University of Vermont Extension 
Department of Plant and Soil Science

Fall News Article


Dr. Leonard Perry, Extension Professor
University of Vermont
Are you getting overrun with vegetables from the garden, and wonder what to do with them?  Or, perhaps you are just looking for an easy way to preserve your produce or that from local farms and farmers' markets.  In addition to freezing, drying or dehydrating is perhaps the easiest way to preserve vegetables.  It is the oldest method, yet perhaps the least used.

Successfully drying vegetables depends on four factors:  selection of produce at peak flavor and quality, blanching to stop decomposition and ripening, proper heat and drying conditions, and proper storage.  Store cool, dry and dark as in a cellar, refrigerator, or if freezing use special freezer containers or bags made for this purpose.  Other containers and bags may not be moisture-proof, resulting in shriveling and freezer burn.  Dried vegetables, properly stored, last for 6 to 12 months.  As they aren't quite the same taste and texture as fresh, they are best used in soups, casseroles, sauces and stews.
When produce is picked, enzymes are activated that result in decomposition.  To stop these, blanching is used for many vegetables.  This is merely boiling for short periods, time varying with the crop.  Blanching by steaming, instead of boiling, will help to preserve more nutrients.  Properly blanched, vegetables will be heated through but won't be cooked.  Test a piece by cutting to see if it is cooked (translucent) nearly to the center.
An easy way to blanch is to place a quart of produce, once cleaned and washed, in the middle of a 2 or 3 foot square piece of cheesecloth.  Gather the corners and immerse in boiling water, making sure water reaches all produce in the bag.  Remove after the time suggested for each crop, immerse in cold water to cool quickly, for the same amount of time.  Then drain on cloth or paper towels.  Homebrew shops sell bags for grains that work well for this purpose too. 
When blanching, you may wish to add some citric acid to the water to prevent darkening and to kill any harmful microbes.  Use 1/4 teaspoon of citric acid to one quart of water.  Most vegetables should be blanched for about 3 to 4 minutes.  Use longer (5 to 6 minutes) for Brussels sprouts, cut corn, and potatoes. Use no blanching for herbs, onions, peppers, horseradish, and tomatoes. 
Tomatoes should be dipped in boiling water for under a minute until skins split, then cold water to loosen skins and make peeling easy.  Then slice or cut in sections, and soak for 10 minutes in one teaspoon of citric acid to one quart of water.
It is often easier to prepare vegetables as you would for cooking by cutting or slicing prior to blanching.  Corn is easier blanched, then taken off the cob.  To dry you may spread on trays in the sun, in the oven, or use a dehydrator.  If using the sun, you really need about 3 days at 90 degrees (F) or above so the produce dries without molding first.  This may be difficult in cool climates or summers. A solar method some use is to spread on trays and place in cars on the dash or back window ledges on summer days. If you get a cloudy day, though, and the produce isn't dry you may have to finish using another method to avoid spoilage.
If using an oven for drying vegetables, the key is to dry at the correct temperature: under 200 degrees (F), preferably around 140 degrees.  Some ovens may not get this low.  If too cool, produce wont dry properly or quickly enough.  If too hot, they will cook instead of merely dry.  Check every half hour to make sure the temperature is correct (an oven thermometer is useful), to allow moist air to escape, and to rotate trays for uniform drying.  Make sure produce is no more than one half-inch deep on trays, or stir often.  Keep about 2 to 3 inches between trays.
If using your own trays for drying, don't use galvanized screening as the metals in it can cause harmful reactions with acid foods.  Aluminum may corrode and discolor with use. If using these, line with cheesecloth to prevent produce from touching the metal.  Wash trays well between uses, and a light coating of spray cooking oil makes cleaning easier.
Thermostatically-controlled dehydrators can be purchased at many appliance stores, and are preferable as they use much less electricity and dry at the proper temperature, are convenient, easy, and not too expensive.  Depending on the model, you may need to rotate trays during the drying process so all vegetables are dried uniformly.  Herbs dry best with these, as they only require about 110 degrees-- too low for most ovens.  You may consider freezing herbs instead, as they will lose less flavor and oils than with drying.
Depending on your heat source and level, and water content of the crop, figure on 6 to 12 hours for drying.  Less is needed for parsley and herbs.  Twelve or more hours may be needed for broccoli, Brussels sprouts, cauliflower, chili peppers, eggplant, squash, and some tomatoes.  Drying in dehydrators goes fastest on less humid days and by not overloading the dryer.

To test for dryness, take a sample and allow to cool for a few minutes.  When warm, produce feels soft and supple.  Dried properly, it should feel crisp and brittle, although this varies some with the crop.  Peas will be hard and wrinkled, spinach and greens will be crisp, herbs will be flaky, squash and eggplant will be leathery.
Keep in mind dried produce occupies much less space in storage than fresh: 15 pounds of carrots yield just over a pound of dried product or about 2 to 4 pints, for instance.  For peas, 8 pounds fresh yield about one pint dried, for snap beans 6 pounds fresh yield about 2 and a half pounds dried.

In general, you might figure that one cup of dried vegetables will reconstitute to about 2 cups.  To cook dried, leafy or tender vegetables (such as spinach, cabbage, or tomatoes), cover with hot water and simmer until tender.  To cook root, stem and seed vegetables (such as carrots, green beans, peas and corn), first soak for 30 to 90 minutes in cool water or cover with boiling water and soak for 20 to 60 minutes.  Then, simmer these presoaked vegetables until tender.
Whether you preserve vegetables by drying or other means, it enables you to continue enjoying varieties through the fall and winter you wont find in stores, can save you money, and you don't have to worry about safety issues knowing just where your produce came from. 

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