Freezing is one of the simplest and least time-consuming ways to preserve foods at home.
Freezing does not sterilize food. The extreme cold simply retards growth of micro-organisms and slows down changes that affect quality or cause spoilage in food. Properly frozen fruits retain much of their fresh flavor and nutritive value. Their texture may be somewhat softer than fresh fruit.
Selecting Freezing Containers
To prevent evaporation and retain the highest quality in frozen foods, packaging materials should be moisture and vapor-proof. Glass jars and metal and rigid plastic containers meet these criteria. Many packaging materials designed for frozen food, including most plastic bags and heavily waxed cartons, are not moisture and vapor-proof, but can be used satisfactorily
Container shape and size is another consideration. Food can be removed easily before thawing if containers have straight sides or sides that flare out. Square or rectangular flat-sided containers waste less freezer space than round containers.
Selecting and Preparing Fruit
Berries and cherries are best frozen soon after harvest. Peaches, apricots, plums, apples and pineapples may need to be held a short time after harvest to fully ripen before freezing.
Sort, wash and drain fruits carefully, discarding parts that are green or of poor quality. Do not allow fruits to soak in wash water. This will cause them to lose nutrients and flavor. Prepare fruits as they will be used: stemmed, pitted, peeled and sliced. It is best to prepare enough fruit for only a few containers at a time, especially for fruits that darken rapidly.
Do not let galvanized equipment come into direct contact with fruit. The acid in the fruit dissolves zinc, which is poisonous. Also be wary of iron utensils or chipped enamel ware, as this can result I foods with a metallic flavor.
Some fruits need pretreatment to prevent darkening. There are several anti-darkening treatments that may be used.
Ascorbic acid (vitamin C) is effective in preserving color and flavor and adds nutritive value. Ascorbic acid is available from pharmacies or where canning supplies are sold. To use, dissolve crystalline or powdered forms in a little cold water. When using tablets, crush first so they dissolve easily.
For syrup packs, dissolve 1/2 teaspoon crystalline ascorbic acid or 1,500 milligrams vitamin C in each quart of cold syrup shortly before using. Stir it in gently so as not to stir in air. Refrigerate until ready to use.
For sugar and unsweetened packs, sprinkle 1/4 teaspoon crystalline ascorbic acid dissolved in 1/4 cup of cold water over each quart of fruit just before adding sugar, if used. In fruit juices, add 1/4 teaspoon ascorbic acid directly to each quart of juice. Stir only enough to dissolve ascorbic acid.
In crushed fruits and fruit purees, add 1/4 teaspoon crystalline ascorbic acid dissolved in 1/4 cup of cold water to each quart of the fruit preparation and mix.
Ascorbic acid mixtures. Special commercial anti-darkening preparations (ascorbic acid mixed with sugar or with sugar and citric acid) also may be used to retard darkening. Follow manufacturer’s directions.
Citric acid or lemon juice may be used for treating some fruits but are not as effective as ascorbic acid. Dissolve 1/4 teaspoon crystalline citric acid or 3 tablespoons of lemon juice in each quart of cold water. Dip the prepared fruit in the solution and leave for one to two minutes. Drain and pack with sugar, syrup, water or fruit juice. One gallon of citric acid or lemon juice solution treats about 1 bushel of fruit.
Methods of Packing Fruits
There are several ways to pack fruit for freezing. Fruits packed in syrup generally are best for most cooking processes. Small whole fruits, such as berries, packed on trays are good for salads or garnishes. (See Table 1 for sugar syrup recipes.)
Syrup pack. A 30-percent syrup (1 3/4 cup sugar per 4 cups water) is recommended for most fruits. Lighter syrups are lower in caloric content and especially desirable for mild-flavored fruits, such as melons. Heavier syrups may be needed for very sour fruits. Allow 1/2 to 2/3 cup of syrup for each pint of fruit.
To pack fruit in syrup, pour 1/2 cup cold syrup into each container. Add fruit and cover with additional syrup, leaving sufficient headspace at top of container. Allow 1/2 inch of headspace for wide-top pints, 1 inch for wide-top quarts, 3/4 inch for narrow-top pints and 1 1/2 inches for narrow-top quarts. Allow 1 1/2 inches of headspace for juices packed in narrow-top containers, regardless of size.
Sugar pack. Place prepared, cut fruit in a bowl or shallow pan. Sprinkle sugar over the fruit. Mix gently with a large spoon until the sugar dissolves and juice is drawn out. Pack in containers, allowing the headspace recommended for syrup-packed fruit.
Unsweetened pack. Pack prepared fruit into containers without liquid or sweetening, or cover with water containing 1 teaspoon ascorbic acid per quart of water. Nonnutritive sweeteners may be added to the water to provide sweetness. Fruit also may be sweetened at the time of serving.
Soft fruits may be packed in their own juice by crushing the fruit lightly to produce juice. For firmer fruits, puree a small amount of the fruit to obtain enough juice to cover.
Pack foods tightly to cut down on the amount of air in the package. Press out as much air as possible for fruits packed in bags. Allow 1/2 inch of headspace for fruits packed without juice or liquid. For fruits packed in juice or liquid, allow headspace recommended for syrup packs.
Tray pack. Spread small, whole fruits, such as strawberries, raspberries, blueberries and sweet cherries, in a single layer on shallow trays and freeze. Remove and quickly package in labeled freezer bags or containers removing as much air as possible from containers and allowing no headspace. Seal and return to freezer.
Sealing, Labeling and Storing
Before closing, make sure sealing edges are free of moisture or food. Place a small piece of crumpled parchment paper or other water-resistant wrapping material between the fruit and the lid of juice- or liquid-packed fruits to help keep the fruit submerged in the liquid. Close and carefully seal the container. Label packages plainly. Include name of food, date and type of pack.
Freeze packaged fruits as quickly as possible at 0 degrees F or below. For quickest freezing, place packages against freezing plates or coils in single layers. Freeze only as much at one time as will freeze within 24 hours.
Most fruits maintain high quality for eight to 12 months at 0 degrees or below. Citrus fruits and citrus juices may be stored for four to six months. Unsweetened fruits lose quality faster than those packed in sugar or syrup. Longer storage will not make the food unfit for use, but may impair its quality. Post a list of the frozen foods with freezing dates near the freezer, and check the packages off the list as they are removed.
Source: Colorado Cooperative Extension
Sandra R. Cain is the Extension agent for Family and Consumer Sciences in Bladen County.