Family & Consumer Science
FREQUENTLY ASKED QUESTIONS IN HOME FOOD PRESERVATION

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Canning

MOST FREQUENTLY ASKED CANNING QUESTIONS return to top
General
Can food be recanned if the lid does not seal? Canned food can safely be recanned if the unsealed jar is discovered within 24 hours. To recan, remove the lid and check the jar sealing surface for tiny nicks. Change the jar if necssary, add a new treated lid and reprocess using the same processing time.
If canned foods have been frozen during storage, are they safe to eat? Freezing does not cause food spoilage unless the seal is damaged or the jar is broken. This often happens as the food expands during freezing. However, frozen foods may be less palatable than properly stored canned food. In an unheated storage place, protect canned foods by wrapping the jars in paper or covering them with a blanket.
If my recipe doesn't call for processing, do I need to do so? Many recipes passed down through the years or found in older cookbooks do not include instructions for processing. The foods are usually canned by the open kettle method, sealed and stored. Foods prepared in this manner present a serious health risk-particularly low acid foods. To minimize the risk of food spoilage, all high acid foods should be processed in a water bath canner or pressure canner and all low acid foods in a pressure canner.
Do I really need to leave a certain amount of head space in the jar? Yes, leaving the specified amount of head space in a jar is important to assure a vacuum seal. If too little head space is allowed the food may expand and bubble out when air is being forced out from under the lid during processing. The bubbling food may leave a deposit on the rim of the jar or the seal of the lid and prevent the jar from sealing properly. If too much head space is allowed, the food at the top is likely to discolor. Also, the jar may not seal properly because there will not be enough processing time to drive all the air out of the jar.
How long will canned food keep? Properly canned food stored in a cool, dry place will retain optimum eating quality for at least 1 year. Canned food stored in a warm place near hot pipes, a range, a furnace, or in indirect sunlight may lose some of its eating quality in a few weeks or months, depending on the temperature. Dampness may corrode cans or metal lids and cause leakage so the food will spoil.
Is it necessary to sterilize jars before canning? Jars do not need to be sterilized before canning if they will be filled with food and processed in a boiling water bath canner for 10 minutes or more or if they will be processed in a pressure canner. Jars that will be processed in a boiling water bath canner for less than 10 minutes need to be sterilized by boiling them in hot water for 10 minutes before they're filled.
Is it safe to process food in the oven? No. This can be dangerous because the temperature will vary according to the accuracy of oven regulators and circulation of heat. Dry heat is very slow in penetrating into jars of food. Also, jars explode easily in the oven.
Can two layers of jars be processed in a canner at one time? Yes, two layers can be processed at one time, in either the boiling water bath or pressure canner. Place a small wire rack between the layers so water or steam will circulate around each jar. Make certain that the water covers the top of the jars by 1 inch in a boiling water bath canner. The pressure canner should have 2 to 3 inches of water in the bottom.
Is it necessary to exhaust a pressure canner? Yes, it is very important to allow steam to escape for 10 minutes before closing the valve, or placing the weight on the vent. If the canner is not exhausted, the inside temperature may not correspond to the pressure on the gauge.
Should liquid lost during processing be replaced? No. Loss of liquid does not cause food to spoil, though the food above the liquid may darken.
Is it all right to reuse jar fittings (lids and bands)? Lids should not be used a second time since the sealing compound becomes indented by the first use, preventing another airtight seal. Screw bands may be reused unless they are badly rusted or the top edge is pried up which would prevent a proper seal.
Why is open kettle canning not recommended? In open kettle canning, food is cooked in an ordinary kettle, then packed into hot jars and sealed without processing. The temperatures obtained in open kettle canning are not high enough to destroy all spoilage and food poisoning organisms that may be in the food. Also, microorganisms can enter the food when it is transferred from the kettle to jar and cause spoilage.
Why do the undersides of metal lids sometimes discolor? Natural compounds in some foods, particularly acids, corrode metal and make a dark deposit on the underside of jar lids. This deposit on lids of sealed, properly processed canned foods is harmless.
What causes jars to break in a canner? Breakage can occur for several reasons: 1. Using commercial food jars rather than jars manufactured for home canning, 2. Using jars that have hairline cracks, 3. Putting jars directly on bottom of canner instead of on a rack, 4. Putting hot food in cold jars, or 5. Putting jars of raw or unheated food directly into boiling water in the canner, rather than into hot water (sudden change in temperature-too wide a margin between temperature of filled jars and water in canner before processing).
