History

Dehydrating is one of the oldest methods of food preservation known to civilization. Primitive people dehydrated or dried grasses, herbs, roots, berries, and meats by setting them out in the sun. They learned that dehydrated or dried apple supplies allowed them to exist during the long, bitter winters when food was scarce or non-existent. The light weight and high nutritional value of dried food also enabled early people to travel greater distances to hunt and explore.

The earliest written record of food drying came from the Mediterranean area, where the fishing people used to dry their catches of fish in the open air. Sun drying tea leaves was very common among the early Chinese. During Columbus’s time of travel, dehydrated food played an important part in sustaining his crew and preventing any outbreak of nutritional diseases like scurvy and beriberi. This food was excessively salted and unpalatable to us, but to them this food provided sustenance to make long sea voyage possible. American Indians preserved their produce by drying it in the sun. Fruits like apples, pears, and peaches; vegetables like corn, and meats like elk, deer, bear, and buffalo were all dehydrated and stored for the leaner months. In 1795, the French developed the first dehydrator—a device designed to regulate the drying conditions and generally speed up the food-saving process. This device, quite simple compared to our models of today, successfully dried fruits and vegetables at a controlled heat of approximately 130ºF with a continuous circulating air flow—the necessary conditions for any dehydrating operation. It was many years later before the first true dehydrator was introduced to the West.

What is Dehydration?

For dehydration to take place you must meet two basic conditions:

1. Heat—enough to draw out moisture, and
2. Air circulation—to carry the moisture off and evaporate it. To dehydrate most effectively, the air should be able to absorb the released moisture.

There are other ways of preserving foods. Freezing and canning are popular. However, unlike those methods, dehydration does not kill or cause deterioration of enzymes. Enzymes are the chemical properties found in all living things that control the growth cycle, causing them to mature and/or ripen. Dehydration suspends the action of these enzymes, putting them into a state of inactive or suspended animation until the food is rehydrated, when water is added.

What Type of Food Can be Dehydrated?

Fruits and vegetables are among the easiest and most popular for the beginner. BUT, only top quality food should be dried. Select fresh, firm, and perfectly clean food, free of bruises and blemishes. Fruits and vegetables at their peak of ripeness will have the richest flavour and be more nutritious. Immature fruit will lack colour, over-mature fruits will be soft and mushy, and over-mature vegetables will be tough and woody. Quality in, quality out. In addition to fruits and vegetables, meats, fish, herbs, cheeses, yogurt, and even pickles can be dried at home.

What is the Nutritional Value of Dehydrated Food?

Fresh produce, which can be dehydrated immediately, is our best source of natural vitamins, sugars, and minerals. Once it is harvested, some of this nutritional value is lost. If fresh food is left to set on a counter in a store or at home, the vitamin content deteriorates even further. By drying food rather than holding it fresh, most losses can be checked. With dehydrating, you preserve more nutrients than with methods of preservation that involve cooking food. The higher the temperature is during processing, the more nutrients are lost. Although dehydration requires heat, it is usually less than 145ºF. The effect of water removal on nutritional changes of dehydrated food is minimal except that some vitamin A and vitamin C are lost during dehydration (this can be kept to a minimum with pre-treatment). Properly handle, store, and prepare your foods for maximum nutrition, and consume within one year.

How Food is Dehydrated

Sun drying, air and shade drying, solar drying, oven drying, and electric dehydrator drying.

Pre-treatment

At one time, pre-treating was a standard food drying procedure. Modern dehydrators have reduced pre-treating to an “optional measure.” The fast drying times and controlled conditions dry food before it has a real chance to spoil, you’re dealing with hours of drying time rather than the days involved with older methods. It is true that some foods will keep without pre-treating and others will rapidly deteriorate in colour, flavour, texture, and nutrients. Overall, it is reasonable to say that fruits and vegetables do make better dried products if some form of pre-treatment is used. Fruits are normally eaten in the dried state, so appearance is something to consider. Certain ones, like apples, darken to a rusty brown colour during drying. Pre-treating lessens the browning, while helping to preserve vitamins C and A. For vegetables, pre-treating decreases the chances of deterioration and increases quality and storage life, and also inactivates spoilage bacteria. Unblanched vegetables are often tough and strong flavoured and blanched ones are more tender and tasty. Most pre-treatments, with the exceptions of pure steam and natural fruit juice, impart at least some additives to the dried food. Four methods of pre-treatment are: dipping, blanching, sulfuring, and microwaving.

