How to Prepare FRUITS and VEGETABLES for FREEZING

With suggestions for choosing suitable varieties - - -

Circular 602

University of Illinois

College of Agriculture

Extension Service in Agriculture and Home Economics

Contents

Forewords
Selecting Fruits and Vegetables
Blanching Vegetables According to Directions
Using Sugar or Sugar Sirup with Fruits
Packaging and Freezing
Preparing Frozen Foods for Serving
Suitability of Some Varieties
Table 1 -- VEGETABLES: How to Prepare for Freezer Storage
Table 2 -- FRUITS: How to Prepare and Pack for Freezer Storage
Table 3 -- Directions for Cooking Frozen Vegetrables

Start with fruits and vegetables of high quality.

Sort them carefully and make sure they are clean.

Process quickly according to tested directions.

Pack and seal in air-tight, leak-proof containers.

Place containers in the freezing unit immediately, or take to the locker as soon as possible.

Store at 0 F. or lower.

Remember that speedy, careful, efficient handling of high-quality fruits and vegetables is essential.

How to Prepare Fruits and Vegetables for Freezing

With Suggestions for Choosing Suitable Varieties

FREEZING, when properly done, is a most satisfactory method of preserving many fruits and vegetables. More of the original flavor, color, texture, and nutritive value is usually retained during freezing than when these foods are preserved in any other way.

Freezing does not, however, add anything to the original qualities of fresh fruits and vegetables. if, therefore, these foods are to be of highest quality after they are frozen, they must be of highest quality in their fresh state, and well-tested ways of preparing them for freezing must be carefully followed.

SELECTING FRUITS AND VEGETABLES

Choose only the very best quality

Select fruits and vegetables that have been grown under favorable weather and soil conditions. Remember that freezing does not improve these foods; in fact, undesirable characteristics are likely to be magnified. Seeds in berries and woodiness in asparagus and green beans are more noticeable after these vegetables have been frozen and held in freezer storage than they were before. Almost vegetables and certain fruits should be prepared for freezing as soon after picking as possible. lf they are held after harvesting, they usually lose some of their flavor and nutritive value.

Use fruits and vegetables suitably mature

The maturity of fruits and vegetables to be frozen is extremely important in determining the quality of the product. They should be picked at the stage when they are best for eating. Avoid over mature or starchy corn and peas. Select young and tender snap beans which have been picked before the pods have grown to more than two-thirds full size. Do not use hard or oversoft fruit. Fruit ripened on the tree, bush, or plant and prepared immediately for freezing is usually better than fruit picked at a less mature stage and subjected to delays between harvesting and freezing.

Choose a superior variety

Varieties that excel as fresh products have been found, in general, to be suitable for freezer storage. Ratings for a number of varieties of fruits and vegetables are shown on pages 15 and 16. These ratings are based on tests made in the food research laboratory of the Home Economics Department at the University of Illinois. They are offered only as a partial guide to selection, since many common Illinois varieties not yet tested will doubtless give good products when frozen. A few of the fruits are not grown in Illinois. Their ratings are therefore based on lots that were bought on the local market, as Illinois people would usually buy them.

WASH AND SORT CAREFULLY

 Wash the fruit or vegetable thoroughly in clean cold water. Handle fruit gently, a small amount at a time. Discard all material that is injured, bruised, or otherwise not up to standard. This treatment will remove dirt particles and reduce the number of bacteria. Use special care in sorting because even a small quantity of inferior material can spoil the flavor of several cartons of food.

BLANCH VEGETABLES ACCORDING TO DIRECTIONS

 Vegetables that are to be frozen must first be blanched (scalded) if the greatest possible amounts of color, flavor, texture, and nutritive value are to be retained. Of the vegetables that have been tested, rhubarb is the only one that is satisfactory when it is not blanched before being frozen. Precooking beets and winter squash makes them easier to handle than if they are blanched. Tomatoes are simmered before the juice is extracted.

Weighing the vegetable and using the right amount of boiling water are necessary for a careful job of blanching. Here 2 pounds of spinach are ready to go into 10 quarts of boiling water for one minute. (Figure 1)

To blanch vegetables in boiling water, weigh a small quantity of the vegetable in a wire basket or sieve, and lower into a kettle of boiling water (see Figure 1). Hold there for the required time (see table 1). Count the time from the moment the vegetable is put into the water.

Keep the cover on the kettle during the blanching period, and heat the water continuously. Usually the water will not boil again while the vegetable is being blanched.