If I find mold growing inside a jar of canned food, can I just scrape it off and eat the food? Mold growth in foods can alter the pH of the food. In home canned products, this could mean that the high acid products could become low acid and therefore run the risk of botulism or other bacterial spoilage. Thus, any home canned product that shows signs of mold growth should be discarded. The exception to this is jellied products. In these the high sugar content would prevent the growth of Clostridium botulinum. In jellied products, remove any surface mold plus 1/2 inch of the good product underneath and then use the rest immediately. Jellied products with extensive mold should be discarded.
How can I remove scale or hard water film from canning jars? Soak jars for several hours in a solution containing 1 cup of vinegar and 1 gallon of water.

Vegetables and Fruits return to top
CSU Publications: Canning Tomatoes and Tomato Products, Canning Fruits, Canning Vegetables
Is it safe to can food without salt? Yes. Salt is used for flavor only and is not necessary to prevent spoilage. See our publication on-line, Food Preservation Without Sugar or Salt.
Is it safe to can fruits without sugar? Yes. Sugar is added to improve flavor, help stabilize color, and retain the shape of the fruit. It is not added as a preservative. See our publication on-line, Food Preservation Without Sugar or Salt.
Can fruits and vegetables be canned without heating if aspirin is used? No. Aspirin should not be used in canning. It cannot be relied on to prevent spoilage or to give satisfactory products. Adequate heat treatment is the only safe procedure.
Is it safe to can green beans in boiling water bath is vinegar is used? No. Recommended processing methods must be used to assure safety. Recommended processing times cannot be shortened if vinegar is used in canning fresh vegetables (this does not refer to pickled vegetables).
Should all vegetables be precooked before canning? For best quality, yes. However, some vegetables can be packed raw or cold into jars before being processed in the pressure canner.
What vegetables expand instead of shrink during processing? Corn, peas and lima beans are starchy and expand during processing. They should be packed loosely.
What causes corn to turn brown during processing? This occurs most often when too high a temperature is used causing caramelization of the sugar in the corn. It may also be caused by some minerals in the water used in canning.

Meats return to top
CSU Publications: Smoking Poultry Meats
Should giblets of chicken be canned in the same jar with chicken? No. Their flavor may permeate other pieces of chicken in the jar.
Is it safe to can meat and poultry without salt? Yes. Salt is used for flavor only and is not necessary for safe processing.
Why is it necessary to remove as much fat from meats as possible before canning? Any fat that gets on the rim of the canning jar can prevent an air tight seal. Excess fat in jars makes it easier for the fat to climb the sides of the jar and contaminate the seal.

MOST FREQUENTLY ASKED PICKLE QUESTIONS return to top
CSU Publications: Making Pickles, Making Pickle Peppers
Can I used flaked salt for pickling? Most recipes call for granulated pickling or canning salt. Flake salt varies in density and is not recommended for pickling.
When making quick process pickles, can I store any leftover pickling solution for future use? If the pickling solution is fresh and has not been used to make pickles, cover it and store it in the refrigerator for later use. If the pickling solution has been used, it can be stored in the refrigerator and reused in 1 or 2 days for barbecue sauce, cole slaw dressing or a marinade. If mold growth occurs, throw it out.
Why did the liquid in my dill pickles turn pink? Using over mature dill may cause this. If so, the product is still safe. However, yeast growth could also cause this. If yeast growth is evident, discard the pickles.
I don't have the type of dill my recipe calls for. How can I subsitute what I have? For each quart try 3 heads of fresh dill or 1 to 2 tablespoons dill seed (dill weed = 2T).
Can I use burpless cucumbers for pickling? Burpless cucumbers are not recommended for use in fermented pickles. This is because at their normal mature size, they produce a softening enzyme that causes the pickles to soften during fermentation. However, if smaller burpless cucumbers (those with small seeds) are used, they may be suitable for making fresh pack pickles. The skins on burpless cucumbers may be tough.
I have an old recipe that calls for adding a grape leaf to each jar of pickles. Why? Grape leaves contain a substance that inhibits the enzymes that make pickles soft. However, if you remove the blossom ends (the source of undesirable enzymes) you don't need to add grape leaves.
