Canning Food

Canning is an important, safe method for preserving food if practiced properly. The canning process involves placing foods in jars or similar containers and heating them to a temperature that destroys micro-organisms that cause food to spoil. During this heating process air is driven out of the jar and as it cools a vacuum seal is formed. This vacuum seal prevents air from getting back into the product bringing with it contaminating micro-organisms.

Safe Canning Methods

There are two safe ways of processing food, the boiling water bath method and the pressure canner method:

• The boiling water bath method is safe for tomatoes, fruits, jams, jellies, pickles and other preserves. In this method, jars of food are heated completely covered with boiling water (212F at sea level) and cooked for a specified amount of time
• Pressure canning is the only safe method of preserving vegetables, meats, poultry and seafood. Jars of food are placed in 2 to 3 inches of water in a special pressure cooker which is heated to a temperature of at least 240 F. This temperature can only be reached using the pressure method. A microorganism called Clostridium botulinum is the main reason why pressure processing is necessary. Though the bacterial cells are killed at boiling temperatures, they can form spores that can withstand these temperatures. The spores grow well in low acid foods, in the absence of air, such as in canned low acidic foods like meats and vegetables. When the spores begin to grow, they produce the deadly botulinum toxins(poisons).

The only way to destroy these spores is by pressure cooking the food at a temperature of 240F, or above, for a specified amount of time depending on the type of food and altitude.

Foods that are low acid have a pH of more than 4.6 and because of the danger of botulism, they must be prepared in a pressure canner.

The low acidic foods include:
• Meats
• Seafood
• Poultry
• Dairy products
• Fresh Picked Vegetables

High acid foods have a pH of 4.6 or less and contain enough acid so that the Clostridium botulinum spores can not grow and produce their deadly toxin. High acidic foods can be safely canned using the boiling water bath method.

The high acidic foods include:
• Fruits
• Pickled vegetables
• Tomatoes

Other foods that may be canned are:

• Nuts
• Salsa

Certain foods like, tomatoes and figs, that have a pH value close to 4.6 need to have acid added to them in order to use the water bath method. This is accomplished by adding lemon juice of citric acid. Water Bath Canners

A water bath canner is a large cooking pot, with a tight fitting lid and a wire or wooden rack that keeps jars from touching each other. The rack allows the boiling water to flow around and underneath jars for a more even processing of the contents. The rack also keeps jars from bumping each other and cracking or breaking. If a rack is not available, clean cotton dish towels or similar can be used to pack around jars. If a standard canner is not available any large metal container may be used as long as it is deep enough for l to 2 inches of briskly boiling water to cover the jars. The diameter of the canner should be no more than 4 inches wider than the diameter of your stove's burner to ensure proper heating of all jars. Using a wash kettle that fits over two burners is not recommended because the middle jars do not get enough heat. For an electric range, the canner must have a flat bottom. Outdoor fire pits with a solid grate will also work however close attention is required to insure proper boiling temperature.

Pressure Canners

A pressure canner is a specially-made heavy pot with a lid that can be closed steam-tight. The lid is fitted with a vent (or pet-cock), a dial or weighted pressure gauge and a safety fuse. Newer models have an extra cover-lock as an added precaution. It may or may not have a gasket. The pressure pot also has a rack. Because each type is different, be sure to read the directions for operating.
Jars

Mason jars and Ball jars specifically designed for home canning are best. Commercial mayonnaise jars, baby food and pickle jars should not be used. The mouths of the jars may not be appropriate for the sealing lids and the jars are not made with heavy glass and they are not heat treated.

Jars come in a variety of sizes from half-pint jars to half-gallon jars. Pint and quart Ball jars are the most commonly used sizes and are available in regular and wide-mouth tops. If properly used, jars may be reused indefinitely as long as they are kept in good condition.

Atlas jars should not be used for home preserving and canning.

Jar Lids

Most canning jars sold today use a two piece self-sealing lid which consists of a flat metal disc with a rubber-type sealing compound around one side near the outer edge, and a separate screw-type metal band. The flat lid may only be used once but the screw band can be used over as long as it is cleaned well and does not begin to rust.

Canning Utensils

Helpful items for home canning and preserving:

• Jar lifter: essential for easy removal of hot jars.
• Jar funnel: helps in pouring and packing of liquid and small food items into canning jars.
• Lid wand: magnetized wand for removing treated jar lids from hot water.
• Clean cloths: handy to have for wiping jar rims, spills and general cleanup.
• Knives: for preparing food.
• Narrow, flat rubber spatula: for removing trapped air bubbles before sealing jars.
• Timer or clock: for accurate food processing time.
• Hot pads
• Cutting board

When looking for advice and information on preserving food, try to avoid old pamphlets, outdated cookbooks, untrained celebrities and undocumented food shows on TV. Your best source for current information on research and processing instructions are publications made by the U.S. Food and Agriculture Department, College Cooperative Extension Services and major food processing equipment manufactures.