Can Foods Safely—Avoid “Can Grenades”!

Pamela Schmutz
Home & Garden Information Center

If you're just learning to preserve foods, watch out for "can grenades!" A first-time canner called us to say that when he opened his jars of pickles, liquid spurt out everywhere making a mess. What went wrong? Some bacteria flourishing in preserved foods create gas as they grow. The gas creates pressure and when the jar is opened the gas bursts out forcing out the liquid. Sometimes the jars will even explode before the lid is opened! It’s a sure sign that the food is spoiled. Some poisons that grow in home canned foods do not even show any signs that the food would be deadly to eat. That is why it is so important to follow tested recipes exactly. If you don't, you could be putting up a pantry full of potential poison. Every year, families suffer bouts of food poisoning because of improperly preserved fruits and vegetables.

Whether you have been canning for years, or this is the first time, follow tested recipes exactly to make sure you have a safe product. Foods MUST be processed properly to kill bacteria that cause foodborne illness. Simply putting food in jars and covering with a hot liquid (like our caller did) is not safe even if the lids seal. High acid foods like fruits and jams MUST be processed in a water bath canner to prevent molds and yeasts from spoiling them. Low acid foods, such as vegetables and meats, MUST be processed in a pressure canner to prevent the formation of the deadly botulism toxin. Vacuum packaging foods is not a substitute for proper processing of foods. Perishable foods that are vacuum packaged must be properly refrigerated or frozen.

If you have room in your freezer, freezing is a good choice and is an easy and safe way to preserve apples, pumpkins and other fall foods. For the best results, HGIC 3063, Freezing Fruits & Vegetables gives the times for blanching fresh vegetables and instructions for adding sugar or syrups to fruits. Drying foods is also a good option, although in highly humid climates like South Carolina, a dehydrator is usually needed. HGIC 3084, Drying Fruits and HGIC 3085, Drying Vegetables give specific instructions for drying different fruits and vegetables. For information on using a water bath canner or a pressure canner to preserve your foods by canning, see HGIC 3040, Canning Foods at Home.

Enjoy the recipes included here, or for more ideas look through the Food Preservation topics on this web site. To speak to a food safety specialist, South Carolina residents may call the toll-free number 1-888-656-9988 Monday through Friday from 9am to 1pm.

Freezing Apples
A sugar or dry pack is good for pie making. Select full-flavored apples that are crisp and firm, not mealy in texture. Wash, peel and core. Slice medium apples into twelfths, large ones into sixteenths.

Sugar Pack: To prevent darkening, dissolve ½ teaspoon (1500 mg) ascorbic acid in 3 tablespoons water. Sprinkle over the fruit. Or, apple slices can be steam blanched for 1½ to 2 minutes. Mix ½ cup sugar with 1 quart (1¼ pounds) of fruit. Pack apples into containers and press fruit down. Seal and freeze.

Dry Pack: Follow the directions for sugar pack, omitting the sugar. Apple slices treated to prevent darkening can also be frozen first on a tray and then packed into containers as soon as they are frozen.

Freezing Pumpkin
Select full-colored mature pumpkin with fine texture. Wash, cut into cooking-size sections and remove seeds. Cook until soft in boiling water, in steam, in a pressure cooker or in an oven. Remove pulp from rind and mash. To cool, place pan containing pumpkin in cold water and stir occasionally. Package, leaving ½-inch headspace. Seal and freeze.

Canning Applesauce
Select apples that are sweet, juicy and crisp. For a tart flavor, add 1 to 2 pounds of tart apples to each 3 pounds of sweeter fruit.

Hot Pack: Wash, peel and core apples. To prevent darkening, slice apples into a solution of 1 teaspoon or 3000 mg ascorbic acid (Vitamin C) and 1 gallon of water. If using tablets, crush thoroughly before adding the water. Or use a commercial ascorbic acid mixture such as Fruit Fresh ™ according to label instructions. Drain and discard the solution, and put the apple slices into an 8 to 10-quart pot. Add ½ cup water. Stirring occasionally to prevent burning, heat quickly and cook until tender (5 to 20 minutes, depending on maturity and variety). Press through a sieve or food mill, if desired. If you prefer chuck-style sauce, omit the pressing step. If desired, add 2 tablespoons sugar per quart of sauce. Taste and add more, if preferred. Reheat sauce to boiling. Pack into hot jars, leaving ½-inch headspace. Remove air bubbles. Wipe jar rims. Adjust lids. Process in a boiling water bath canner for 15 minutes for pints and 20 minutes for quarts.

