Go to: Pressure Canning Index

Introduction
Canning food has been a labor of love for generations of families! What was once done out of necessity, today has become an opportunity to take control of the food you and your family consume. Abundant fresh fruits, vegetables, meats, poultry, and seafood can be savored all year. Best of all, you'll always be certain of the quality and freshness of the food in your pantry. Canning is still a labor of love, but well worth it when you take that first delightful bite of fresh flavored food you canned in your own kitchen!

Canning Basics
If you're a novice to pressure canning, this outline will give you a basic knowledge of the terminology and instruction of canning. The key to successful canning is understanding the acidity and spoilage factor of the food you wish to can, as well as the acceptable canning methods to process those foods. There are two types of food, categorized as low-acid (vegetables, meat, poultry, and seafood) and high-acid (fruits and tomatoes). Both can be successfully canned by pressure canning. However, pressure canning is the only method recommended safe for canning low-acid foods according to the United States Department of Agriculture. Boiling water method is another recommended method of processing, however this method is only acceptable for some foods. Always follow the processing method stated in the recipe.

Invisible microorganisms are present all around us. Fruits, vegetables, meat, poultry and seafood contain these microorganisms naturally. 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 will interrupt the natural spoilage cycle, so food can be preserved safely. Molds, yeast, and enzymes are destroyed at temperatures below 212° F, 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. In addition, bacteria thrive on low acids in the absence of air. Therefore, for a safe food product, low-acid foods need to be processed at 240° F. This temperature can only be achieved with a pressure canner.

Before you begin...
Prior to the canning season, pressure canners should be thoroughly examined and tested at the county extension office or with the manufacturer to ensure their proper operation. Finding a problem when there is a load of vegetables in the canner can be quite disheartening and wasteful. If this is your first canning project, do a test run with water to determine how the canner should function.

Always use current published instruction and recipe manuals. Though recipes that have been handed down through the years may hold sentimental value, they are oftentimes unreliable and usually do not include scientifically tested processing pressures and times that are vital to a successful and safe canning project. Extensive research has been conducted on canning in recent years. Canning information published prior to 1988 may be incorrect and could pose a serious health risk.

Before you begin, assemble all ingredients and supplies needed for your canning project. Carefully read, understand, and follow the recipe and canning instructions as directed. Do not substitute or omit ingredients. Always follow specific manufacturer's instructions.

Selecting Jars
Glass home cannng jars, sometimes referred to as Mason jars, are made of heat-tempered glass for durability and reuse. These are the only jars recommended for safe home canning. They are available in standard sizes and will withstand the heat of a pressure canner, time after time.

Do not use jars from commercially prepared foods such as mayonnaise and peanut butter because they were made for single-use only. Glass home canning jars offer a deep neck and wide sealing surface to assure a tight seal. Always visually examine canning jars for nicks or cracks. Recycle or discard any damaged jars.

Always use the jar size and exact processing time and pressure indicated in the recipe. Research has been conducted using half-pint, pint, and quart jars. Half-gallon jars are not recommended for pressure canning. Glass home canning jars should be thoroughly washed in hot, sudsy water. Do not use wire brushes or abrasive materials because they may damage the glass. Rinse jars completely with hot water. To help prevent jar breakage, allow jars to stand in very hot water prior to canning. A dishwasher may also be used. Wash and dry jars using a regular cycle. When cycle is complete, remove one jar at a time, keeping the rest of the jars heated until needed.

Using bands and lids
The two-piece home canning vacuum cap (lid and band) is the recommended closure for home canning. It consists of a flat metal lid with a rubber-like seal on the underside and a threaded metal screw band that secures the lid during processing. The bands can be used repeatedly if they remain in good condition, however, new lids must be used each time. Always prepare lids and bands according to manufacturer's instructions.

Avoid closures such as zinc caps and glass lids that require a jar rubber. These closures do not provide a proper method to determine if the seal is safe. Also, avoid commercial one-piece caps even if they have a rubber-like gasket because they are intended for one-time use only.

Measuring Headspace
All recipes will indicate the amount of headspace necessary for the food being canned. Headspace is the air space between the top of the food or its liquid and the lid. Leaving too much headspace can result in under processing because it may take too long to release the air from the jar. Darkening of the food at the top of the jar is also likely, however, this is not a sign of spoilage. Leaving too little headspace will trap food between the jar and the lid and may result in an inadequate seal. As a general rule, allow 1/2-inch headspace for fruits and tomatoes and 1-inch for all vegetables, meats, poultry, and seafood.

Removing Air Bubbles
After food has been packed in jars, remove air bubbles that are trapped between pieces of food with a clean, nonmetallic spatula. Wipe sealing surface wth a clean, damp cloth to remove any residue. Apply lid. Place a band over the lid and screw onto the jar just until resistance is met.

Storing Canned Food
Once jars of food have been canned and thoroughly cooled, it is important to test the seals before storing. Press down on the center of the lid. If it is concave, or stays down when pressed, the jar is properly vacuum sealed. After 12 to 24 hours, remove bands and wipe off any food residue from bands and jars. If bands are left on, they may rust and become difficult to remove. Store canned food in a cool, dark, and dry place. Home canned food can be kept for many years. However, after one year the quality will begin to deteriorate. For this reason, always date and label jars before storing. Though your memory may serve you well, squash and pumpkin will look remarkably similar when making Thanksgiving pie.

Detecting Spoilage
If up-to-date instructions are followed carefully, spoilage is uncommon. However, it is still recommended to check for signs of spoilage before tasting any canned food. Check for a broken seal, gassiness when opening, mold, sliminess, cloudiness, or unpleasant odors. If any of these signs are present, discard the food.

As a safeguard against using canned low-acid and tomato products which may be affected with spoilage that is not readily detected, boil food 10 minutes for altitudes up to 1,000 feet above sea level. 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 or look right, discard it without tasting.

Go to: Pressure Canning Index