Learning how to dehydrate food is simple, safe and easy. Drying food is also a great way to eat healthy and to save on your overall food costs.
If you would like to preserve fruits and vegetables from your garden or the produce from your local farmers market... then dehydrating food may be the right method for you!
With emergency and survival preparedness in mind, dehydrating food has a number of advantages:
2. Oven Drying
Drying removes the moisture from the food so bacteria, yeast and mold cannot grow and spoil the food. Drying also slows down the action of enzymes (naturally occurring substances which cause foods to ripen), but does not inactivate them.
In drying, warm temperatures cause the moisture to evaporate. Low humidity allows moisture to move quickly from the food to the air. Air current speeds up drying by moving the surrounding moist air away from the food.
Because drying removes moisture, the food becomes smaller and lighter in weight. When the food is ready for use, the water is added back, and the food returns to its original shape.
How To Dehydrate Food 4 different ways:
All of these methods work by using the right combination of warm temperatures, low humidity and air current. We will discuss these options below:
A food dehydrator is an electrical appliance made for drying food indoors. A dehydrator has an electric element for heat with a fan and vents for air circulation. Dehydrators should be efficiently designed to dry foods quickly at 140°F.
How To Dehydrate Food in 10 Simple Steps:
1. Read the owners manual. (Its amazing how many people DON'T do this when they purchase a product)
2. Start with fresh fruits and vegetables of the very best quality. Over-ripe, bruised and otherwise deteriorated produce will not yield good results when dehydrated.
3. Clean, hull and slice all fruits and vegetables, taking care to maintain consistency in the thickness of the slices. (This will ensure that everything dries at an even rate.)4. If desired, treat apples, pears and other fruits prone to oxidation with citrus juice or ascorbic acid. This will help to retain the color of the fruit before, during and after the drying process.
5. Blanche broccoli, cauliflower, celery, carrots, corn, peas and potatoes to speed drying time and to help maintain color. Three to five minutes in boiling water should be adequate.
(*See detailed step on blanching vegetables below)
6. Optional: Add salt, sugar or spices to flavor.
7. Now, load your fruit and vegetable slices onto the dehydrator trays, being careful not to overlap them, as this will slow the drying time.
8. Turn your dehydrator on immediately after loading to start the dehydration process. Consult the owner's manual for recommended drying times, but expect the process to take between 8-12 hours on average.
9. As you reach the end of the drying time, check your fruits and vegetables frequently for dryness. To do so, simply remove a slice from the dehydrator, allow it to cool and then feel it with your fingers. If the slice feels dry to the touch, it should be adequately dried.
To further evaluate the dryness of fruit: cut several fruit slices in half, and check the cut edges for moisture beads. If any are present, the fruit is not yet dry enough, and needs to be returned to the dehydrator.
10. Package and store your dehydrated food.
(* Go to the Packaging, Storing and Using Dried Foods section below for detailed instructions)
Tips On What To Check For:
How To Dehydrate Food by Oven Drying
Everyone who has an oven can learn how to dehydrate food. By combining the proper factors of heat, low humidity and air flow, an oven can be used as a dehydrator.
An oven is ideal for occasional drying of meat jerky, fruit leathers, banana chips or for preserving excess produce like celery or mushrooms.
Because the oven is needed for every day cooking, and the excessive use of electricity or fuel, it may not be satisfactory for preserving abundant garden produce.
Oven drying is slower than using a dehydrator because it does not have a built-in fan for the air movement. (However, some convection ovens do have a fan).
It takes about two times longer to dry food in an oven than it does in a dehydrator. Thus, the oven is not as efficient as a dehydrator and uses more energy.
Using Your Oven -
CAUTION: This is not a safe practice for a home with small children.
First, check the dial and see if it can register as low as 140°F. If your oven does not go this low, then your food will cook instead of dry. Use a thermometer to check the temperature at the "warm" setting. For air circulation, leave the oven door propped open two to six inches. Circulation can be improved by placing a fan outside the oven near the door.
Because the door is left open, the temperature will vary. An oven thermometer placed near the food gives an accurate reading. Adjust the temperature dial to achieve the needed 140°F.
Drying trays should be narrow enough to clear the sides of the oven and should be 3 to 4 inches shorter than the oven from front to back. Cake cooling racks placed on top of cookie sheets work well for some foods. The oven racks, holding the trays, should be two to three inches apart for air circulation.
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How To Dehydrate Food Using The Sun
The high sugar and acid content of fruits make them safe to dry in the sun. Herbs are also safe and do well when dried in the sun.
NOTE: Vegetables and especially meats are not recommended for sun drying.
Vegetables are low in sugar and acid. This increases the risks for food spoilage. Meats are high in protein making them ideal for microbial growth when heat and humidity cannot be controlled.
To dry in the sun, hot, dry, breezy days are best. A minimum temperature of 86°F is needed with higher temperatures being better. It takes several days to dry foods out-of-doors. Because the weather is uncontrollable, sun drying can be risky. Also, the high humidity in the South is a problem. A humidity below 60 percent is best for sun drying.
