From Antivist

Drying is the oldest method of preserving food. Throughout history, the sun, the wind, and a smokey fire were used to remove water from fruits, meats, grains, and herbs. It requires a safe place to spread the food where dry air in large quantities can pass over and beside thin pieces.

Dry, clean air including dry cold air from any source will dehydrate food.


General guidelines for fruits and vegetables

  • Good quality food cut in thin pieces, not more than about 1/4 to 3/8 inch thick)
  • Spread thinly on trays initially so there is a third to a half of the screen area clear for the passage of air. Can be more compact after the first moisture is gone.
  • Label all food on the trays and carry the label along through processing to storage.
  • Typical drying times range from 1 to 3 days, again depending on sun, air movement, humidity, and type of food.

Thick vegetables need to be blanched or lightly pre-cooked. Leafy vegetables may be wilted slightly with steam, or dried directly from the garden. Cook potatoes and green beans completely. Fruit is pretreated by dipping in quite sour lemon water, or Ascorbic Acid (Vit.C) 2000mg/quart. After a short soak, the fruit is drained and spread on trays. This retards browning. (Later, the sour soak water flavored by the fruit can be used as a concentrate for making cool drinks.) Sugar, honey or salt are optional. Sulfuring is no longer used in most homes due to the possibility of breathing the hazardous fumes and allergic reactions to sulfur compounds. It has been found to be unnecessary anyway.

To test if food is sufficiently dried, remove a piece and let it cool. Vegetables should be brittle. Fruits because of their sugar content may never get beyond a firm bend or leather quality. If they do become brittle, it is o.k. They just need a little more soaking or chewing time for full flavor to develop.

Air flow

As much food surface as possible should be exposed to warm, dry, moving air. Good air flow is extremely important in removing moisture from food. Some dryers use natural convection only, others use a fan. The addition of a fan will make even air circulation more likely. A fan with two speeds is desirable. High speed is used at the beginning of the drying period when moisture is readily available at the surface. Low speed is then used to slowly remove the remaining moisture.

The two basic kinds of air flow systems are horizontal and vertical. Horizontal flow moves air across the top and bottom of food and is considered the best system. Vertical air flow is more easily blocked by food shelves.

Sun drying

Racks or screens placed on blocks allow for better air movement around the food. Because the ground may be moist, it is best to place the racks or screens on a concrete driveway or if possible over a sheet of aluminum or tin. The reflection of the sun on the metal increases the drying temperature.

Screens need to be safe for contact with food. The best screens are stainless steel, teflon-coated fiberglass and plastic. Avoid screens made from "hardware cloth." This is galvanized metal cloth that is coated with cadmium or zinc. These metals can oxidize, leaving harmful residues on the food. Also avoid copper and aluminum screening. Copper destroys vitamin C and increases oxidation. Aluminum tends to discolor and corrode.

Because birds and insects are attracted to dried fruits, two screens are best for drying food. One screen acts as a shelf and the other as a protective cover. Cheesecloth could also be used to cover the food.

Prepared foods are placed on drying trays. Stainless steel screening and thin wood lath are good materials for home-constructed drying trays. As aluminum screening reacts with acids in the fruit, it is less desirable. Do not use galvanized, copper, fiberglass, or vinyl screening.

Trays measuring about 14" X 24" X1" are an easy size to handle. If trays are to be used in an oven, they should be 1-1/2" smaller in length and width than oven shelves to allow air circulation.

Place trays of food away from dusty roads and yards. Elevate them at least 1" above the table with spools or bricks to allow good air circulation below the food.

Cover the food with a muslin or cheesecloth tent to protect it from insects. Dry fruits in direct sunlight; move trays periodically to assure direct sun exposure. Place vegetables in the shade to prevent excessive color loss.

If weather turns rainy, you will have to complete the drying process using another method.

To destroy insects or their eggs that may be on sun-dried foods and to remove additional moisture in thicker pieces, heat foods in a 150° oven for 30 min.

Oven drying

Either build trays as described for sun drying or convert oven racks to drying racks by stretching muslin or cheesecloth across the oven rack. Secure with toothpicks or long sewn stitches. alternate trays in the oven periodically to assure even drying.

Set oven control at its lowest setting, but not below 140-50°. If using an electric oven, wedge a potholder between oven and door to allow a 1" opening. Moisture from the drying food will vent through this opening. Close the door on a gas oven, as vent will permit moisture to escape.

vine drying

Another method of drying out-of-doors is vine drying. To dry beans (navy, kidney butter, great northern, lima, lentils and soybeans) leave bean pods on the vine in the garden until the beans inside rattle. When the vines and pods are dry and shriveled, pick the beans and shell them. No pretreatment is necessary If beans are still moist, the drying process is not complete and the beans will mold if not more thoroughly dried. If needed, drying can be completed in the sun, oven or a dehydrator.

bamboo basket method

The bigger unit consists of a tray-shaped structure made of bamboo of dimensions 1 m x 16 cm x 15 cm height with slant sides for wider incidence of sun light. It is covered with black polyethylene sheet inside, which acts as absorbing material. In areas where there is difficulty in procuring black high density polyethylene sheet the inside portion of the basket is coated with enamel black paint and covered with transparent HDP cover. Over the basket, a transparent polyethylene sheet is provided with opening at two sides and the other two sides being fixed to enable for easy lifting to put the contents. The top poluethylene sheet is provided with Velcro for fixing. The basket is provided with holes on the sides for easy passage of air which avoids formation of water vapour at the top. This design costs just Rs 150 in South India.

