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Drying Fruits and Vegetables

Theo Thomas and Holly Berry

INTRODUCTION

Drying is the oldest known method of preserving food. Historically, food was dried in the sun.

Nowadays, we can sun dry or dry in an oven or a dehydrator that is especially designed for home

drying.

Drying has many advantages. It is safe. By removing most of the moisture from a food,

microorganisms can't grow in it. Dried food is compact so that less storage space is needed. Plus,

dried foods keep well, travel well and add variety to our diets.

For more information, refer to publication PNW0397, "Drying Fruits and Vegetables."

TERMS YOU SHOULD KNOW

RECONSTITUTING - restoring moisture to a dried food. Properly dried foods return to

approximately their original size, form and appearance.

SULFITE SOLUTION - solution of 1 water and sodium sulfite, sodium bisulfite or sodium

metabisulfite. Soaking fruit 10 minutes in this solution effectively prevents changes in color,

flavor and nutrition. Sulfite-sensitive people should choose another pretreatment.

SULFURING FRUIT - pretreating fruits with the fumes of burning sulfur. This method is done

outdoors in a partially ventilated container and effectively maintains food quality. Sulfite-

sensitive people should choose another pretreatment.

WHAT TO DRY

Fruits and vegetables selected for drying should be of the highest quality -- fresh and ripe.

Drying does not improve the quality. Immature produce will lack flavor and color. Overmature



produce may be fibrous or mushy. If the food is not perfect for eating, it is not suitable for

drying.

PNW0397, "Drying Fruits and Vegetables" gives directions for the most commonly dried foods.Any fruit or vegetable can be safely dried, but some of them just don't taste good dried.

DRIED VEGETABLES can be used as chips, reconstituted for a cooked side dish, used in soups,

stews, casseroles and stuffings or made into powders. (To powder: use very dry vegetables and

put only one-half cup at a time in a blender.) DRIED FRUITS tend to be chewy and make

delicious snacks. Pieces of dried fruits are good in cookies, muffins, cakes and breads. They can

also be reconstituted and used in sauces, pies or cobblers or added to gelatin salads, cooked

cereals and ice cream.

For information on reconstituting dried fruits and vegetables, see page 26 in PNW0397.

NUTRITIONAL CHANGES DURING DRYING

Fresh fruit and vegetables provide us with bulk, energy, minerals and vitamins. Bulk is provided

by the indigestible fiber and energy is provided by the carbohydrates and protein. Neither bulk

nor energy is lost in the drying process. During blanching, a small portion of the vitamin C may

be lost by leaching. The amount varies depending on the care taken in blanching. To keep

leaching to a minimum, blanch only as long as required. Do not under-blanch, however, because

then the food's enzymes will still be active, reducing the quality. Pretreating light-colored fruits

helps protect against loss of vitamins A and C.

To avoid nutrient losses during drying, follow these guidelines. Use proper pretreatments (see

PNW0397). Dry food quickly at a maximum of 150°F with good air circulation and lowhumidity. Eat the dried food as soon as possible. Store a maximum of 6 months to 1 year in

airtight containers.

Nutrients are concentrated in dried food, compared to fresh on a per pound basis. But you need

to eat an amount equal to the fresh to get the same nutrition (2 fresh apricots = 4 dried halves).



The most effective pretreatment is "sulfuring." Prepared fruit is exposed to fumes of burning

sulfur. This must be done outdoors. Detailed instructions are found in PNW0397.

Indoor pretreatments include dipping the cut fruit in sulfiting solutions, ascorbic acid solution, or syrup blanching. These methods are not as effective as sulfuring, but may be used by people who

are sulfite-sensitive. Check in PNW0397 for instructions.

CAUTION: Sulfur dioxide and sulfiting agents, like sodium sulfite, sodium bisulfite and sodium

metabisulfite, are hazardous to the health of a small group of people. It is estimated that 5% of

asthmatics are sensitive to sulfites, and an unknown number of nonasthmatics. The symptoms are

sudden attacks of asthma, difficult breathing, nausea, diarrhea and even death. Persons who are

sulfite-sensitive should not use any sulfur-containing products to pretreat fruit before drying, and

should not eat food treated with sulfur.

