Processing in a Pressure Canner
If you live at an altitude of 0-1000 feet, you can process foods in a weighted gauge pressure canner at 10 pounds pressure. If you are using a dial gauge pressure canner, use 11 pounds pressure. If you live at an altitude more than 2,000 feet you need to increase the pounds pressure at which you process foods. These increases are not given in this bulletin. Contact your county extension center to get this information. If tomato products are acidified, they can be safely processed in a water bath canner. If not, they must be processed in a pressure canner.
Here are some pointers for using a pressure canner:
1. Pour 2 or 3 inches of water in the bottom of the canner and heat to boiling.
2. Set jars on the rack in the canner. If you have two layers of jars in the canner, use a rack between them and stagger the second layer.
3. Fasten the canner cover securely so steam cannot escape except through the vent.
4. Once steam pours steadily from vent, let it escape for 10 minutes to drive all air from the canner. During processing, the canner must be filled with steam, not air, since it is steam that reaches the desired temperature of 240 F.
5. a. If the canner has a weighted gauge, start counting the processing time when it jiggles or rocks. The target pressure for this type of canner is 10 pounds pressure. Adjust heat so that gauge jiggles 2 or 3 times a minute or maintains a slow, steady, rocking motion.
6. b. If the canner has a dial gauge, bring pressure up quickly to 8 pounds, then adjust the heat to maintain 11 pounds pressure. Start counting the processing time when the gauge registers 11 pounds pressure. When the processing time is up, turn off the burner. (If you are using a coal or wood stove, remove canner from heat.) Let the pressure in the canner drop to zero by itself. This may take 45 minutes in a 16-quart canner filled with jars and almost an hour in a 22-quart canner. If the vent is opened before the pressure drops to zero or if the cooling is rushed by running cold water over the canner, liquid will be lost from the jars.
7. When the pressure has dropped to zero, open the vent or remove the weighted gauge. (With a weighted gauge canner, pressure is completely reduced if no steam escapes when the gauge is nudged or tilted. If steam spurts out, pressure is not yet down.)
8. Remove canner cover carefully, tilting it away from your face so that the rising steam cannot burn your face or hands.
9. Remove jars from canner. If liquid boiled out of jars during processing, do not open jars to add more liquid. Do not retighten screw bands, even if they are noticeably loose.
10. Place hot jars upright to cool on a towel or rack. Leave space between them so air can circulate. Keep jars out of drafts.
Vacuum seals form as the jars cool. When jars are cool (12 to 24 hours after processing), check the seals. If the lid is depressed or concave and will not move when pressed, it is sealed. If sealed, carefully remove screw bands. If a band sticks, loosen it by covering it for a moment with a hot, damp cloth. Bands left on jars during storage may rust, making later removal difficult.
If you find an unsealed jar, do one of the following:
* Refrigerate the food and use it within 2 to 3 days.
* Freeze the food. (Drain vegetables before freezing.)
* Reprocess the food. Remove lids, empty the contents into a pan, heat to boiling, pack into clean, hot jars, and put on new lids. Process again for the full time.
The eating quality of twice-processed food may be poor. If more than 24 hours have gone by since processing, throw out the food. It might be unsafe to eat.
Label and Store Sealed Jars
Label sealed jars with the processing date. Store them in a cool, dry, dark place. Properly stored canned foods will retain their quality for at least a year. Never store canned foods near hot pipes, a range, a furnace, or in direct sunlight because they lose quality.
If stored in a cold place, protect from freezing by wrapping the jars in newspaper or covering them with a blanket. Canned foods that do freeze may be used as long as freezing does not break the seal. However, they may not be as tasty as properly stored canned foods.
If canned foods are kept in a damp place, lids may rust.
Signs of Spoilage
Before using always check canned foods for signs of spoilage -- leakage, bulging lids, or loss of seal. Bulging or loss of seal indicates gas formation inside the jar. Upon opening the jar, look for spurting liquid. After opening, check for gassiness, cloudy liquid, disagreeable odor, or mold. Never taste food that shows any sign of spoilage. Throw it out; it might be unsafe to eat. Furthermore, never feed this food to animals; it could make them sick.
Cloudy liquid may be a sign of spoilage or be due to minerals in hard water or starch from overripe vegetables. If liquid is cloudy, check for other signs of spoilage. If there are not other signs of spoilage, boil the food. Do not eat any food that foams or has a disagreeable odor during heating.
Always boil home-canned, low-acid foods for 10 minutes before tasting. Do not use this method to make improperly processed food "safe." If enough bacteria is present (due to improper processing), boiling for ten minutes might not destroy the toxin.
Black deposits on the underside of a lid are not a sign of spoilage. The under side of canning lids is coated with enamel. If there are imperfections, such as tiny scratches or pinholes in the enamel, natural compounds in food can react with the metal in the lid to form harmless brown or black deposits.
For more information call the Extension Agent, Family and Consumer Sciences, in your county. The Cooperative Extension Service is usually listed in the telephone directory under county offices.