Fruits dried in the sun are placed on trays made of screen or wooden dowels. Screens need to be safe for contact with food. The best screens are stainless steel, Teflon coated fiberglass or plastic.
Avoid screens made from "hardware cloth." This is galvanized metal cloth that is coated with cadmium or zinc. These materials 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.
Place trays on blocks to 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.
Cover the trays with cheesecloth to help protect the fruit from birds or insects. Fruits dried in the sun must be covered or brought under shelter at night. The cool night air condenses and could add moisture back to the food, thus slowing down the drying process.
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How To Dehydrate Food By Solar Drying
Recent efforts to improve on sun drying have led to using homemade solar drying units. Using a solar drying unit also uses the sun as the heat source.
Below is a picture of a typical homemade solar food dehydrator.
A foil surface inside the dehydrator helps to increase the temperature. Ventilation speeds up the drying time. Shorter drying times reduce the risks of food spoilage or mold growth. Follow the same food drying guidelines as the other methods.
As you can see, learning how to dehydrate food using the solar method requires a little creativity if using a homemade solar food dryer.
Pasteurization of Certain Sun or Solar Dried Foods
Sun or solar dried fruits and vine dried beans need treatment to kill any insect and their eggs that might be on the food. Unless destroyed, the insects will eat the dried food. There are two recommended pasteurization methods:
1. Freezer Pasteurization - Seal the food in freezer-type plastic bags. Place the bags in a freezer set at 0°F or below and leave them at least 48 hours.
2. Oven Pasteurization - Place the food in a single layer on a tray or in a shallow pan. Place in an oven preheated to 160°F for 30 minutes. After either of these treatments the dried fruit is ready to be conditioned and stored.
Dried fruits are unique, tasty and nutritious... when learning how to dehydrate food, you will begin by washing the fruit and coring or removing pits if needed. Fruits can be cut in half or sliced. Some can be left whole. Thin, uniform, peeled slices dry the fastest. The peel can be left on the fruit, but un-peeled fruit takes longer to dry. Apples can be cored and sliced in rings, wedges, or chips. Bananas can be sliced in chips or sticks.
Fruits dried whole take the longest to dry. Before drying, skins need to be "checked" to aid speed drying. To "check" the fruit place it in boiling water and then in cold water. Because fruits contain sugar and are sticky, spray the drying trays with nonstick cooking spray before placing the fruit on the trays. After the fruit dries for one to two hours, lift each piece gently with a spatula and turn.Pre-treating the Fruit
Ascorbic Acid - Ascorbic acid (vitamin C) mixed with water is a safe way to prevent fruit browning. Ascorbic acid is available in the powdered or tablet form, from drugstores or grocery stores. One teaspoon of powdered ascorbic acid is equal to 3000 mg of ascorbic acid in tablet form. (If you buy 500 mg tablets, this would be six tablets).
Directions for Use - Mix 1 teaspoon of powdered ascorbic acid (or 3000 mg of ascorbic acid tablets, crushed) in 2 cups water. Place the fruit in the solution for 3 to 5 minutes. Remove fruit, drain well and place on dryer trays. After this solution is used twice, add more acid.
Fruit Juice Dip - A fruit juice that is high in vitamin C can also be used as a pretreatment, though it is not as effective as pure ascorbic acid. Juices high in vitamin C include orange, lemon, pineapple, grape and cranberry. Each juice adds its own color and flavor to the fruit.
Directions for Use - Place enough juice to cover fruit in a bowl. Add cut fruit. Soak 3 to 5 minutes, remove fruit, drain well and place on dryer trays. This solution may be used twice, before being replaced. (The used juice can be consumed.)
Drying the Prepared Fruit
Whichever drying method you choose when learning how to dehydrate food, whether it's: sun drying, solar drying, oven drying or dehydrator drying, be sure to place the fruit in a single layer on the drying trays. The pieces should not touch or overlap.
Follow the directions for the drying method you choose and dry until the food tests dry. Approximate drying times are given below. Food dries much faster at the end of the drying period, so watch it closely.
Determining Dryness of Fruits
Since dried fruits are generally eaten without being re-hydrated, they should not be dehydrated to the point of brittleness. Most fruits should have about 20 percent moisture content when dried.
To test for dryness, cut several cooled pieces in half. There should be no visible moisture and you should not be able to squeeze any moisture from the fruit. Some fruits may remain pliable, but are not sticky or tacky.
If a piece is folded in half, it should not stick to itself. Berries should be dried until they rattle when shaken. After drying, cool fruit 30 to 60 minutes before packaging. Packaging food warm can lead to sweating and moisture buildup. However, excessive delays in packaging could allow moisture to re-enter food.
When dried fruit is taken from the dehydrator or oven, the remaining moisture may not be distributed equally among the pieces because of their size or their location in the dehydrator. Conditioning is a process used to equalize the moisture and reduce the risk of mold growth.