Canning Pumpkin
Pumpkins should have a hard rind and stringless, mature pulp. They should be ideal for cooking fresh. Small pumpkins (sugar or pie pumpkins) make better products.

Hot Pack: Wash pumpkin and remove seeds. Cut into 1-inch slices and peel. Cut flesh into 1-inch cubes. Add to a saucepot of boiling water, boil 2 minutes. Caution: Do not mash or purée. Pack hot cubes into hot jars, leaving 1-inch headspace. Fill jar to 1 inch from top with boiling hot cooking liquid. Remove air bubbles. Wipe jar rims. Adjust lids and process in a dial-gauge pressure canner at 11 pounds pressure or in a weighted-gauge pressure canner at 10 pounds pressure. Process pints for 55 minutes or quarts for 90 minutes.

Drying Apples
Peel and core, cut into slices or rings about ⅛-inch thick. Apples must be pretreated to prevent them from darkening during the drying process. Soaking slices in an ascorbic acid (vitamin C) solution to prevent fruit browning is adequate for short-term storage. For longer storage, see HGIC3084, Drying Fruits for other methods. Ascorbic acid (vitamin C) is available in the powdered or tablet form from drugstores or grocery stores. One teaspoon of powdered ascorbic acid is equal to 3000 mg of ascorbic acid in tablet form.

Pretreatment: Mix 1 teaspoon of powdered ascorbic acid (or 3000 mg ascorbic acid tablets, crushed) in 2 cups water. Place the fruit in the solution for 3 to 5 minutes. Remove fruit, drain well and place on dryer trays. After this solution is used twice, add more ascorbic acid.

Drying: Dry in a dehydrator at 140 ºF for 6 to 12 hours depending on desired crispness. To test for dryness, cut several cooled pieces in half. There should be no visible moisture and you should not be able to squeeze any moisture from the fruit. If a piece is folded in half, it should not stick to itself. Cool fruit 30 to 60 minutes before packaging. Avoid packaging warm food that could lead to sweating and moisture buildup. However, waiting too long to package could allow moisture to re-enter food from the air.

Conditioning: Pack the cooled apple slices loosely in plastic or glass jars. Seal the containers and let them stand for 7 to 10 days. The excess moisture in some pieces will be absorbed by the drier pieces. Shake the jars daily to separate the piece and check the moisture condensation. If condensation develops in the jar, return the fruit to the dehydrator for more drying.

Packaging: Pack fruit into clean, dry, insect-proof containers as tightly as possible without crushing. Glass jars are ideal for storing dried fruits. Pack fruit in amounts that will be used in a recipe. Every time a package is reopened, the food is exposed to air and moisture that lower the quality of the food. Store dried fruits in a cool, dry, dark pantry. Dried fruits can be stored for one year at 60 ºF, six months at 80 ºF. Check dried fruits regularly to see if they are still dry. Fruits affected by moisture, but not spoiled, should be used immediately or redried or repackaged. Moldy fruits should be discarded.

Drying Pumpkin Seeds
Pumpkin does not give a good product when dried, but the seeds may be dried and roasted for a delicious and nutritious snack.

To dry: Carefully wash pumpkin seeds to remove the clinging fibrous pumpkin tissue. Seeds can be dried until crisp in the sun, in a dehydrator at 115 to 120 ºF for 1 to 2 hours, or in an oven on warm for 3 to 4 hours. Stir frequently to avoid scorching.

To roast: Toss dried pumpkin seeds with oil (1 teaspoon per cup of seeds). Salt or season to taste. Roast in a preheated oven at 250 ºF for 10 to 15 minutes.

Source: Recipes are from The University of Georgia Cooperative Extension Service. So Easy to Preserve. Revised by Elizabeth Andress and Judy Harrison (2006).

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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.