“Dehydrating Food: Wrinkles Have Never Looked Better,” Ensign, June 1974, 40
When the water content of foods is reduced to about 10 percent, microorganisms that cause spoilage go into “hibernation”; because of this, foods may be preserved almost indefinitely. Dehydrating foods changes the color and flavor—not into something worse, but into something different. And most of the vitamins and minerals are still there.
Following are the results of our family’s ongoing research about dehydrating foods.
1. Selecting foods for dehydration. Most fruits and vegetables and some meats will dehydrate successfully. Citrus products won’t. The raw product should be of good quality and fully mature, but should still be firm. Remove any blemish. Peeling is optional except in obvious cases like bananas.
2. Slicing. An ideal thickness is approximately 3/16 inch. Drying a chunk as large as a peach half takes so long that the fruit often spoils first. Using a thin stainless steel blade to slice reduces bruising and discoloration.
3. Treatment. This is the only step where fruits and vegetables must be treated differently.
Most vegetables must be steam-blanched to destroy the maturation enzyme. Place the sliced vegetables in a steamer, a colander, or a deep-frying basket and suspend over boiling water. The time required depends on the vegetable and varies from two minutes for celery to 40 minutes for red beets, which must be fully cooked before slicing and dehydrating.
The treatment for fruit depends upon the variety of the fruit and the method of dehydration. For example, in sundrying, fruit must be protected from oxidation with a sulphur fume treatment or by being soaked in a sodium bisulfite and water solution for 30 minutes, then drained thoroughly. (Complete directions for each fruit need to be obtained from professional dehydrators, county agents, or state extension services.)
Any dehydration method taking less than 48 hours will not need the above treatment. However, fruits that darken when exposed to the air (apples, bananas, and so forth) should be sliced and dipped immediately in a solution of water and ascorbic acid (like Fruit Fresh, which is available in grocery stores), water and erythorbic acid, or similar material, available through some druggists or wholesalers. Soak for two minutes, remove, and drain thoroughly.
The meats we have dehydrated include beef and chicken. We have also made jerky. If you wish to reconstitute beef or chicken after you dehydrate it, then cook it completely first. Then chill the meat for easier handling. After it is chilled, slice it 1/4 inch thick and remove all fat.
Herbs should be mature (but not old), thoroughly washed, and not blanched.
4. Place on shelves or trays. Air circulation is the key for successful dehydrating. Use shelves, trays, cloth netting, or screens, and arrange food only one layer deep until you know what works well. Several vegetables or fruits can be dehydrated at the same time on separate trays, but do not mix fruits and vegetables in the same dryer load, as fruits will pick up vegetable tastes. (Heavy nylon net between the shelves and some sticky fruit, like bananas, will keep the pieces from sticking to the shelves.)
5. Dehydration. If you want a high quality product, the moisture must be removed as rapidly and continuously as possible without damaging or cooking the food. Dr. D. K. Salunkhe, professor of plant science at Utah State University, identifies 145 degrees F. as the point where vitamin loss accelerates. If the temperature is below 145 degrees, essentially all nutrients will be retained except for the extremely unstable vitamin C.
Some dehydration methods are:
Sun dehydration. Products are spread on trays tilted to receive direct sunlight. The product must be protected from insects, blowing dust, rain, and evening dew. There is more danger of spoilage with this slow method, especially if cloudy days intervene. Before storing, sun-dehydrated products should be placed in a dehydrator or oven for 20–30 minutes to complete the drying process.
Oven dehydration. The kitchen should be well ventilated, the oven preheated, and the temperature carefully watched. It must not exceed 145 degrees F. Leave the door of an electric oven open two inches (eight inches for a gas oven) for temperature control and moisture escape. Oven drying has its problems, too: you have to stir to compensate for the lack of air movement, space is limited, and most ovens do not control well at such a low temperature.
Homemade dehydrator: Make your own from a wooden or metal box or old refrigerator by adding a fan, a heating element, a thermostat, shelf supports, and ventilation vents. Experiment to get the proper air movement and temperature.
Commercial dehydrators: Look for one with a heating element, a thermostat, a fan for air circulation, and a means to pull in dry air and expel moist air.
6. Testing for dryness. The time required varies from four to 36 hours in a commercial unit to one to three weeks for sundrying, depending on the item and weather conditions. Remove a sample and cool. Vegetables should be hard and brittle. Fruit should be pliable and leathery; if the fruit cracks, the drying time was too long. Jerky should be stringy and leathery; precooked meat should be crisp. The longer you wish to store it, the drier it should be.
7. Storage. Storage space is where you really save with dehydrated food. Ten pounds of fresh carrots reduces to one pound when dehydrated. One-half bushel of apples will fit in a gallon jar, and 25 pounds of fresh celery reduces to an astounding one pound. However, when all foods are reconstituted, they regain their full original size.
Keep three rules in mind for proper storage: (1) dehydrated food should be kept in airtight containers: glass jars (nicked rims don’t matter since you don’t need a perfect seal), metal cans (especially if lined with food-grade plastic bags and sealed with tight lids), or plastic cooking pouches (sealed with a commercial heat-sealer); (2) temperature should be 60 degrees or below if possible, because food discolors at a rate that doubles for each 12–15 degree rise in temperature; and (3) the food should be stored in darkness. Wrap transparent containers with colored paper, newsprint, or black plastic if the storage room is not completely dark or if windows cannot be covered.
Dehydrated food will last two to three times longer with a small desiccant package (containing a chemical that absorbs moisture) in the container. These packages are available from wholesalers. Examine the food occasionally and redehydrate if there is any indication of moisture.
8. Using dehydrated foods. Dehydrated food is popular as a snack or reconstituted.
Most vegetables can be reconstituted and cooked in approximately one hour, using two cups of water for each cup of food. Carrots will reconstitute in cold water in five or six hours without cooking. Dehydrated swiss chard and other greens can be placed in boiling water for five to ten minutes and then seasoned. Do not salt any vegetables until after they have been reconstituted. You can also make your own vegetable soup mix out of dried vegetables by reconstituting them all together.
Place dehydrated fruit in boiling water, or soak it in either hot or cold water without cooking, until it is reconstituted. Use in recipes calling for fresh fruit, or cook the fruit alone, but do not add sugar before reconstituting.
Dehydrated meat can be added to soups and stews without any reconstitution. Dehydrated herbs and celery leaves can be added to any cooked food for seasoning. Peel, slice, and dehydrate cucumbers until they are brittle, then blend them to a powder and use it to season salad dressing. Almost any vegetable can be powdered after dehydrating for seasoning, purees, soups, baby food, etc.
If directions on preparation and storage are followed, dehydrated foods can last indefinitely. Some people report no deterioration in vegetables they’ve had up to 15 years. Since our family uses, as well as stores, dehydrated foods, there’s no “rotation” problem. And it lasts the first dehydrated cooked meat we made was stored two years ago and it’s still good!