Why did the garlic cloves in my pickles turn green or bluish green? This reaction may be due to iron, tin or aluminum in your cooking pot, water or water pipes reacting with the pigments in the garlic. Or, the garlic may naturally have more bluish pigment and it is more evident after pickling. Immature bulbs should be cured 24 weeks at 70°F. The pickles are safe to eat.

MOST FREQUENTLY ASKED JELLIED FRUIT PRODUCTS QUESTIONS return to top
CSU Publication: Making Jellies
Why should cooked jelly be made in small batches? If a larger quantity of juice is used, it will be necessary to boil it longer thus causing loss of flavor, darkening of jelly, and toughening of jelly.
Should jelly be boiled slowly or rapidly? It should be boiled rapidly since long, slow boiling destroys the pectin in the fruit juice.
What do I do if there's mold on my jellied fruit product? If the mold is extensive, discard all of the product. If the mold is just slight on the surface, discard the mold and 1/2 inch of the good product underneath. Though mold growth can change the pH of products, the high sugar concentration would prevent any danger of botulism.
Why did my jellied fruit product ferment, and what do I do? Jellied fruit products may ferment because of yeast growth. This can occur if the product is improperly processed and sealed, or if the sugar content is too low. Fermented fruit products have a disagreeable taste. Discard them.

MOST FREQUENTLY ASKED FREEZING QUESTIONS return to top
General
Can frozen food be stored in refrigerator-freezer combinations? Refrigerator-freezer combinations can be used for storing frozen food if the freezer is a true freezer (will maintain 0°F or less) and not just a freezing compartment. A better quality product will be maintained at 0°F or less. If a freezing compartment is used, store food for only one to two weeks.
Is it necessary to leave head space in packages to be frozen? With the exception of vegetables that pack loosely, such as broccoli and asparagus, leave adequate head space between packed food and closure. This allows for expansion of food as it freezes.
At what temperature should the freezer be maintained? Freeze and store foods at 0°F or less.
How long will food remain frozen if the power goes off? Foods stay frozen longer if the freezer remains unopened, is full, is in a cool place and is well insulated. Usually food in a loaded freezer will stay frozen for two to four days, depending on its size. A half filled freezer will keep food frozen only about 24 hours. Cover the freezer with blankets, keeping them away from the compressor, to help hold the cold.
Can food be refrozen if it has thawed? Foods that have only partially thawed and still have ice crystals in the package can be safely refrozen, though quality will be poorer. Meat, fish, poultry, prepared foods, vegetables and fruits can be refrozen if the freezer temperature is 40°F or below and if color and odor are good. However, their quality will be lower.
What is freezer burn? It is dehydration or drying that occurs on the surface of a product if it is improperly wrapped. The food is safe to eat but poorer quality. To prevent freezer burn, the package must be free of air and sealed airtight.
Does freezing improve the quality of food? Freezing does not improve the quality of the product. Frozen food is only as good as the quality of the fresh food. So, select only high quality products at optimum maturity and freshness.
Does freezing kill germs? Freezing does not kill all germs (microorganisms) present in food, but it does prevent their growth and multiplication if the food is held at 0°F or less. When thawed, the surviving organisms can grow again.
How much food can be frozen at one time? Add only the amount that will freeze within 24 hours, which is usually two or three pounds of food per cubic foot of storage space. Overloading slows down the freezing rate. Also, foods that freeze too slowly may lose quality.
Will food spoil if it is held longer than the recommended storage time? No. The recommended storage time is the time in which food should be used to insure maximum quality. Food stored longer than recommended time is safe but will begin to have a decrease in flavor, color and texture.
How can you be sure that your freezer is at 0°F or less? Purchase a freezer thermometer (one that can withstand a wide range of temperatures), keep it in the freezer and check the temperature regularly.
Will it pay to buy a freezer? A freezer is usually more of a convenience than a saving. To make the best use of it, (1) keep the freezer full, (2) use and replace the food-don't just store it, and (3) use older food first.
Is a chest or upright freezer best? This depends on personal preference as well as available floor space. Generally speaking, the upright freezer is easier to organize and takes up less floor space. Chest freezers, however, are more economical to operate.

