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).
- Sulfuring is the most effective sulfur treatment and results in a minimal loss of water-soluble nutrients; however, it is not very practical. The fumes will irritate eyes and breathing passages, so it must be done outside. It is used primarily for fruits that are going to be sun dried, because sulfured fruits should not be dried inside. Sulfuring is more expensive, more time consuming and more complicated than using sulfite dips. Because sun drying is not a recommended procedure for Missouri, sulfuring is not recommended as an alternative for pretreating fruits.
- Sulfite dips can be prepared and used in the kitchen and sulfite-dipped fruits can be dried indoors. There are several disadvantages of sulfite dips. Penetration of sulfite may be uneven, resulting in uneven color retention. The loss of water-soluble nutrients is greater than in sulfured fruit. And, finally, the fruit may absorb water, which will result in a longer drying time.
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
- Preparation
Peel and core, cut into slices or rings about 1/8 inch thick
- Pretreatment
- Sulfur -- sulfite*
5 minutes
- Steam blanch
3 to 5 minutes, depending on texture
- Dehydrator drying time
6 to 12 hours
- Test for dryness, cool before testing
Soft, pliable, no moist area in center when cut
*Equivalent 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
- Preparation
Pit and halve for steam blanching or sulfuring. Leave whole for water blanching. Pit and halve after blanching
- Pretreatment
- Sulfur -- sulfite*
5 minutes
- Steam blanch
3 to 4 minutes
- Water blanch
4 to 5 minutes
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Soft, pliable, no moist area in center when cut
*Equivalent 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
- Preparation
Use solid yellow or slightly brown-flecked bananas. Avoid bruised or overripe bananas. Peel and slice 1/4 to 3/8 inch thick, crosswise or lengthwise.
- Pretreatment
Dip into mixture of lemon juice (1 tablespoon), honey (1/4 cup) and water (1/4 cup) or ascorbic acid or pineapple juice. Pretreat if a lighter color is desired.
- Dehydrator drying time
8 to 10 hours
- Test for dryness, cool before testing
Pliable to crisp
Berries: Firm, suitable for snacks or cooking
- Preparation
Wash and drain berries with waxy coating (blueberries, cranberries, currants, gooseberries, huckleberries)
- Pretreatment
Plunge into boiling water 15 to 30 seconds. Stop cooking action by placing fruit in ice water. Drain on paper towels.
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Leathery and pliable with no moisture
Berries: Soft (Not a superior product)
- Preparation
(Blackberries, dewberries, boysenberries, loganberries, raspberries, strawberries, youngberries.) Sort and wash carefully. If seeds are too numerous, make into puree, sieve out seeds, and use for fruit leathers. Or dry, make into powder in blender or food processor, and use for fruit-flavored beverages.
- Pretreatment
Puree. A short heat treatment, 30 seconds steam, facilitates the removal of seeds and ensures a better color.
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Dry and leathery or crisp
Cherries, sweet
- Preparation
Royal Ann or black variety is best. Stem, wash, drain, and pit fully ripe cherries. Cut in half, chop, or leave whole.
- Pretreatment
Check whole: Dip in boiling water 30 seconds to crack skin, if desired. Cut and pitted: No pretreatment necessary.
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Shriveled, leathery, dry, no pockets of moisture
Citrus peel
- Preparation
Peels of citron, grapefruit, kumquat, lime, lemon, tangelo, and tangerine can be dried. Thick-skinned navel orange peel dries better than thin-skinned Valencia peel. Wash thoroughly.
- Pretreatment
No pretreatment, Remove outer 1/8 inch of peel. Avoid white bitter pith.
- Dehydrator drying time
8 to 12 hours
- Test for dryness, cool before testing
Crisp
Grapes: Muscat, Tokay or any seedless grape
- Preparation
Leave whole
- Pretreatment
No treatment necessary
- Dehydrator drying time
12 to 20 hours
- Test for dryness, cool before testing
Raisinlike texture, no moist center
Nectarines and peaches
- Preparation
When sulfiting, pit and halve; if desired, remove skins. For steam and water blanching, leave whole, then pit and halve.
- Pretreatment
- Sulfite**
5 to 15 minutes
- Steam blanch
8 minutes
- Water blanch
8 minutes
- Dehydrator drying time
36 to 48 hours
- Test for dryness, cool before testing
Soft, pliable, no moist area in center when cut
**Equivalent 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
- Preparation
Cut in half and core, remove peel preferred
- Pretreatment
- Sulfite**
5 minutes
- Steam blanch
6 minutes, will be soft if peeled
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Soft, pliable, no moist area in center when cut
**Equivalent 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
- Preparation
Use fully ripe, fresh pineapple. Wash, peel and remove thorny eyes. Slice lengthwise and remove core. Cut in 1/2 inch slices, crosswise.