After blanching the vegetable, cool it at once in a large kettle of cold running water. When running water is not available, ice water or several kettles of cold water can be used. (Figure 2)

When the vegetable has been in the water the required time, lift the basket or sieve out of the water and plunge it and its contents into a large container of cold water. Have container under cold-water faucet so you can cool the vegetable quickly in running water (see below). Ice water may be used instead of running water. If you do not have running cold water or ice, use several containers, sometimes as many as four. When the water gets slightly warm in one, put the vegetables in the next one.

just as soon as the vegetable has cooled, drain it thoroughly. It is important to remove all excess water. Pack at once.

(If the blanching kettle is large enough, 2 pounds of a vegetable be put in twice the amount of boiling water indicated in Table 1. Blanch for the same length of time.)

Blanching water can be used more than once -as long as it s clean and is not too discolored. Be sure to add enough water time to bring the total amount to the full measure. Remember t the water should always be boiling when the vegetable is put into it.

USE SUGAR OR SUGAR SIRUP WITH FRUITS

 Sirup may preserve the color of light fruits, such as apricots and peaches, that darken with air contact. Juicy fruits are better packed with sugar, as the sugar draws the fruit's juices to form the sirup. Blueberries and cranberries freeze well without sugar; rasberries and strawberries are only fair. Generally, dry packing is better for pies, and sirup packing is better for dessert uses. Use sugar to one quart of fruit for dry packing.

For directions for processing fruits see pages 9 and IO. To make sirups with approximately the correct proportions of sugar, use the following amounts of water with each cup of sugar: 


    Sirup       Sugar  	Water



30 percent	I cup	2 cups

40 percent	1 cup   1 1/4 cups

50 percent	1 cup   3/8 CUP

60 percent	1 cup   1/2 CUP
The sugar may be dissolved in the water by stirring. If, however, you heat the mixture to dissolve it more quickly (boiling is necessary), be sure to cool it before using.

One-half cup of sugar and ½ cup of light corn sirup can be used instead of 1 cup of sugar with the above amounts of water.

Ascorbic acid helps prevent browning. Peaches and apricots brown less readily if ascorbic acid (vitamin C) is added to the sirup in which they are packed for freezing. Commercial preparations containing vitamin C are in some grocery stores under different trade names. Follow the directions of the manufacturer. Tablets or crystals of ascorbic acid can usually obtained from drugstores. Dissolve three 50-milligram tablets in the amount of sugar sirup needed for a pint carton of fruit (about 1 cup of sirup), or add 1/4 teaspoon of crystals to 4 cups of sugar sirup. Tablets may make the sirup cloudy.

PACKAGING AND FREEZING

Choose a satisfactory container

Use sturdy containers of appropriate size and shape that can be sealed tight and that will not leak. The more nearly moisture-proof and vapor-proof a container is, the better the frozen product will be.

Several types of containers are on the market: rectangular cartons to be used with plastic bags, waxed cartons, glass freezer jars, and containers of aluminum, plastic, or tin. Tight seals can be obtained in most plastic bags by twisting and using rubber bands or paper-covered wire closures. A double seal made in this way affords good protection. Some of the especially prepared bags can be sealed with the heat from an electric curling iron, flat iron, or sealing iron. Different types of containers and a bag closure being used for sealing are pictured on the next page.

Package vegetables after cooling

As soon as the vegetables are cooled after blanching, drain them thoroughly, then pack them and seal the containers. Rectangular cartons with plastic bags are very satisfactory for packaging vegetables.

Package fruits quickly

Put fruit in containers and cover immediately with sugar sirup, unless dry sugar is to be used. If you are using dry sugar, mix it thoroughly with the fruit before putting the fruit in the package. As soon as this is done, seat the package.

Be sure to leave space at the top of the package if you are covering the fruit with sirup or if juicy fruit is mixed with sugar. This will allow room for the contents to expand during freezing. Leave ½ inch for a pint container, 1 inch for a quart container.

Label containers

Most locker companies provide materials for stamping and labeling packages at the locker. If packages are to be kept in a home unit, be sure to label each container with the name of the product and the date on which it was prepared for freezing.

Cylindrical cartons, glass jars, and tin cans are easy to fill and not likely to leak. These take up more space than rectangular containers, however, and some cartons are not moisture-vapor proof. (Figure 3)

Rectangular cartons save freezer space. Those made of moisture-vapor proof materials that can be sealed tight are very satisfactory. [Figure 4]

A rectangular carton with a plastic bag makes a good container for vegetables. The bag may be sealed with a paper-covered wire closure or rubber and. Seals must be air-tight. (Figure 5)

Put foods in freezer without delay

When the containers are filled and sealed, put them in the home freezing unit or take them to the locker. If the trip to the locker cannot be made immediately, the containers can be left in the refrigerator for a short time but not longer than 3 or 4 hours. The temperature of the refrigerator should be about 38 to 45 F.