EQUIPMENT AND METHOD

You can satisfactorily dry produce wherever you have a fairly constant temperature (as close to

140°F as possible), low relative humidity and circulating air.

Products dried in controlled heat generally are superior to sun-dried ones in color, flavor,

cooking quality and nutritive value. Oven or dehydrator dried foods will also be free of insects.

However, controlled heat drying requires additional equipment and operating expenses.

Consider the following factors in choosing the method best for you.

SUN DRYING depends on the weather, the temperature and relative humidity outside. If you

live in a hot, dry climate, sun drying may be successful. Its advantage is the cost. The only

investments are drying trays, netting to protect against insects and the food itself. Its main

disadvantage is time. What would take 6 to 10 hours to dry using another method may take 3 to 5

days in the sun. To avoid scorching, move the food into the shade to finish when it is about two-

thirds dry.



SOLAR DRYING is like sun drying only better. You are still dependent on the weather but the

sun's rays are concentrated so drying time is shortened. The back window of a car with the

windows open slightly to allow air flow is an example. You may wish to build a solar oven.

OVEN DRYING is small-scale drying. It's a good choice if you want to dry only 4 to 6 pounds

of produce at a time. Disadvantages are the cost of the energy and having the oven on constantly.

Oven drying takes 2 or 3 times longer than a dehydrator. You must rotate and shift trays every

half hour and turn the food occasionally to assure even drying. To avoid scorching food, turn off

the heat when drying is almost completed and open the oven door wide.

DEHYDRATOR DRYING is a more reliable method. Dehydrators should have a heat source,thermostat and some method of air circulation. They can be purchased or made. When selecting

a dehydrator consider:

- Capacity -- drying area in square feet (each square foot holds about 1 pound produce); adequate

size for family needs; easy to handle and move.

- Construction -- sturdy, safe and durable (metal and high-grade plastic are superior to wood for safety, durability and cleaning; wood eventually dries, absorbs odors and warps); double-wall

construction to cut heat loss; convenient to load and unload; adequate venting; easy to clean;

trays slide in and out easily; trays are food-safe plastic, stainless or nylon; trays have durable

mesh and are replaceable.

- Operating parts -- constant heat source; heating element enclosed; parts easy to replace; wattage

adequate and suitable for average circuit; temperature dial easy to read; dial easy to adjust; fan

for even air distribution that is quiet and durable.

- Economy -- cost per square foot of drying area; a model with lowest cost per square foot may

not be economical if it doesn't hold enough; electricity use.



- Safety -- nonflammable construction; enclosed, properly wired electrical components; nontoxic

finishes; warranty; repair location; no sharp edges or corners; instructions for use and

maintenance.

OTHER APPLIANCES , such as some forced convection ovens (with drying trays as optional

accessories), may be used for food drying. Foods can be dried in a convection microwave; it's the

convection cycle, not the microwaves, that actually dry the food. Read the directions that come

with those ovens for more information.

Fruits, vegetables and meats should not be dried in a microwave for two reasons: 1. The oven

door must be open for moisture to escape. A microwave can only be operated with the door shut;and 2. Drying times vary. Foods can become so dry they ignite and burn out the magnetron tube.

TRAYS

You can make your own drying trays. They should be made of a food-safe material that allows

good air circulation

Use:

Stainless steel screening

Aluminum screens

Food-grade plastic mesh

Cheesecloth or nylon netting



Wood slats (wood free of pitch and odors)

Avoid:

Galvanized screening

Zinc and cadmium-coated screens

Copper screening

Fiberglass (unless teflon coated)

Cheesecloth used in a gas oven

Screens may sag; construct the trays to allow restretching netting or screening periodically.

If the food sticks, spray the tray with a no-stick vegetable spray.

TEST FOR DONENESS

Remove a few pieces to test and let them cool. Fruit should be pliable and leathery. Squeeze a

few in your hand and see if they spring apart. Tear one open and see if it is dry inside.

Vegetables should be hard and brittle. They should shatter when hit with a hammer. Remove

enough moisture to prevent mold growth during storage, but do not over-dry. If you prefer to dry

your foods moister than recommended, freeze the dried food for safer storage.

FRUIT & VEGETABLE LEATHER



Wash and cut away blemishes. Remove pits from fruit. In most cases seeds and peel need not be

removed.