- Pretreatment
No treatment necessary
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Leathery but not sticky
Plums (prunes)
- Preparation
For oven-drying or dehydrator, rinse in hot tap water. Leave whole.
- Pretreatment
No treatment necessary. Check if dried whole.
- Dehydrator drying time
24 to 36 hours
- Test for dryness, cool before testing
Leathery; pit should not slip when squeezed if prune is not cut
Table 2
A guide to home drying of vegetables
For oven and portable dehydrators, set temperature at 140 degrees Fahrenheit.
Beans, green
- Preparation
Wash thoroughly. Cut in short pieces or lengthwise.
- Blanching time
- Steam blanch
2 to 2-1/2 minutes
- Water blanch
2 minutes
- Drying time
- Dehydrator
8 to 14 hours
- Oven
3 to 6 hours
- Characteristics
Leathery, brittle
Beets
- Preparation
Cook as usual. Cool; peel. Cut into shoestring strips 1/8 inch thick.
- Blanching time
Already cooked; no further blanching required
- Drying time
- Dehydrator
10 to 12 hours
- Oven
3 to 5 hours
- Characteristics
Brittle
Broccoli
- Preparation
Trim, cut as for serving. Wash thoroughly. Quarter stalks lengthwise.
- Blanching time
- Steam blanch
3 to 3-1/2 minutes
- Water blanch (preferred method)
2 minutes
- Drying time
- Dehydrator
12 to 15 hours
- Oven
3 to 4-1/2 hours
- Characteristics
Crisp
Brussels sprouts
- Preparation
Cut in half lengthwise through stem.
- Blanching time
- Steam blanch
6 to 7 minutes
- Water blanch
4-1/2 to 5-1/2 minutes
- Drying time
- Dehydrator
12 to 18 hours
- Oven
4 to 5 hours
- Characteristics
Tough to brittle
Cabbage
- Preparation
Remove outer leaves; quarter and core. Cut into strips 1/8 inch thick.
- Blanching time
- Steam blanch (steam until wilted)
2-1/2 to 3 minutes
- Water blanch
1-1/2 to 2 minutes
- Drying time
- Dehydrator
10 to 12 hours
- Oven
1 to 3 hours
- Characteristics
Brittle
Carrots
- Preparation
Use only crisp, tender carrots. Wash thoroughly. Cut off roots and tops; peel, cut in slices or strips 1/8 inch thick.
- Blanching time
- Steam blanch
3 to 3-1/2 minutes
- Water blanch
3-1/2 minutes
- Drying time
- Dehydrator
10 to 12 hours
- Oven
3-1/2 to 5 hours
- Characteristics
Tough to brittle
Cauliflower
- Preparation
Prepare as for serving.
- Blanching time
- Steam blanch
4 to 5 minutes
- Water blanch (preferred method)
3 to 4 minutes
- Drying time
- Dehydrator
12 to 15 hours
- Oven
4 to 6 hours
- Characteristics
Crisp
Celery
- Preparation
Trim stalks. Wash stalks and leaves thoroughly. Slice stalks.
- Blanching time
- Steam blanch
2 minutes
- Water blanch
2 minutes
- Drying time
- Dehydrator
10 to 16 hours
- Oven
3 to 4 hours
- Characteristics
Very brittle
Corn on the cob
- Preparation
Husk, trim
- Blanching time
- Steam blanch (steam until milk does not exude from kernel when cut)
2 to 2-1/2 minutes
- Water blanch
1-1/2 minutes
- Drying time
- Dehydrator
12 to 15 hours
- Oven
4 to 6 hours
- Characteristics
Brittle
Corn, cut
- Preparation
Prepare in the same manner as corn on the cob, except cut the kernels from the cob after blanching.
- Blanching time
- Steam blanch (steam until milk does not exude from kernel when cut)
2 to 2-1/2 minutes
Water blanch
1-1/2 minutes
- Drying time
- Dehydrator
6 to 10 hours
- Oven
2 to 3 hours
- Characteristics
Dry, brittle
Eggplant
- Preparation
Wash, trim, cut into 1/4-inch slices.
