Acid foods (all fruits except unacidified figs) can be safely processed in a water bath canner. Acidified tomatoes and figs can also be safely processed in a water bath canner. Microorganisms in or on acid foods are easily killed at 212 degrees F (the temperature of boiling water). Low-acid foods (vegetables and tomatoes and figs that are not acidified) must be processed in a pressure canner. The bacteria that produces botulinum toxin cannot grow in acid foods but can grow in low acid foods. These bacteria (Clostridium botulinum) have spores that survive hours of boiling water temperature. However, these spores are destroyed within a reasonable time at 240oF (the temperature reached inside a pressure canner set at 10 pounds pressure).
If low-acid food is processed in a water bath canner, botulinum spores on the food will survive. In the absence of air, a condition found inside a jar after processing, the spores become living bacteria. As the bacteria grow, they form toxin. Eating even a drop of this potent toxin can be fatal to humans and animals. Over 70% of the cases of botulism have been caused by low-acid foods that were improperly canned at home.
To make sure your home canned foods are safe, carefully follow the canning instructions in this bulletin. Process acid foods in a water bath canner and low-acid foods in a pressure canner. Never process any foods in a conventional oven, microwave oven, steamer or dishwasher, as these methods do not kill microorganisms that cause food spoilage and/or foodborne illness.
Canning jars. Use only standard canning jars (also called Mason jars) with the manufacturer's name printed on the side. These jars can withstand the temperature extremes of canning. And, the sealing edge is smooth and flat so lids will seal properly.
Never use commercial jars, such as mayonnaise and pickle jars, for home canning. These jars are not very resistant to temperature extremes; they break easily. Also, lids may not seal on these jars because their sealing edge may be rounded rather than flat. Finally, the neck of the jar may be so short that the screw band will not hold the lid firmly in place during processing.
Canning jars must be in perfect condition. Check all jars, new and used, for hairline cracks, chips or nicks on the sealing edge. Such defects can result in breakage or failure to seal.
Canning lids. The only safe way to seal a canning jar is with a two-piece canning lid. The set consists of a flat metal lid and a screw band. The lid has a sealing compound around the edge and is enameled on the under side to prevent food from reacting with the metal. The screw band holds the lid in place during processing. A vacuum seal forms during cooling, after the jar is removed from the canner. Screw bands that are in good condition may be reused, but always use new lids. Do not use screw bands that are bent or badly rusted.
Two types of canners. Use a water bath canner to process acid foods. A water bath canner is a large deep kettle that has a cover and a rack to hold jars. You can also use a big, covered pot that is deep enough to allow water to extend 1 to 2 inches over the tops of the jars with enough room for the water to boil briskly. Also add a rack to keep the jars off the bottom of the pot.
Use a pressure canner to process low acid foods. A pressure canner is a deep, heavy kettle that has a rack on the bottom for jars to stand on. It also has a tight-fitting lid with a gasket, and a pressure gauge. The gasket keeps steam from leaking out around the cover. If the gasket is worn, stretched, or hardened, replace it. There are two types of pressure measuring gauges, dial gauge and weighted gauge.
A dial gauge has a needle that moves along a numbered scale to indicate the pressure inside the canner. Each year check the dial gauge, old or new, for accuracy and during the canning season if heavily used. Call your extension agent, Family and Consumer Sciences, to find out where testing can be done.
A weighted gauge fits over the air vent tube. It permits pressure in the canner to rise to the desired point and then releases excess steam by "jiggling" or "rocking" to keep the pressure from going higher. Weighted gauges do not need testing for accuracy, but they do need to be kept clean. Check the vent tube to be sure it hasn't been bent or damaged during use.
Thoroughly wash fruits and vegetables before canning even if they will be peeled. Garden soil contains bacteria. NOTE: Potatoes must be peeled before canning. Potato skins contain a high bacteria count increasing the chance of botulinum toxin formation.
Wash by scrubbing with a vegetable brush and rinsing thoroughly. Or, if more practical, soak in water for several minutes. Lift out of the water so the soil that has been washed off won't settle back on the food. Peel, pit, and/or slice only as much food as you can process at one time.
Some fruits and vegetables (apples, apricots, nectarines, peaches, pears and potatoes) darken when cut. To prevent darkening, keep raw, prepared produce in a solution of 1 teaspoon ascorbic acid to one gallon of cold water. Check among the canners' supplies in the supermarket to get this product.
For either packing method, pack acid foods including acidified tomatoes and acidified figs to within 1/2 inch of the top of the jar. Low acid foods to within 1 inch of the top of the jar.
After food is packed into jars, wipe the jar rims clean. Put on the lid with the sealing compound next to the jar rim. Screw the band down firmly so that it is hand-tight. Do not use a jar wrench to tighten screw bands. There must be enough "give" for air to escape from the jars during processing. Process food promptly after packing it into jars and adjusting lids. Processing times are given for pints and quarts. If you are using half pint jars, use processing times for pints. For one-and-one-half pint jars, use processing times for quarts. Fruit juices are the only product that may be canned in half-gallon jars.
To determine your altitude, contact the North Carolina Geological Survey Office. Their address is: 512 North Salisbury Street, P.O. Box 27687, Raleigh, NC 27611. Their telephone number is 919-733-2423. After determining your altitude, your local extension center can help you to determine changes you need to make to your canning instructions.
Here are some pointers for using a pressure canner:
If you find an unsealed jar, do one of the following:
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.
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.
|Water Bath Process||Water Bath Process|
|PACK STYLE||Pints (minutes)||Quarts (minutes)/TH>|
|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.
|Pressure Process||Pressure Process|
|PACK STYLE||Pints (minutes)||Quarts (minutes)/TH>|
|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.
|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.
|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:
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