Acid foods - Foods which contain enough acid to result in a pH of 4⅗ or lower. Includes all fruits except figs; most tomatoes; fermented and pickled vegetables; relishes; and jams, jellies, and marmalades.
Acid foods may be processed in boiling water.
Altitude - The vertical elevation of a location above sea level.
Ascorbic acid - The chemical name for vitamin C. Lemon juice contains large quantities of ascorbic acid and is commonly used to prevent browning of peeled, light-colored fruits and vegetables.
Bacteria - A large group of one-celled microorganisms widely distributed in nature. See microorganism.
Blancher - A 6 to 8 quart lidded pot designed with a fitted perforated basket to hold food in boiling water, or with a fitted rack to steam foods. Useful for loosening skins on fruits to be peeled, or for heating foods to be hot packed. Boiling-water canner - A large standard-sized lidded kettle with jar rack, designed for heat-processing 7 quarts or 8 to 9 pints in boiling water.
Botulism - An illness caused by eating toxin produced by growth of Clostridium botulinum bacteria in moist, low-acid food, containing less than 2 percent oxygen, and stored between 40 degrees and 120 degrees F. Proper heat processing destroys this bacterium in canned food. Freezer temperatures inhibit its growth in frozen food. Low moisture controls its growth in dried food. High oxygen controls its growth in fresh foods.
Canning - A method of preserving food in air-tight vacuum-sealed containers and heat processing sufficiently to enable storing the food at normal-home temperatures.
Canning salt - Also called pickling salt. It is regular table salt without the anticaking or iodine additives.
Citric acid - A form of acid that can be added to canned foods. It increases the acidity of low-acid foods and may improve the flavor and color.
Cold pack - Canning procedure in which jars are filled with raw food.
"Raw pack" is the preferred term for describing this practice. "Cold pack" is often used incorrectly to refer to foods that are open-kettle canned or jars that are heat-processed in boiling water.
Enzymes - Proteins in food which accelerate many flavor, color, texture, and nutritional changes, especially when food is cut, sliced, crushed, bruised, and exposed to air. Proper blanching or hot-packing practices destroy enzymes and improve food quality.
Exhausting - Removal of air from within and around food and from jars and canners. Blanching exhausts air from live food tissues.
Exhausting or venting of pressure canners is necessary to prevent a risk of botulism in low-acid canned foods.
Fermentation - Changes in food caused by intentional growth of bacteria, yeast, or mold. Native bacteria ferment natural sugars to lactic acid, a major flavoring and preservative in sauerkraut and in naturally fermented dills. Alcohol, vinegar, and some dairy products are also fermented foods.
Headspace - The unfilled space above food or liquid in jars. Allows for food expansion as jars are heated, and for forming vacuums as jars cool.
Heat processing - Treatment of jars with sufficient heat to enable storing food at normal home temperatures.
Hermetic seal - An absolutely airtight container seal which prevents reentry of air or microorganisms into packaged foods.
Hot pack - Heating of raw food in boiling water or steam and filling it hot into jars.
Low-acid foods - Foods which contain very little acid and have a pH above 4⅗. The acidity in these foods is insufficient to prevent the growth of the bacterium Clostridium botulinum. Vegetables, some tomatoes, figs, all meats, fish, seafoods, and some dairy foods are low acid. To control all risks of botulism, jars of these foods must be (1) heat processed in a pressure canner, or (2) acidified to a pH of 4⅗ or lower before processing in boiling water.
======================================================= === * USDA Agriculture Information Bulletin No. 539 (rev. 1994) * Meal-Master format courtesy of Karen Mintzias
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