- Blanching time
- Steam blanch
3-1/2 minutes
- Water blanch
3 minutes
- Drying time
- Dehydrator
12 to 14 hours
- Oven
3-1/2 to 5 hours
- Characteristics
Leathery
Horseradish
- Preparation
Wash; remove small rootlets and stubs. Peel or scrape roots. Grate.
- Blanching time
None
- Drying time
- Dehydrator
4 to 10 hours
- Oven
3 to 4 hours
- Characteristics
Brittle
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.
- Preparation
Scrub thoroughly. Discard any tough, woody stalks. Cut tender stalks into short sections. Do not peel small mushrooms or "buttons." Peel large mushrooms, slice.
- Blanching time (minutes):
None
- Drying time
- Dehydrator
8 to 10 hours
- Oven
3 to 5 hours
- Characteristics
Leathery
Okra
- Preparation
Wash, trim, slice crosswise in 1/8 to 1/4 inch disks.
- Blanching time (minutes):
None
- Drying time
- Dehydrator
8 to 10 hours
- Oven
4 to 6 hours
- Characteristics
Very brittle
Onions
- Preparation
Wash, remove outer "paper shells." Remove tops and root ends, slice 1/8 to 1/4 inch thick.
- Blanching time
None
- Drying time
- Dehydrator
3 to 9 hours
- Oven
3 to 6 hours
- Characteristics
Brittle
Parsley
- Preparation
Wash thoroughly. Separate clusters. Discard long or tough stems.
- Blanching time (minutes):
None
- Drying time
- Dehydrator
1 to 2 hours
- Oven
2 to 4 hours
- Characteristics
Brittle, hard
Peas
- Preparation
Shell
- Blanching time
- Steam blanch
3 minutes
- Water blanch
2 minutes
- Drying time
- Dehydrator
8 to 10 hours
- Oven
3 hours
- Characteristics
Wrinkled, green
Peppers and pimentos
- Preparation
Wash, stem, core. Remove "partitions." Cut into strips, slice or dice.
- Blanching time (minutes):
None
- Drying time
- Dehydrator
8 to 12 hours
- Oven
2-1/2 to 5 hours
- Characteristics
Leathery to brittle
Potatoes
- Preparation
Wash, peel. Cut into shoestring strips 1/4 inch thick, or cut in slices 1/8 inch thick.
- Blanching time
- Steam blanch
6 to 8 minutes
- Water blanch
5 to 6 minutes
- Drying time
- Dehydrator
8 to 12 hours
- Oven
4 to 6 hours
- Characteristics
Brittle
Spinach, kale, chard, mustard and other greens
- Preparation
Trim, wash thoroughly
- Blanching time
- Steam blanch (steam until thoroughly wilted)
2 to 2-1/2 minutes
- Water blanch
1-1/2 minutes
- Drying time
- Dehydrator
8 to 10 hours
- Oven
2-1/2 to 3-1/2 hours
- Characteristics
Crisp
Squash, banana
- Preparation
Wash, peel, slice in strips about 1/4 inch thick.
- Blanching time
- Steam blanch
2-1/2 to 3 minutes
- Water blanch
1 minute
- Drying time
- Dehydrator
10 to 16 hours
- Oven
4 to 5 hours
- Characteristics
Tough to brittle
Squash, Hubbard
- Preparation
Cut or break into pieces. Remove seeds and cavity pulp. Cut into 1-inch-wide strips. Peel rind. Cut strips crosswise into pieces about 1/8 inch thick.
- Blanching time
- Steam blanch
2-1/2 to 3 minutes
- Water blanch
1 minute
- Drying time
- Dehydrator
10 to 16 hours
- Oven
4 to 5 hours
- Characteristics
Tough to brittle
Squash, summer
- Preparation
Wash, trim, cut into 1/4-inch slices
- Blanching time
- Steam blanch
2-1/2 to 3 minutes
Water blanch
1-1/2 minutes
- Drying time
- Dehydrator
10 to 12 hours
- Oven
4 to 6 hours
- Characteristics
Leathery to brittle
Tomatoes, for stewing
- Preparation
Steam or dip in boiling water to loosen skins. Chill in cold water. Peel. Cut into sections about 3/4 inch wide, or slice. Cut small pear or plum tomatoes in half.
- Blanching time
- Steam blanch
3 minutes
- Water blanch
1 minute
- Drying time
- Dehydrator
10 to 18 hours
- Oven
6 to 8 hours
- Characteristics
Leathery
GH1563, reviewed June 1994