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University of Illinois Extension

Drying

Drying removes the moisture from the food so that bacteria, yeasts and molds cannot grow and spoil food. It also slows down the action of enzymes, but it does not inactivate them. For efficient and safe drying, use a food dehydrator. Select foods suitable for drying. Consider drying fruits, vegetables, seeds, herbs and fruit and vegetable leathers. Dehydrated melon, tomato, meat or fish, including jerky, is not allowed in a cottage food operation.

Outdoor Drying

The high sugar and acid content of fruits allows them to be safely dried outdoors. Vegetables (with the exception of vine-dried beans) are too low in sugar and acid to be safely dried outdoors. A minimum temperature of 85°F with a low humidity level below 60 percent is ideal, but it is not always achievable in Illinois. Plus, because food is exposed to the outdoors, sun dried fruits and vine dried beans need to be pasteurized to kill insects and their eggs. Either freeze dehydrated food at 0°F or below for at least 48 hours or place in a single tray in the oven at 160°F for 30 minutes prior to packaging.

Oven Drying

Foods can be dried in an oven, but it is not very efficient. The oven must be able to be set as low as 140°F. If set higher, the food will be cooked rather than dried. Use a convection oven, which has a fan to circulate air, or leave the conventional oven door open 2-6 inches. Place a fan outside the oven near the door. CAUTION: This is not a safe practice for homes with small children.

Food Dehydrator

A food dehydrator is a small electrical appliance with a heat element and fan. Dehydrators are designed to dry foods quickly at 140°F. Models vary by horizontal air flow or vertical air flow. Horizontal flow reduces flavor mixture if drying different foods at a time.

Food Dehydrator

Photo credit: Jenna Smith

Basic Steps to Drying

  1. Wash and drain all herbs, fruits and vegetables before peeling, chopping, removing cores, pits, seeds, skins, etc. Wash small amounts at a time through several changes of cold water. Do not let the produce soak.
  2. Slice most fruits and vegetables no more than 1/4 –inch thick. Keep pieces uniform in size so they will dry at the same rate. Some fruits, such as berries, dates, cherries or grapes may be left whole.
  3. If drying fruits, pretreat light colored fruits to prevent darkening.
    • Fruit juice dip- use orange, lemon, pineapple, grape or cranberry juice. Place enough juice to cover fruit in a bowl. Soak cut fruit 3-5 minutes. Remove fruit, drain well and place on dehydrator trays sprayed with non-stick cooking spray.
    • Ascorbic acid or commercial ascorbic acid mixture- mix 1 teaspoon (3000 mg) of powdered ascorbic acid in 2 cups water, or mix 1 ½ tablespoons commercial ascorbic acid mixture with 1 quart water. Soak cut fruit 3-5 minutes. Remove fruit, drain well and place on dehydrator trays sprayed with non-stick cooking spray.
    • Honey dip- mix ½ cup sugar with 1 ½ cups boiling water. Cool to lukewarm and add ½ cup honey. Soak cut fruit 3-5 minutes. Remove fruit, drain well and place on dehydrator trays sprayed with non-stick cooking spray.
    • Syrup blanching- combine 1 cup sugar, 1 cup light corn syrup and 2 cups water in a pot. Bring to a boil. Add 1 pound prepared fruit and simmer 10 minutes. Remove from heat. Let fruit stand in hot syrup for 30 minutes. Lift fruit out of syrup, rinse lightly in cold water, drain on paper towels and place on dehydrator trays sprayed with non-stick cooking spray.
  4. If drying vegetables, use blanching times according to Colorado State University Extension guidelines.
    • Water blanching is recommended. Fill a large pot two-thirds full of water, cover and bring to a vigorous boil.
    • Put no more than one quart of the vegetable pieces in a cheesecloth or other mesh bag. Secure ends.
    • Drop vegetable bag in boiling water, making sure water covers the vegetables. Shake bag so hot water reaches all pieces.
    • Start timing as soon as vegetables are in boiling water. Adjust heat to ensure continuous boiling.
    • Heat for recommended length of time.
    • Drop bag in very cold water to cool (same time as blanched).
    • Drain on paper towel or cloth.
  5. Place foods in a single layer on drying trays and start the drying process.

How to Determine Dryness of Fruits and Vegetables

Drying times will differ depending on the moisture of the product and the drying method used. Vegetables should be dried until brittle or crisp. At this stage only 10 percent of moisture remains.

Fruits should be dried until they have about 20 percent of moisture left. They should not be brittle, nor should they be sticky or tacky. It should not stick to itself when folded in half. Berries, however, should rattle when shaken. After drying, cool the fruit 30 to 60 minutes before packaging. To reduce the risk of mold growth, condition the fruit.

Conditioning Fruit

The remaining moisture in fruit may not be evenly distributed among all pieces. To equalize the moisture, fruits should be conditioned. To do this, pack the dried fruit loosely in plastic or glass jars, seal and let stand for 7 to 10 days. Shake the jars daily, and check for condensation. If condensation develops, return the fruit to the dehydrator and continue drying. Conditioning allows the excess moisture in some pieces be absorbed by some of the drier pieces. After conditioning, package the fruit appropriately.