To condition the fruit, take the dried fruit that has cooled and pack it loosely in plastic or glass jars. Seal the containers and let them stand for seven to ten days.
The excess moisture in some pieces will be absorbed by the drier pieces. Shake the jars daily to separate the pieces and check the moisture condensation. If condensation develops in the jar, return the fruit to the dehydrator for more drying. After conditioning, package and store the fruit.
*Remember, if you have dried fruits or vine dried beans in
the sun, they must be pasteurized to kill any insects and their eggs
that might be on the food before they are packaged.
(See pasteurization step above)
In learning how to dehydrate food, it's important to know the different methods of drying fruits versus drying vegetables:
Vegetables contain less acid than fruits, vegetables are dried until they are brittle. At this stage, only 10% moisture remains and no microorganism can grow.
To prepare vegetables for drying, wash in cool water to remove soil and chemical residues. Trim, peel, cut, slice or shred vegetables. Remove any fibrous or woody portions and core when necessary, removing all decayed and bruised areas. Keep pieces uniform in size so they will dry at the same rate. A food slicer or food processor can be used. Prepare only as many as can be dried at one time.
Blanching is a necessary step in preparing vegetables for drying. By definition, blanching is the process of heating vegetables to a temperature high enough to destroy enzymes present in tissue. Blanching stops the enzyme action which could cause loss of color and flavor during drying and storage. It also shortens the drying and re-hydration time by relaxing the tissue walls so moisture can escape and later re-enter more rapidly.
Vegetables can be water blanched or steam blanched. Water blanching usually results in a greater loss of nutrients, but it takes less time than steam blanching.
Water Blanching - Fill a large pot 2/3 full of water, cover and bring to a rolling boil. Place the vegetables in a wire basket or a colander and submerge them in the water. Cover and blanch according to directions. Begin timing when water returns to boiling. If it takes longer than one minute for the water to come back to boiling, too many vegetables were added. Reduce the amount in the next batch.
Steam Blanching - Use a deep pot with a tight fitting lid and a wire basket, colander or sieve placed so the steam will circulate freely around the vegetables. Add water to the pot and bring to a rolling boil. Place the vegetables loosely in the basket no more than 2 inches deep. Place the basket of vegetables in the pot, making sure the water does not come in contact with the vegetables. Cover and steam according to the directions.
Cooling and Drying the Prepared Vegetables
After blanching, dip the vegetables briefly in cold water. When they feel only slightly hot to the touch, drain the vegetables by pouring them directly onto the drying tray held over the sink. Wipe the excess water from underneath the tray and arrange the vegetables in a single layer.
Then place the tray immediately in the dehydrator or oven. The heat left in the vegetables from blanching will cause the drying process to begin more quickly. Watch the vegetables closely at the end of the drying period. They dry much more quickly at the end and could scorch.
Determining Dryness of Vegetables
Vegetables should be dried until they are brittle or "crisp." Some vegetables would actually shatter if hit with a hammer. At this stage, they should contain about 10 percent moisture.
Because they are so dry, they do not need conditioning like fruits.
Knowing how to dehydrate food also requires knowledge of how to store and use the foods:
After foods are dried, cool them completely. Then package them in clean moisture-vapor-resistant containers. Glass jars, metal cans or freezer containers are good storage containers, if they have tight-fitting lids. Plastic freezer bags are acceptable, but they are not insect and rodent proof. Place the fruit in a plastic bag before storing it in a metal can.
Dried food should be stored in a cool, dry, dark place. Most dried fruits can be stored for 1 year at 60° F, 6 months at 80° F. Dried vegetables have about half the shelf-life of fruits.
Fruit leathers should keep for up to 1 month at room temperature. To store any dried product longer, place it in the freezer.
USING DRIED FOODS
Dried fruits can be eaten as is or reconstituted. Dried vegetables must be reconstituted. Once reconstituted, dried fruits or vegetables are treated as fresh.
To reconstitute dried fruits or vegetables, add water to the fruit or vegetable and soak until the desired volume is restored. Do not over-soak the food. Over-soaking produces loss of flavor and a mushy, water-logged texture.
For soups and stews, add the dehydrated vegetables without re-hydrating them. They will rehydrate as the soup or stew cooks. Also, leafy vegetables and tomatoes do not need soaking.
Add enough water to cover and simmer until tender. CAUTION! If soaking takes more than 2 hours, refrigerate the product for the remainder of the time.
Follow this link for dehydrated food recipe ideas.
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Credits: How To Dehydrate Food Page
(Some content on the "How To Dehydrate Food" page was extracted from "So Easy to Preserve", 5th ed. 2006. Bulletin 989, Cooperative Extension Service, The University of Georgia, Athens. Revised by Elizabeth L. Andress. Ph.D. and Judy A. Harrison, Ph.D., Extension Foods Specialists.)
(Some content from the "10 steps for food dehydrators" was derived from: about.com)