Packaging Materials return to top
What kind of packaging materials should be used for freezing? Packaging materials must be moisture-vapor resistant; durable and leak proof; not become brittle and crack at low temperatures; resistant to oil, grease or water; protect foods from absorption of off-flavors or odors; easy to seal; and easy to mark. Good freezing materials include rigid containers made of aluminum, glass, plastic, tin or heavily waxed cardboard; bags and sheets of moisture-vapor resistant wraps; and laminated papers made specially for freezing.
Can aluminum foil be used as a freezer wrap? Heavy duty aluminum foil can be used as a freezer wrap. Because it can be torn or punctured easily, it is wise to use an over wrap. Light weight (household) aluminum foil is not satisfactory for home freezing.
Is wax paper a suitable freezer wrap? No. Wax paper is not moisture-vapor resistant.
Can bread wrappers be used for freezing? No. Bread wrappers are not sufficiently moisture-vapor resistant to be used for freezing. A freezer weight polyethylene bag should be used.
Can zip-type bags be used for freezing? Yes, if they have been designed for and their box marked for freezer use.
Can milk or cottage cheese cartons be used for freezing foods? Cardboard cartons for cottage cheese, ice cream or milk are not sufficiently moisture-vapor resistant to be suitable for long term freezer storage.
Can glass jars be used for freezing? Regular glass jars break easily at freezer temperatures. If using glass jars, choose wide mouth dual purpose jars made for freezing and canning; these jars have been tempered to withstand extremes in temperatures. If standard canning jars (those with narrow mouths) are used, leave extra head space in liquid packs (3 inch for pints; 1 inches for quarts) to allow for expansion of food during freezing and completely thaw food before removing it. Do not use regular canning jars for foods packed in water.
Fruits return to top
CSU Publication: Freezing Fruits
Is it safe to freeze fruits without sugar? Yes; sugar is not used as a preservative but only to maintain flavor, color and texture.
Can artificial sweeteners be used in place of sugar for freezing fruits? Sugar substitutes can be used in place of sugar. Labels on the products give the equivalents to a standard amount of sugar. Follow the directions to determine the amount of sweetener needed. Artificial sweeteners give a sweet flavor but do not furnish beneficial effects of sugar, like thickness of syrup and color protection.
How do you prevent fruit from turning brown during freezing? There are several ways to prevent darkening of fruit; use pure ascorbic acid or ascorbic acid mixtures. Citric acid or lemon juice may sometimes be used but are not as effective as ascorbic acid. Some fruits which are to be cooked before serving may also be steamed to prevent browning.
What are frozen fruits sometimes softwhen thawed? If fruits are frozen slowly, large ice crystals form and rupture cell walls causing a soft mushy product. For best results, quick freeze at -10°F and serve just as ice crystals are disappearing.
Vegetables return to top
CSU Publications: Freezing Vegetables
What is blanching? Heating or scalding the vegetables in boiling water or steam for a short period of time.
Is it recommended to blanch vegetables before freezing? Yes. Blanching slows or stops the action of enzymes which cause loss of flavor, color and texture. Blanching cleanses the surface of dirt and organisms, brightens the color and helps retard loss of vitamins. Blanching also wilts or softens vegetables and makes them easier to pack.
How do you blanch vegetables? Use a wire blanching basket and cover, or fit a wire basket into a large kettle with fitted lid. Use one gallon water per pound of prepared vegetable. Put vegetable in blanching basket and lower it into vigorously boiling water. Place lid on blancher and start processing time immediately. Keep heat high for time given in directions for vegetables you are freezing.
Why is it necessary to cool vegetables after blanching? Vegetables should be cooled quickly and thoroughly after blanching to stop the cooking process. Otherwise, vegetables will be overcooked with loss of flavor, color, vitamins and minerals.
What causes frost or ice crystals to appear on the surface of frozen vegetables such as broccoli? Inadequate draining of vegetables before freezing, slow freezing or fluctuation of storage temperatures above 0°F may cause undesirable formation of large and excessive ice crystals. This can affect the texture as well as appearance of frozen vegetables.
Can I blanch in my microwave oven? Microwave blanching may not be effective, since research has shown that some enzymes may not be inactivated. This could result in off flavors and loss of texture and color. Those wishing to run the risk of low quality vegetables by microwave blanching, should be sure to work in small quantities, using the directions for their specific microwave oven. Microwave blanching will not save time or energy.