The second system is meant for drying small quantities in rural areas. In this a winnowing basket is provided with similar arrangement as in the previous case. This costs Rs 50.

Experiments reveal that on an average it saves half of the time to dry the contents when compared to open drying.

The advantages offered are: (a) The contents dry quickly; (b) The contents will be hygienic as they are protected from dust because of cover; (c) The contents are free from bird menace like crows as there is a thick covering; (d) When sudden rain comes, the contents are protected because of the polythylene covering; (e) The units are light and easy to carry; (f) All the materials used in the fabrication of these simple solar driers are available locally and can be fabricated by local people; (g) Fabrication of this simple gadget helps generate rural employment.

drying corn

After lightly baking corn, (enough to make the kernels pucker), pull the husks back and hang them. Care must be used that the ears are separated and do not touch, or they can mold.

Drying Times

Drying time varies widely because of the method selected and the size and amount of moisture in food pieces. Sun drying requires the most time; an electric dehydrator requires the least. Vegetables take from 4 to 12 hours to dry; fruits take 6-20 hours. Meats require about 12 hours. Making raisins from grapes may require days/weeks when dried outside.

When testing foods for dryness, remove a piece from the center of the drying tray and allow it to come to room temperature. Fruits and meat jerky should be leathery and pliable; vegetables should be brittle. Conditioning Dried Foods

Food should be conditioned for a week before being packaged for long-term storage. To condition food, place it in a container such as a cloth sack or a clear, covered container and allowing any remaining moisture to redistribute itself through the fruit.

If using a clear, covered container, watch for moisture beads. If they form, continue drying food. If using the cloth bag, hang it in a convenient location and shake the bag daily to redistribute food and moisture.

Storing Dried Foods

Package dried foods in glass jars, food-grade plastic storage containers, or plastic food-storage bags. Make sure the package has an airtight seal. It is a good idea to package dried foods in small amounts, because after the package is opened, the food can absorb moisture from the air and quality deteriorates.

Store containers of dried foods in a cool, dark, dry area such as a basement or cellar. Exposure to humidity, light or air decreases the shelf life of foods. Dried foods store well at room temperature for a month. Refrigerate foods if they will be used within three months; freeze foods for storage periods between three months and one year. Foods should be used within one year.

Using Dried Foods

Rehydrate vegetables by soaking them in 1-1/2-2 cups of water for each cup of dried vegetable. If necessary, add more water during the soaking process. Heat and eat.

Cover dried fruit with boiling water and let stand for 5 min. Drain. Dried fruit may also be steamed for 3-5 min. until plump. Fruits may be eaten immediately or used in a recipe.

Making Fruit Leather

Fruit leathers, also called fruit roll ups, can be made from almost all fruits or combinations of fruits. However, peaches, apricots, cherries, and nectarines are ideal. Pears and apples, sufficiently softened, also work well.

Wash well, peel (if desired), cut into pieces, and puree fruit in a blender. Sweeten to taste with sugar or honey. Spread evenly, no more than 1/4" deep, on a cookie sheet. The cookie sheet should either be lightly sprayed with a vegetable shortening or covered with plastic paper.

If using plastic paper, tape edges down to prevent them from folding into the puree. Dry fruit leather until it is slightly tacky to the touch.

When dried, lift leather (including plastic paper if used), and roll or cut into small sections and roll. Storage recommendations are the same as those described previously.

Nutritional Value of Dried Foods

Dried foods retain their protein, mineral and vitamin A content fairly well if soaking water is also consumed. Because they are concentrated into a small mass, dried foods can also be high in calories. It's important to brush teeth after eating dried fruit because they stick to the teeth.

other methods

Draping food over branches or spreading it on wide shallow baskets on the roof is an old widespread tradition still in use around the world. Many other arrangements have been used to support a thin spread of food pieces. Some options that have been used are to thread the pieces on a cord or a stick and hang it over a fire, wood stove or from the rafters. Or one can bundle herbs or strawflowers and suspend them from bushes or a door knob or nails in rooms with good ventilation. Screen doors placed across chairs or sheets hung between clothes lines or possibly on a quilting frame have also been used. Vans, clean garages, or backseats of cars can be safe places to spread trays of drying food just as well as specially constructed cabinets. In the pioneer tradition food might be spread in the attic or in an upstairs room with screened windows wide open.


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