Processing Directions for Canning Acidified Tomatoes, Acidified Figs and Other Fruits
All processing times are given for processing in a water bath caner. Pack foods listed below to within ½ inch of the top of the jar. Source of instructions is the USDA Complete Guide to Home Canning, 1995.
Water Bath Process Water Bath Process
PACK STYLE Pints (minutes) Quarts (minutes)
Apples Wash, peel, core, and slice apples. Drain and rinse. Cook and pack. Cover with hot liquid or hot syrup. Hot only 20 20
Applesauce Prepare sauce and make sweetened or unsweetened. Hot only 15 20
Figs* Wash and drain. Do not peel or remove stems. Cover with water and boil for 2 minutes then drain. Gently boil figs in light syrup for 5 minutes. Hot only 45 50
Peaches Wash, peel and pit. Slice if desired. Drain and rinse. Pack cooked or raw. Cover with hot liquid or boiling-hot syrup. Hot or Raw 20 - Hot
25 - Raw 25 - Hot
30 - Raw
Pears Tree-ripened pears may have a coarse, gritty texture when canned. So, pickpears when they are full size but still firm and green. Hold for 2 weeks in the refrigerator then ripen them at room temperature before canning. Wash, peel, halve, and core pears. Cut into quarters if desired. Drain and rinse. Cook and pack. Cover with hot liquid or boiling-hot syrup. Hot only 20 25
Plums To can whole, prick skins in several places with table fork to prevent splitting. Freestone varieties may be halved and pitted. Pack cooked or raw. Cover with hot liquid or hot syrup. Hot or Raw 20 25
Tomatoes, acidified and packed in water To loosen skins, dip into boiling water for about 1/2 minute, then dip quickly into cold water. Peel and core. Leave small tomatoes whole. Halve or quarter larger tomatoes. Pack cooked or raw. Hot or Raw 40 45
Tomatoes, acidified* and packed in tomato juice Follow directions above except cover with hot tomato juice. Hot or Raw 85 85
Tomatoes, acidified* and packed raw without added liquid Follow directions above except when packing press tomatoes in the jars until spaces between them fill with juice. Raw only 85 85
Tomato juice, acidified* Quickly cut 1 pound of fruit into quarters -- to prevent juice from separating. Heat immediately to boiling while crushing. Continue to slowly add and crush freshly cut tomato quarters to the boiling mixture. Simmer 5 minutes after you add all pieces. Hot only 35 40
Tomato sauce, acidified* Prepare and press as for making tomato juice. Simmer until sauce reaches desired consistency. Boil until volume reduced by one-third for thin sauce; one-fourth for thick sauce. Hot only 35 40
* Add 2 tablespoons bottle lemon juice per quart or 1 tablespoon per pint; or add ½ teaspoon citric acid per quart or ¼ teaspoon per pint to the jars.
DIRECTIONS FOR CANNING VEGETABLES
Vegetables and tomatoes and figs that are not acidified are low-acid foods. All processing times are given for processing in a weighted-gauge pressure caner at 10 pounds pressure at an altitude of 0-1000 feet and in a dial-gauge pressure caner at 11 pounds pressure (at an altitude of 0-2000 feet). Source of instructions is the USDA Complete Guide to Home Canning, 1995.
Pressure Process Pressure Process
PACK STYLE Pints (minutes) Quarts (minutes)
Beans, lima Shell and wash. For both raw and hot pack, pack beans loosely into clean, hot jars. Cover with boiling hot water. Hot or Raw 40 50
Beets Sort beets for size. Cut off beet tops, leaving an inch of stem. Leave only 1 inch of root attached. Scrub beets well. Cover with boiling water until skins slip off easily, 15 to 25 minutes depending on size. Peel and trim off top and root. Leave baby beets whole. Cut medium or large beets into 1/2-inch cubes or slices. Cook and pack immediately. Cover with fresh hot water. Hot 30 35
Corn, whole kernel Husk corn and remove silk. Wash. Cut corn from cob at about 3/4 of the depth of the kernel. CAUTION: Do not scrape cobs. Pack cooked or raw. Cover with cooking liquid or fresh boiling water. Sweet corn sometimes darkens during processing due to caramelization of sugar. The sweeter the corn, the more likely it is to darken. Although the dark color is unattractive, the corn is safe to eat. Hot or Raw 55 85
Corn, cream style Follow instructions above except for cream style corn, scrape remaining corn from cobs and add to jar. To each quart of corn and scrapings, add two cups of boiling water. Heat to boiling. Add ½ teaspoon salt to each jar, if desired. Hot only 85 ---
Greens Remove tough stems and midribs. Place about 2-½ pounds greens in a cheese cloth bag and steam about 3 to 5 minutes or until well wilted. Pack loosely and cover with boiling water. Hot only 70 90
Green beans Wash and trim ends. Leave whole or cut or snap into 1-inch pieces. Hot or Raw 20 25
Mixed Vegetables 6 cups sliced carrots
6 cups cut, whole kernel sweet corn
6 cups cut green beans
6 cups shelled lima beans
4 cups whole or crushed tomatoes
4 cups diced zucchini
Wash and drain all vegetables except zucchini. Wash, trim and slice or cube zucchini. Boil for 5 minutes and pack. Cover with cooking liquid. Hot only 75 90
Peas, green Shell and wash. Cook and pack. Cover with cooking liquid or fresh boiling water. Hot or Raw 40 40
Potatoes, sweet Use small to medium potatoes. Can pieces or whole within 1 to 2 months after harvest. Wash and boil or steam (15 to 20 min). Remove skins. Cut into uniform pieces. CAUTION: Do not mash or puree pieces. Pack and cover with fresh boiling water or syrup. Hot only 65 90
Pumpkin, cubed Wash pumpkin, remove seeds, and peel. Cut into 1-inch cubes. Cook and pack. Cover with cooking liquid.
