Reviewed June 1994

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Quality for Keeps: How to Dry Foods at Home

Karla Vollmar Hughes and Barbara J. Willenberg
Department of Food Science and Human Nutrition

Drying does not improve the quality of fruits or vegetables. Therefore it is important to choose produce of high quality and at the desired stage of ripeness. Before drying, produce should be sorted and that of inferior quality used in some other manner besides preserving. Follow directions for preparing and treating carefully, so that quality is maintained.

Fruits

Fruits should be ripe or just ready to eat for best quality when dried. Fruits with high water content, such as citrus fruits, are not suitable for drying. Do not use under-ripe produce. Fruits to be used in leathers can be overripe as long as they are not spoiled.

Prepare only as much food as you can dry at one time. Refer to the chart for notes on specific types of fruits. Wash fruit in cold running water to remove dirt, insect larvae and any surface microorganisms. Trim away bruises or soft spots. Remove stems, cores and pits. In some cases, skins should be removed because they will become tough or brittle when dried. (See chart.) Slice fruits uniformly, about 1/4 to 1/2 inch thick, for even drying, shorter drying time, and more nutritious, better quality food.

Holding solutions

Prepare a holding solution when slicing large amounts of fruits that tend to brown. This step is not necessary if only a small amount of fruit is being prepared.

Use 1 tablespoon of pure, crystalline ascorbic acid or 1/4 teaspoon sodium bisulfite per quart of water. Or use a commercial antioxidant such as Fruit Fresh®; follow label directions for cut fruit. Hold fruit in solution no longer than one hour, because the fruit will absorb moisture and it will take longer for drying to be complete.

Pretreatments

Fruits such as apples, pears, peaches, nectarines and apricots require sulfur treatments to prevent browning during the drying process. Sulfur treatments protect vitamins A and C during drying and storage, help retain fresh fruit flavor and increase the shelf life of the fruit. Sulfur treatments destroy thiamin, but most fruits are not good sources of thiamin, so this is not a great concern.

Two types of sulfur treatments are used -- sulfuring and sulfite dips (sulfiting).

Soaking times vary with the type of fruit and thickness of slices. (See chart for specific fruits.) Fruit slices 1/4 to 1/2 inch thick require at least five minutes. Use 1/2 teaspoon sodium bisulfite or equivalent per quart of water. These chemicals must be of food-grade quality and usually are available at winemaking supply stores, natural foods stores or pharmacies. Prices vary considerably.

Caution
 Recent research indicates that certain asthmatics may react adversely to sulfites. Persons who are sensitive to sulfites should avoid preparing or eating sulfite-treated foods. Sulfite fumes will be given off during the drying process; also, if sodium bisulfite is added to water for steam-blanchings, fumes will escape with the steam.

Checking

Cherries, grapes and small, dark plums that are dried whole may require a short heat treatment, called checking, to remove a naturally occurring waxy coating and to crack the skins. Checking speeds up drying by allowing interior moisture to evaporate. If checking is not done, there is a greater chance of case hardening, which is the formation of a hard shell on the outside with moisture trapped within the fruit. This may occur more readily when fruit is dried in an oven rather than a dehydrator.

Fruit to be checked should be immersed in briskly boiling water for 30 to 60 seconds, then dunked in cold water and drained on paper towels. Treatment time depends on the thickness of skins. Checking can be done in a microwave oven by heating on high about 20 to 30 seconds, then chilling. Some flavor loss may result from the checking process.

Fruit leathers

A variety of fruits can be used for leathers. Some favorites include apples, apricots, bananas, peaches, pears, plums. They can be used singly or in combinations. Spices such as cinnamon, cloves, ginger, nutmeg and mint add extra flavor. Fruits are naturally sweet, so usually it is not necessary to add sweetener.

Making fruit leather is a snap

Use a blender or food processor to puree about 1 cup of fruit chunks at a time. To keep light-colored fruits from turning dark, add 1 tablespoon lemon or lime juice per quart of fruit puree; or cook fruit until soft and then puree.

Thicken juicy puree to shorten the drying time. Place pureed fruit in a deep, heavy saucepan and cook over low heat, stirring constantly, until mixture thickens. Remove from heat and cool. If tart, add 1 tablespoon honey or white corn syrup per quart of puree. Do not use granulated sugar, because it may crystallize during storage, resulting in a brittle leather. Drying concentrates flavors, making the fruit leather taste sweeter than the puree. For extra flavor, add 1/4 teaspoon cinnamon or a dash of nutmeg per quart of puree.