Cut food into chunks. Heat in saucepan with a little water if needed to soften it up and make asmoother texture.

Add food to blender gradually until it is a smooth puree. Watery puree can be concentrated by

cooking over low heat until the mixture thickens.

Flavoring the puree is up to you. To sweeten add sugar or honey to taste. Spices like cinnamon,

nutmeg and mint are good with fruits, while onion powder, marjoram or basil are good with

vegetables. Add one flavoring at a time in small amounts and taste. When the puree is dried, the

spices and flavoring will concentrate so use them sparingly. If the puree is too strong add more

fruit or vegetable. Add 1 tablespoon lemon juice per 2 cups puree to help preserve natural color

in light-colored fruits.

When you have a tasty puree, pour it out onto a cookie sheet lined with plastic wrap. (Tape the

wrap to the edges.)

Spread the puree around so that it is about 1/4-inch thick. If desired, you can garnish it with

coconut, nuts, sesame or sunflower seeds sprinkled lightly on top.

Dry by using one of the drying methods discussed previously. Generally, it will dry in 4-10 hours

in the oven or dehydrator and from 1 to 3 days in the sun.

Properly dried leather will be slightly sticky to the touch but will peel readily from the plastic.

Loosely roll up the leather and then wrap it in plastic wrap or put in an airtight bag or container.

For best quality, use within 3 months when stored at room temperature, 6 months in the

refrigerator or within a year if frozen.



Use leathers in lunches, for camping, or when traveling. Spread with peanut butter, cream

cheese, cheese spread or melted chocolate. Roll 2 fruit leathers together. Make into a beverage

by combining 5 parts water with 1 part leather in a blender. Crumble vegetable leathers into

soups for concentrated flavor.

HOW TO DRY HERBS

By growing and drying your own herbs, you will always have a fresh inexpensive supply close.

For people on salt-free diets, herbs enhance the flavor of otherwise bland foods.

Harvest young tender leaves. They are more flavorful and aromatic than older leaves. Rinse

gently in cool water and drain well on paper towels.

Hang dry herbs with long stems (savory, rosemary, sage, mint and marjoram). Tie stems together

in small bunches. Hang upside down in a warm, dry, airy place, but not in the sun. Allow 5 to 10

days to dry. Store dry leaves in airtight containers.

Dry seeds and herbs with short stems on trays. Spread seeds or leaves in a single layer on a

cookie sheet. Dry in a warm, airy place 4 to 6 days or dry in 140° F oven 1-4 hours.

Herbs can also be dried in a microwave because the leaves contain little moisture and dry

rapidly. Place a single layer of herb leaves between paper towels. Dry them for 1 to 2 minutes in

the microwave, depending on the thickness of the leaves. Cool and test for brittleness. When the

herb leaves crumble in your hands, they are done. If leaves are not dry, microwave 1/2 to 1

minute longer.

Do not sun dry herbs. Sunlight destroys their natural aroma. Whole herbs keep their flavor longer

than crushed or ground herbs.



Use 1/3 as much dried herbs as you would fresh. Store in dark, cool, dry place in airtight

containers for up to 1 year, or freeze.

DRYING SUNFLOWER SEEDS

Select sunflowers with dry stalks. Remove seeds. If plants were sprayed, wash the seeds and pat

dry. Spread on cheesecloth or screening. Dry in a warm place for at least a week. An alternate

method is to hang the flowers in a cool, dry place for a month or until the seeds pop out. Tie a

cloth or mesh bag around the flower to catch seeds that fall. The seeds must be thoroughly dry.

To toast the seeds, measure 4 cups seeds and 1/2 cup salt into saucepan. Add water to cover.

Bring to a boil; boil 5 minutes. Drain; spread on absorbent paper to dry. Place in shallow baking

pan; bake at 325° F for 25-30 minutes, stirring occasionally. Cool thoroughly. Store in a dry

place in an airtight container like a plastic bag or glass jar. One flower makes about 3 cups of

seeds.

OTHER FOODS TO DRY

Bananas - Cut in 1/4-inch thick slices. Dip into orange juice, pineapple juice or lemon juice. Dry

until leathery or until crisp, whichever you prefer.