Remember that the shorter the time between harvesting and freezing fruits and vegetables, the better they will be.

Store at 0 F. or lower

The temperature of freezer storage should be O F. or lower to maintain the best quality in fruits and vegetables. When the temperature is higher than O F., undesirable changes in flavor, color, and texture may take place. The longer the period of freezer storage the more noticeable these changes become.

PREPARING FROZEN FOODS FOR SERVING

Keep fruits and vegetables frozen until needed

Unless the packages can be kept frozen at home, only a few should be taken out of the storage locker at one time. Once food has been removed from a freezer, it should be cooked or used as soon as possible. After frozen foods have thawed, the bacteria in them multiply and the food rapidly deteriorates in flavor, texture, and nutritive value.

Thaw fruits just in time for serving

Frozen fruits may be thawed in the refrigerator, or at room temperature, or by putting the container in cold running water. They are more appetizing if served while a few ice crystals are still present. Approximate times for thawing pint containers of sliced peaches packed with a 50 percent sugar sirup are 12 hours in the refrigerator, 3 hours at room temperature, and l ½ hours in cold running water. These times vary with the size of the container, the fruit being thawed, the type of pack, and tile temperature in the refrigerator or room or the temperature of tile water.

Leave containers sealed until the fruit is to be served. This precaution is especially important with frozen peaches, since they darken very quickly when thawed and exposed to the air.

Frozen fruits can be served in several ways. Many of them can be used plain or mixed with other fruits. They are good as sauces or ice cream or shortcake, and they make excellent pies and cobblers. Cranberries can be used in raw cranberry relishes or cooked as a sauce. Frozen apple slices are best when they are stewed or used in pies.

Do not thaw vegetables before cooking

To prepare vegetables for the table, take them from the container and place them immediately in a small amount of boiling salted water (see table 3]. When a vegetable is frozen in a solid mass (for example, spinach), break it into smaller pieces as it thaws in the hot water.

Count the cooking time from the moment till water returns to boiling after the vegetable has been added. Mushrooms and squash are exceptions to the above directions. Mushrooms can be sauteed (fried lightly and quickly) in butter. Squash should be first Heated in the top of a double boiler. It can then be prepared for serving in any way that cooked fresh squash customarily prepared.

Corn, peas, and snap beans are also very good cooked by a "butter boil" method. Add a pint carton of vegetable to 1 tablespoon of butter or margarine, 3 tablespoons of water, and ½ teaspoon of salt in a heavy saucelpan. Cook covered for 7 or 8 minutes, stirring once during- the cooking period.

SUITABILITY OF SOME VARIETIES

 Not all varieties of fruits and vegetables freeze equally well. The following ratings apply to those varieties that have been tested in the Home Economics food research laboratory at the University of Illinois. As these tests are continued, other varieties commonly grown in Illinois will doubtless prove satisfactory. Each rating is an average of a number of tests. Four descriptive ratings are used liere: very good, high good, good, and low good. Varieties of fruits and vegetables which rated high fair, fair, or low fair and varieties of vegetables not grown extensively in Illinois at present are not included.

VEGETABLES

Asparagus

Beet greens

Beets

Broccoli

Cauliflower

Corn

Limabeans

Peas

Rhubarb

Snap beans

Soybeans

Spinach

Squash, summer

Squash, winter

Swiss chard

FRUITS

Apples

Apricots

Blackberries and dewberries

Blueberries

Cherries

Gooseberries

Grapes

Peaches

Plums

Raspberries

Strawberries

For other varieties which are recommended for Illinois gardens, see Illinois Agriculture Extension Service Circular 1150, Vegetable Gardening for Illinois.

Variations in seasons and in degree of maturity, difficulties in securing representative samples, and possibly other factors may explain the differences in the ratings of some closely related strains and varieties.

These varieties were purchased on the market. The quality of the purchased fruit lowered the rating of some of the frozen products.

This circular was prepared by Frances 0. Van Duyne, former Professor of Foods, and revised by Mary Keith, Foods Extension Specialist and Assistant Professor of Foods and Nutrition. Urbana, Illinois, Revised March, 1983

Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbana-Champaign.

The Illinois Cooperative Extension Service provides equal opportunities in programs and employment.

To 8-84-262M-lm
10M-87-67084

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