Line dehydrator trays or cookie sheets (for oven drying) with plastic wrap. Tape plastic to tray on all four sides to keep it from blowing onto the leather. Pour pureed fruit onto plastic wrap and spread the puree by tilting the tray or cookie sheet. Leave a 1-inch border to allow for spreading during drying.

Fruit puree may take six to 24 hours to dry. Leather is done when it has a leathery appearance and is pliable enough to roll up jelly-roll fashion. Test by separating leather from plastic wrap; if it separates easily it is done. Remove from tray and cool briefly. Place leather on clean plastic wrap and roll up, so plastic separates layers of leather.

Vegetables

Note
Before using sulfites, read Warning information in pretreatments section

Most vegetables need to be blanched before drying to stop enzyme activity. If enzymes are not destroyed, they will produce "off" flavors and the vegetables will turn brown during the drying process as well as during storage. Blanching kills some spoilage organisms, shortens the drying time of some foods and protects vitamins C and A during storage. But it also causes the loss of some water-soluble nutrients. Add 1 teaspoon sodium bisulfite per cup of water for steam-blanching corn, green beans and potatoes to improve keeping quality of those vegetables. Do not add sodium bisulfite when blanching in boiling water because it will give vegetables a sulfur taste.

Blanching times vary with vegetables and thickness of slices. (See chart.) For boiling-water blanching, immerse no more than 1 pound of vegetables per gallon of boiling water. Begin timing when vegetables are put into water.

Meat jerky

Use lean cuts of meat such as flank or round steak. The leaner the meat, the better the product. Cut partially frozen meat into slices 1/4 inch thick. Slices should be 1 to 1-1/4 inches wide and several inches long. Uniform slices will shorten drying time. Four pounds of raw meat will yield about 1 pound of jerky.


Caution
 Milk, milk products and eggs are not recommended for home drying because of the high risk of food poisoning. Commercially dried milk and egg products are processed rapidly at temperatures high enough to prevent bacterial contamination. Home dryers cannot duplicate this process, and the safety of home-dried milk and egg products cannot be guaranteed.

Table 1
A guide to home drying of fruits
For portable dehydrators, set temperature at 140 degrees Fahrenheit for best results.

Note
A dehydrator is suggested rather than an oven because of time needed to dry fruits, especially those in large pieces. Range ovens can be used, but time and fuel expenditure will be great for the amount dried. Apples are the only fruit practical to dry in large pieces in the home oven.

Apples

1Equivalent sulfite solutions
1/2 teaspoon sodium bisulfite to 1 quart water
1 teaspoon sodium sulfite to 1 quart water
2 teaspoons sodium metabisulfite to 1 quart water

Apricots

1Equivalent sulfite solutions
1/2 teaspoon sodium bisulfite to 1 quart water
1 teaspoon sodium sulfite to 1 quart water
2 teaspoons sodium metabisulfite to 1 quart water

Bananas

Berries: Firm, suitable for snacks or cooking

Berries: Soft (Not a superior product)

Cherries, sweet

Citrus peel

Grapes: Muscat, Tokay or any seedless grape

Nectarines and peaches

1Equivalent sulfite solutions
1/2 teaspoon sodium bisulfite to 1 quart water
1 teaspoon sodium sulfite to 1 quart water
2 teaspoons sodium metabisulfite to 1 quart water

Pears

1Equivalent sulfite solutions
1/2 teaspoon sodium bisulfite to 1 quart water
1 teaspoon sodium sulfite to 1 quart water
2 teaspoons sodium metabisulfite to 1 quart water

Pineapple

Plums (prunes)

Table 2
A guide to home drying of vegetables
For oven and portable dehydrators, set temperature at 140 degrees Fahrenheit.

Beans, green

Beets

Broccoli

Brussels sprouts

Cabbage

Carrots

Cauliflower

Celery

Corn on the cob

Corn, cut

Eggplant

Horseradish

Mushrooms

Caution
 The toxins of poisonous varietiedifferentiates of mushroom are not destroyed by drying or by cooking. Only an expert can between poisonous and edible varieties.

Okra

Onions

Parsley

Peas

Peppers and pimentos

Potatoes

Spinach, kale, chard, mustard and other greens

Squash, banana

Squash, Hubbard

Squash, summer

Tomatoes, for stewing

GH1563, reviewed June 1994