Melon - All varieties can be dried and will taste much sweeter when dried. Remove rind and

seeds. Cut into 1/4-inch thick slices about 2 inches long. Dry 6-16 hours in a dehydrator until

pliable. The pieces may be slightly sticky.

Celery - Wash and cut stalks into 1/2-inch pieces. Steam 2 minutes. Dry until brittle. Best used in

soups.

Mushrooms - Clean and slice. Arrange in thin layer on trays. Dry until leathery.



Horseradish - Wash and peel or scrape roots. Grate or cut into 1/8 inch slices. Dry until very

brittle and powdery.

QUESTIONS AND ANSWERS

HOW LONG WILL IT TAKE TO DRY PEACHES?

Drying times vary widely, depending on the drying method, the temperature, quantity and

relative humidity. Fruits and vegetables also vary in moisture content from one batch to another.

That's why drying charts give you a range, such as 4 to 16 hours. Test for dryness frequently.

WHERE SHOULD DRIED FOODS BE STORED?

Store dried foods in a dry, cool, dark place. The higher the temperature, the shorter the storage

time. Recommended storage times range from 6 months to 1 year. You can freeze dried foods to

assure longer storage time and protect against mold. Use clean, dry, insect-proof,

moisture/vaporproof containers and package in small amounts to avoid constantly opening a

container and exposing it to air.

I OVERDRIED MY FRUIT AND IT'S HARD AND BRITTLE, NO ONE WILL EAT IT. CAN

IT BE SAVED?

Don't despair. You can blend, chop or break it into tiny pieces and use it over cereal or ice cream.

Or, you could try tenderizing it by putting it in boiling water for about 15 seconds.

I CHECKED MY DRIED FRUIT AND FOUND MOISTURE ON THE INSIDE OF THE

JARS. THERE WAS NO SIGN OF MOLD. WHAT SHOULD I DO? DRY MORE?

Spread it on trays in a 150°F oven for 30 minutes. Cool and repack. Or, you could freeze it.

Foods that seem bone dry when packaged often reabsorb moisture during storage.

WHERE CAN I FIND ELEMENTAL SULFUR (USP) TO USE IN SULFURING FRUITS

BEFORE DRYING?



Sulfur may be purchased at your local pharmacy. Get a pure form of sulfur. It also may be called

flowers of sulfur or sublimed sulfur. Garden dusting sulfur is not suitable. Do not use it in

solution.

I DID NOT PRETREAT MY PEARS BEFORE DRYING AND NOW THEY ARE DARKER.

ARE THEY DANGEROUS TO EAT?

No, the fruit is still good to eat. Next time try soaking them for 10 minutes in 1 to 2 tablespoons

of sodium sulfite in 1 gallon of water. Drain well. If you're sensitive or allergic to sulfites, you

can use a saline solution or ascorbic acid solution. Directions are available in PNW0397.

However, while these solutions prevent browning during preparation, they do not guarantee

stability of color during drying and storage.

DOES THE CALORIE CONTENT OF FOODS CHANGE DURING DRYING?

The calorie content of foods does not change but is concentrated into a smaller mass as moisture

is removed during drying. Therefore, on a per pound basis, dried foods contain considerably

more calories than do the same foods fresh.

I FOUND SOME WILD MUSHROOMS IN MY BACK YARD. CAN I DRY THEM?

Only if they are edible varieties. The toxins of poisonous mushrooms are not destroyed by dryingor cooking. Make sure you know the difference between poisonous and edible varieties before

you start picking.

PROBLEMS

There aren't many problems in food drying. However, here are some things to watch for.

CASE HARDENING - If the drying temperature is too high or the humidity too low, the food

may harden on the surface. This makes it more difficult for the moisture inside to escape and for

the food to dry properly.



SCORCHING - When black streaks or areas appear on the food, it has scorched. This is most

common in sun drying and is why we recommend you move the food into the shade when it is

about two-thirds dry.

SOURING - If the temperature is too low at the beginning of drying or it is very humid, the food

may sour or ferment. It may even mold if conditions are too cold. Overloading the trays can also

cause this problem.

MOLD - Moldy dried food should always be discarded. Check stored dried foods frequently to

be sure they remain dry. Next time, either remove more moisture from the food or store the dried

food in the freezer.