Drying Temperatures

Herbs—95ºF, raw and living foods—105ºF, raising bread—110ºF, making yogurt—115ºF, vegetables—125ºF, fruits—135ºF, leather and fruit rolls—135ºF, meat and fish—155ºF, jerky—155ºF. When doing fruits and vegetables together, compromise with 130ºF because the moist fruit will prevent the vegetables from case hardening.

Testing

Testing is achieved through look, feel, and taste. Remove several pieces from the trays and allow to cool. When cut through the centre, there should be no visible signs of moisture. Better to over dry than under dry. Fruit generally can be considered dry when no moisture can be squeezed from a piece of it when cut; when it has become rather tough and pliable; and when a few pieces squeezed together fall apart when the pressure is released. Leathery, suede-like, and springy are descriptions you’ll see in the individual instructions for fruit. Several others, such as figs and cherries also are slightly sticky. Vegetables are generally brittle or tough-to-brittle when they’re dry enough; corn and peas will shatter when hit with a hammer. A few vegetables like tomatoes are leathery to the touch.

Packaging and Storage

Do not package warm food, but package soon after it cools before moisture is allowed to settle on food.

Use clean safe food containers.

Dehydrated food should be stored in a cool, dark, dry location; food stored at 50º–60ºF retains more food value than when it is stored at higher temperatures. The absence of light in the storage area preserves colours and vitamins.

Basements make good storage spots, but never store directly on the concrete floor or against a wall; need air flow.

Subbing Dehydrated Foods in Cooking

When substituting dehydrated vegetables or fruit in recipes that call for fresh produce, only rehydrate as much of the vegetables or fruit as it needed. In most recipes, you need only sub 1-1/2 to 2-1/3 cup of fresh vegetables.

Fresh Produce Dry Equivalents

1 onion 1/4 cups dried minced onion
or 1-1/2 tbsp onion powder
1 green pepper 1/4 cup green pepper flakes
1 cup carrots 4 tbsp powdered carrots or 1/2 cup (heaped) dried carrots
1 medium tomato 1 tbsp powdered tomato
20 pounds tomatoes 18 ounces dried sliced tomatoes

RECIPES

The following recipes are made using an electric dehydrator with “drying” sheets over top of the trays; kind of like teflon sheets—we LOVE our Excalibur Dehydrator!—recipes that are pureed, liquid, or sticky work best on the sheets whereas drying tomatoes and apples you can just use the dehydrator trays.

Banana Bread Walnut Bites

4 cups Walnuts/Pecans
3 ripe bananas
1/4 cup honey
tsp cinnamon
1 pinch salt
1/2 cup raisons
1/2 cup coconut

Place nuts in medium size bowl. Blend the banana, honey, cinnamon, and salt. Pour mixture into bowl with nuts. Stir. Dehydrate at 125ºF for at least 12–18 hours. For best results transfer the bites from the “drying sheets” onto the trays for the last few hours.

Ensure everything is well separated on the drying sheets for optimal drying.

Pumpkin Pie Bark

15 ounce can pumpkin (or fresh from your garden)
1/4 cup real maple syrup
2 teaspoon pumpkin pie spice

Stir in bowl. Pour onto sheets. 135ºF for 8–9 hours. Flip sheets halfway through.

Apple Fruit Leather (real fruit rollups!)

Take apples of your choice (we love using our Rescue Crab Apples) and wash and core. Puree using vita mix (for optimum results) or blender of your choice, then pour onto sheets and dehydrate at 145ºF for approximately 8 hours. When done, they should “peel” off.

References:
Preserve It Naturally—The complete guide to food dehydration, Third Edition, Excalibur Dehydrator Manual
Food Drying with an Attitude—A fun and fabulous guide to creating snacks, meals, and crafts, Mary T. Bell

Stacey Tress is a Holistic Nutritional Therapist at Garden Therapy Yorkton. For more recipe ideas and/or to learn more about Stacey and Garden Therapy, please visit them on Facebook “Garden Therapy Yorkton” or their webpage at www.gardentherapyyorkton.ca, email: stacey.gardentherapy@gmail.com, or call (306) 782-1613 or (306) 641-4239.