CAUTION: Only cubed pumpkin or winter squash is recommended for home canning. If desired, mash just before serving or using in recipes. Do not can mashed pumpkin or winter squash, as the product may be too thick to ensure adequate heat penetration during processing. Hot only 55 90
Squash, winter cubed Follow method for pumpkin, cubed. Hot only 55 90
Tomatoes, whole or halved packed in water Wash tomatoes. Dip in boiling water for 30 to 60 seconds until skins split; then dip in cold water. For raw pack cover with water and pack. For hot pack, boil gently for 5 minutes then pack. Hot or Raw 10 10
Sources for additional canning instructions:
* Ball Blue Book, Edition 1, Ball Corporation, Muncie, IN, 1994.
* Kerr Home Canning and Freezing Book, Kerr Glass Manufacturing Corporation, Sand Springs, Oklahoma, 1982.
* The New Putting Food By, Third Edition, R. Hertzberg, B. Vaughn and J. Greene. The Stephen Greene Press, Brattleboro, Vermont, 1982.
* So Easy to Preserve, Third Edition, Cooperative Extension Service -- The University of Georgia, 1993.
Canning Glossary of Terms (A-L)
Acid foods - Foods which contain enough acid to result in a pH of 4.6 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 anti caking 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 caners. 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 4.6. The acidity in these foods is insufficient to prevent the growth of the bacterium Clostridium botulinum. Vegetables, some tomatoes, figs, all meats, fish, seafood’s, 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 4.6 or lower before processing in boiling water.
Microorganisms - Independent organisms of microscopic size, including bacteria, yeast, and mold. When alive in a suitable environment, they grow rapidly and may divide or reproduce every 10 to 30 minutes. Therefore, they reach high populations very quickly. Undesirable microorganisms cause disease and food spoilage. Microorganisms are
sometimes intentionally added to ferment foods, make antibiotics, and for other reasons.
Mold - A fungus-type microorganism whose growth on food is usually visible and colorful. Molds may grow on many foods, including acid foods like jams and jellies and canned fruits. Recommended heat processing and sealing practices prevent their growth on these foods.
Mycotoxins - Toxins produced by the growth of some molds on foods.
Open - Kettle canning A non-recommended canning method. Food is supposedly adequately heat processed in a covered kettle, and then filled hot and sealed in sterile jars. Foods canned this way have low vacuums or too much air, which permits rapid loss of quality in foods. Moreover these foods often spoil because they become recontaminated
while the jars are being filled.
Pasteurization - Heating of a specific food enough to destroy the most heat-resistant pathogenic or disease-causing microorganism known to be associated with that food.
pH - A measure of acidity or alkalinity. Values range from 0 to 14. A food is neutral when its pH is 7.0: lower values are increasingly more acidic; higher values are increasingly more alkaline.
Pickling - The practice of adding enough vinegar or lemon juice to a low-acid food to lower its pH to 4.6 or lower. Properly pickled foods may be safely heat processed in boiling water.
Pressure caner - A specifically designed metal kettle with a lockable lid used for heat processing low-acid food. These caners have jar racks, one or more safety devices, systems for exhausting air, and a way to measure or control pressure. Caners with 20- to 21-quart capacity are common. The minimum volume of caner that can be used is 16-quart capacity, which will contain 7 quart jars. Use of pressure saucepans with less than 16-quart capacities is not recommended.
Raw pack - The practice of filling jars with raw, unheated food. Acceptable for canning low-acid foods, but allows more rapid quality losses in acid foods heat processed in boiling water.
Spice bag - A close able fabric bag used to extract spice flavors in a pickling solution.
Style of pack - Form of canned food, such as whole, sliced, piece, juice, or sauce. The term may also be used to reveal whether food is filled raw or hot into jars.
Vacuum - The state of negative pressure. Reflects how thoroughly air is removed from within a jar of processed food--the higher the vacuum, the less air left in the jar.
Yeasts - A group of microorganisms which reproduce by budding. They are used in fermenting some foods and in leavening breads.