INSECTS - All sun-dried foods should be pasteurized before storing to destroy insects or their

eggs. Heat fruit and vegetables on trays in a 150° F oven for 30 minutes or put in freezer for 48

hours. Store food in insect-proof containers.

DRYING FRUITS AND VEGETABLES CHECKLIST

1. Select fruits and vegetables in prime condition.

x

2. Pretreat, if necessary (see PNW0397 "Drying Fruits and Vegetables").

Blanch (most) vegetables

Pretreat light-colored fruits using one of the following:

Sulfur outdoors



Dip in sulfite, honey or ascorbic acid solution

Syrup blanch

x

3. Choose drying method that provides temperature of 140° F. low humidity and good air

circulation.

Solar drying

Direct sun

Solar dehydrator

Car window

Controlled heat

Oven

Electric dehydrator

Commercial dehydrator



x

4. Test for doneness.

Cool.

Fruits pliable and leathery

Vegetables hard and brittle

x

5. Package in appropriate containers.

Cool.

Condition or pasteurize, if necessary.



Use clean, dry, airtight, insect-proof containers.

x

6. Store in cool, dry, dark place.

Check occasionally for moisture.

Reheat and repackage.

Discard moldy food.

Use in 6 months to 1 year.

x

7. Freeze dried foods if slightly moist, or for long-term storage.

x

8. Prepare for eating. Eat as is. Reconstitute.



ANSWERS TO SELF-TEST

1. FALSE - If the temperature was 175° F, case hardening could occur where the outside of the

food dries hard before the inside moisture can escape. Keep the temperature around 140° F for best results.

2. FALSE - Blanching vegetables before drying destroys enzymes, not bacteria.

3. TRUE - Prop the oven door open to maintain the low temperature and let moisture escape

during drying.

4. FALSE - While foods are warm, there are moisture droplets on them. Cool first, then test to

avoid over-drying.

5. TRUE - Avoid galvanized screening as it will impart a metallic taste, can discolor vegetables

and may be toxic when acid foods are dried.

6. TRUE - All sun-dried foods should be pasteurized (heat on trays in 150° F oven for 30

minutes or put in freezer for 48 hours) before storing to destroy insects and their eggs.

7. TRUE - Check stored foods frequently to be sure they remain dry and to avoid spoilage from

mold growth.

8. TRUE - Mold is a sign of spoilage. Discard dried food with any sign of mold.

9. FALSE - Choose fruit for drying that is of the highest quality, fresh and ripe. Overripe fruits

are mushy when dried.



10. TRUE - Properly dried foods reconstitute well. They return to approximately their original

size, form and appearance and retain much of their aroma and flavor.

DRYING FRUITS AND VEGETABLES

SELF-TEST

Read each statement. If you think it is true, write a "T" in the "Before" column. If you think it's

false, write an "F." After reading and studying this publication, test yourself a second time using

the "After" column. Check the inside back cover for the correct answers. If you still have

questions, call your County Extension office.

Before

After

1. Generally, an oven or food dehydrator should be about 175° F when drying fruits and

vegetables.

2. Vegetables are blanched prior to drying to destroy bacteria.

3. When food is dried in an oven, the oven door should be propped open.

4. Test foods that are drying while they are still warm on the tray so that you don't

overdry them.

5. Galvanized screening should not be used on trays that are used in drying.



6. Pasteurizing sun-dried foods is recommended before storage to prevent spoilage.

7. Food that is packaged seemingly bone dry can spoil if moisture is reabsorbed during

storage.

8. Moldy dried food should always be discared.

9. Very ripe and overripe fruits are best for drying.

10. One test of a proper drying technique is how well the dried food reconstitutes.

Theo Thomas is an Extension Home Economist at Washington State University and Holly Berry

an Extension Home Economist at Oregon State University. Reviewed by Val Hillers, Extension

Food Specialist, Washington State University. Edited by Jill D. Whelchel. Designed by Clint

Keller.

Issued by Washington State University Cooperative Extension and the US Department of

Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension



programs and policies are consistent with federal and state laws and regulations on

nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and

sexual orientation. Evidence of noncompliance may be reported through your local Cooperative

Extension office. Trade names have been used to simplify information; no endorsement is

intended. Reprinted August 1997. Subject code 665. A. HS0005

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