Presto precise Instructions And Recipes Manual page 5

Foods naturally high in acid and acidified foods having a pH of 4.6 or less may be safely processed using the boiling water method.
Step-by-step instructions for Boiling Water Canning begin on page 17.
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, the bacteria thrive on low-acid foods in the absence of air.
According to the United States Department of Agriculture (USDA), pressure canning is the only safe method of processing low-acid
foods (vegetables, meats, poultry, fish, and seafood).
In pressure canning, some of the water in the canner is converted to steam, which creates pressure within the canner. As pressure
increases, temperature increases: 5 pounds pressure—228°F, 10 pounds pressure—240°F, 15 pounds pressure—250°F. This pressur-
ized heat destroys the potentially harmful bacterial spores. Step-by-step instructions for Pressure Canning begin on page 7.
As jars cool after processing (by either the boiling water or pressure canning method), a vacuum is formed, sealing food within and
preventing any new microorganisms from entering and spoiling the foods.
Before Beginning
Selecting a recipe
To produce home canned food that is safe for storage at room temperature, it is necessary to use a tested canning recipe. Recipes that
have been handed down through the years or those found on the web are oftentimes unreliable and usually do not include scientifically
tested processing procedures that are vital to a successful and safe canning project. Canning information published prior to 1994 may
be incorrect and could pose a serious health risk. A tested canning recipe has been evaluated to determine the accurate processing
method (boiling water canning or pressure canning) as well as the processing time.
Always choose recipes from a reliable resource, such as the National Center for Home Food Preservation (nchfp.uga.edu), your local
Cooperative Extension Service, or this instruction book.
Selecting Jars
Glass home canning 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 (half-pint, pint, and quart jars) and will withstand
the heat of a pressure canner. The diameter of Mason jars may vary from one manufacturer to another.
Before filling Mason jars, test load your canner. It may be necessary to double-deck half-pint jars to reach the maximum capacity of
your canner, as indicated in the chart on page 4. To double-deck, stagger the jars by placing one jar on top of two (Fig. I, page 4). Jars
may touch.
The canning rack which accompanied your canner must be placed on the bottom of the canner to prevent jar breakage. Although it
is not necessary to use a rack between layers of jars, if you wish to do so, a rack can be ordered from the Presto Consumer Service
Department (see page 30).
Canning Lids and Bands
The two-piece vacuum cap (lid and band) is the recommended closure for home canning. It consists of a flat metal lid with a sealing
compound on the outer edge and a separate metal screw band that secures the lid during processing. The flat lid is for one use only
while the bands can be used repeatedly if they remain in good condition. Do not use dented or rusty bands. Use only jars, lids, and
screw bands in perfect condition so an airtight seal may be obtained.
Measuring Headspace
Headspace is the air space between the top of the food or its liquid and the lid. Leaving too much headspace can result in
underprocessing because it may take too long to release the air from the jar. 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 ½-inch headspace for fruits and tomatoes and 1-inch for
vegetables, meats, poultry, and seafood. All recipes will indicate the amount of headspace necessary for the food being canned.
Removing Air Bubbles
After food has been packed in jars, any air bubbles must be removed. Trapped air bubbles may rise to the top during processing,
causing too much headspace. Work quickly to remove air bubbles that have become trapped between the pieces of food by moving a
clean, nonmetallic spatula around the jar between the food and side of the jar.
Preparing Jar Rims and Adjusting Lids
Immediately wipe jar rims with a clean, damp cloth to remove any residue. Any food particles, such as seeds, grease, or syrup, on the
rim of the jar may prevent the jar from sealing. Place flat lid on rim of jar, making sure sealing compound is touching glass. Position
a band over the lid and, using fingertips, screw onto the jar just until resistance is met. Do not overtighten as air must release from the
jars during processing and cooling.
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