Can vegetables be fully cooked before freezing? Some fully cooked vegetables, such as baked beans and candied sweet potatoes, maintain high quality for many months when frozen. Most fully cooked vegetables, however, have less desirable color, aroma and flavor when reheated. Loss of flavor may be retarded by covering the vegetable with cooking liquid, meat broth or cream sauce.
Does it matter how long vegetables are blanched? Blanching time is crucial and varies with the vegetables and size. Under-blanching stimulates the activity of enzymes and is worse than no blanching. Over blanching causes loss of color, flavor, vitamins and minerals.
Are frozen vegetables safe to eat is they are not blanched? Yes. They are safe to eat, but the quality (color, flavor and texture) will be poorer than that of vegetables which have been blanched. Blanching slows or stops the action of enzymes which cause loss of flavor, color and texture.
How can you prevent corn-on-the-cob from tasting "cabby"? After blanching ears for the recommended time, chill immediately with ice water until the cobs are completely cold. Partially thaw the ears of corn before cooking.
Should frozen vegetables be thawed before cooking? For most vegetables, no. You get a fresher tasting product if it has not been thawed. Exceptions are corn-on-the-cob and leafy greens which cook more evenly if partially thawed first.
Is it necessary to wash peas and lima beans before shelling? Any vegetable should be washed before shelling to remove any foreign material such as dirt, insects, leaves, etc.
Animal Products return to top
Is it necessary to thaw meat or fish before cooking? No, meat and fish can be cooked from the frozen stage if extra cooking time is allowed. The amount of time will depend on the size and shape of the cut. Large frozen roasts can take as much as 1 1/2 times as long to cook as unfrozen cuts of the same weight and shape. Small roasts and thin cuts such as steaks and chops require less time.
Can meat and poultry be thawed in the conventional oven? Meat and poultry should never be thawed in the conventional oven or at room temperature. There is greater danger of bacterial growth and food spoilage for food thawed at room temperature. Thaw meat and poultry in the refrigerator in the original wrappings. To speed thawing, loosen the wrapping. For a quicker method, immerse meat or poultry in a watertight bag into cold water. Thaw until it is pliable. Meat and poultry can also be thawed quickly and safely in the microwave oven. Because microwave ovens vary, check your manufacturer's instructions for information on how to safely thaw in your microwave oven. Frozen meat and poultry can also be cooked without thawing.
Why is it important to chill meat or poultry before freezing? Slaughtered meat and poultry should be put under refrigeration (32°-36°F) immediately to remove animal heat from the carcass. Prompt and thorough chilling is important to reduce bacterial growth and decrease the action of enzymes which can lower the quality. Bone souring in beef and pork may also occur if carcasses are not properly chilled. Chill pork, lamb or veal 24 hours; beef 5 to 7 days.
Can stuffed turkey be frozen? Stuffing should be frozen separately from the turkey. With any food, the time needed for freezing to take place in the center of the item is the critical factor.
MOST FREQUENTLY ASKED DRYING QUESTIONS return to top
CSU Publications: Drying Vegetables, Drying Fruits, Leathers and Jerkies, Growing and Preserving Herbs
How can I tell when fruit leather is dry? Touch it; it shouldn't be sticky. If it peels from the plastic and maintains its shape, it is dry.
My banana chips don't taste like the ones in the stores. What can I do? There are a variety of banana chips available. Read the ingredients on the label. Some bananas are dipped in honey, some are dipped in granulated sugar, brown sugar or flavored gelatin. Be sure bananas are ripe. Some commercial banana chips have been treated to make them crisp. This can't be done in the home.
Where can I buy sodium bisulfite? Food grade sodium bisulfite is available from drugstores or hobby stores that have wine making ingredients. If you are unable to find a source, ask your county Extension agent.
The fruit sticks to the trays. How can I prevent this? Fruits or thinly sliced vegetables may stick to plastic trays. To help prevent this, spray trays with vegetable cooking spray. Also, gently lift food with a spatula after one hour of drying.
What are other uses of a food dehydrator? Besides being used during peak season to preserve food, a food dehydrator can be used for proofing breads, making yogurt or cheese, drying seeds, curing nuts, decrystallizing honey and drying crafts.
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