the lid with your finger. If the lid is not completely sealed, refrigerate and use the food soon. Or, reprocess using a new jar and lid.

3. Dispose of questionable food.

• If the lid bulges or pops up, or is not tightly sealed, discard the food.

• If mold appears to be growing on the food, or it appears or smells “off,” discard the food.

Botulism and Other Safety Concerns 

Bacteria, molds, and viruses can all compromise the safety of preserved food. The clostridium botulinum spores that cause botulism thrive all around us, causing no harm. They only become a problem when they multiply exponentially and then die in an enclosed environment (like an improperly sealed canning jar). The dead bacteria produce a neurotoxin that is toxic to humans.

Following the steps listed above will eliminate virtually all bacteria, molds, and viruses from home-canned food. Spoilage is rare. If, however, you suspect that a food has spoiled, carefully wrap the entire jar in a heavy garbage bag and dispose of it.

Canning Recipes

Apple Pie Filling

Make your own canned apple pie filling at home, and you can enjoy warm apple pies all winter long!


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