Freezing is one of the simplest and least time-consuming methods of food preservation. Under optimal conditions, freezing is the best form of food preservation in terms of retaining nutrients, flavor, and texture.
Freezing does not kill most microorganisms (except trichinae and fish parasites); it just puts them to sleep. Therefore, it is important to handle foods safely prior to freezing and when defrosting. Always wash your hands, surfaces, cutting boards, and knives before preparing foods for freezing.
For best quality, follow directions carefully. Color, flavor, and nutritive value can be affected by the freshness of the produce selected, method of preparation and packaging, and conditions of freezing.
(See Freezing fruits, tables 1 and 2 for specific directions.)
Any fruit can be frozen without sugar. However, the texture may be softer than that of fruit frozen with sugar.
Fruits such as berries, cherries, and grapes may be frozen in a single layer on cookie sheets before packing in containers. This prevents them from sticking together. Serve them frozen as snacks or thaw and use as a topping for salads or desserts.
If desired, a water pack (without sugar) can be used for fruit such as peaches. Fruit juice (either extracted from the fruit or purchased) can also be used. Orange, grape, apple, and berry juices are suitable.
Fruits that will be served uncooked are often packed in a sugar syrup. The syrup may be prepared from either cane or beet sugar. If desired, part of the sugar may be replaced by honey. Select the strength of syrup that will give the desired flavor. (This will depend on the sweetness of the fruit, personal preference, and intended use.) Allow about ⅔ cup of syrup for each pint of fruit and 1⅓ cups for each quart of fruit. Dissolve sugar in hot or cold water. If hot, cool before using. See Syrup Strength Table for preparing light, medium, and heavy syrups.
Juicy fruits and those that will be used for pies or other cooked products are often packed in sugar. Use about 1 cup of sugar for each 2 to 3 pounds of fruit. Sugar and fruit should be gently but thoroughly mixed together until the sugar has dissolved in the juice.
Sugar substitutes may be used in any of the unsweetened packs. They can be added prior to freezing or just before serving. Follow manufacturer instructions for the amount to use. Artificial sweeteners give a sweet flavor, but do not provide the benefits that sugar provides in freezing (such as improved texture, color, and thickness of syrup).
When freezing light-colored fruit, ascorbic acid can be added to inhibit browning. Ascorbic acid in powder or crystal form is often available at pharmacies and health food stores. Ascorbic acid tablets (vitamin C) can also be used. Crush finely before use. (Three crushed 500-milligram vitamin C tablets equal ½ teaspoon of ascorbic acid.)
For syrup or liquid packs, add ½ teaspoon powdered or crushed ascorbic acid to each quart (4 cups) of cold syrup.
For sugar or sugarless (dry) packs, dissolve ½ teaspoon ascorbic acid in 3 tablespoons cold water and sprinkle over 4 cups of fruit just before adding sugar.
Follow manufacturer’s directions for commercial antidarkening products. Ascorbic acid is the main ingredient in commercial mixtures available in most supermarkets.
A variety of fruit juices can be prepared, including cherry, grape, grapefruit, plum, raspberry, and strawberry. The procedure is similar for each.
Tomato juice can be extracted by simmering quarters or eighths for 5 to 10 minutes. (Skipping this step causes the juice to separate.) Then press through a sieve or food mill. Season with salt, if desired. Pour into containers and freeze.
(See Freezing vegetables, tables 1-5, for specific directions.)
Food must be packed in suitable containers for freezing. These containers should be durable, easy to handle, and moisture and vapor resistant. They should also protect foods from absorbing other flavors and colors. Select containers that will pack well in the freezer. Smaller containers are best since food will freeze faster and more evenly. Fruits and vegetables should not be frozen in anything larger than a half-gallon.
Acceptable containers include:
Pack foods tightly into containers. Allow ample headspace between the packed food and the lid to allow room for expansion during freezing. See table below.
To keep fruit covered with liquid, put a crumpled piece of freezer wrap or waxed paper between the fruit and the lid. This will keep the surface from darkening and drying out.
When food is packed in freezer bags, squeeze out as much air as possible. To remove air, twisting freezer bags can help. There are also commercial products that help draw out air. Seal the package well.
Label containers with name of product, type of pack (for fruit), and date.
Freeze fruits and vegetables as soon as possible after they are packed. If there will be a delay before freezing, keep packages in the refrigerator.
Foods that freeze too slowly may lose quality or spoil. Only put the amount of unfrozen food into a home freezer that will freeze within 24 hours. Usually this will be about 2 or 3 pounds of food for each cubic foot of freezer capacity. For fastest freezing, place packages in a single layer against freezing plates or coils. Leave a little space between them so that air can circulate freely. Make sure the packages are completely dry so they don’t freeze to the freezer. Stack after frozen. See Headspace Table to determine how much headspace to allow for different size containers.
After freezing, packages may be stored close together. Store them at 0°F (-18°C) or below. Foods lose quality and nutritive value much faster at higher temperatures. Use a freezer thermometer to monitor the temperature.
Most fruits and vegetables maintain high quality for 8 to 12 months. (Unsweetened fruits lose quality faster than those packed in sugar or syrup.) Storage for longer periods will affect the quality of the frozen foods, but they will be safe to eat.
Keeping a freezer inventory and dating packages will help to rotate the supply.
Occasionally a home freezer stops running. The length of time food will stay frozen depends on the amount of food in the freezer and the temperature of the food. A full load of food will stay frozen for up to 2 days if the freezer is not opened. Dry ice can be used to keep foods frozen longer. If the power will be off for a long period of time, food should be transferred to a working freezer.
It is safe to refreeze fruits and vegetables that still contain ice crystals. For best quality, refreeze food in small quantities.
If the temperature has warmed above 40°F (5°C), foods may not be safe for refreezing. Check your freezer thermometer to determine the temperature.
Do not eat thawed vegetables that are above 40°F. The low acidity of vegetables makes it possible for harmful bacteria to grow. Unsafe products may not show obvious signs of spoilage.
For information about the safety of specific foods, call your local Extension office. Be prepared to give the “history” of the food (length of time that the power was off and temperature of the food before the freezer began to run again).