HOME dehydrators cost anywhere from $99 to $300, says Pat Worthington, a Newington, Va., cooking instructor and special guest lecturer at the Cooperative Extension Service workshop.

A good one for home use should cost between $125 to $150 and should have regulated temperature control and good airflow, she says. In addition, the typical home gardener will want at least 10 trays for dehydrating so that one-third to one-half bushel of produce can be processed at one time.

A standard oven held at a constant temperature of 150 degrees can also be used to dry foods, according to the Cooperative Extension Service. The only thing you must do is allow moist air to escape either through a vent or by leaving the oven door slightly ajar. To keep oven moisture and drying time to a minimum, dry only four to six pounds of produce per batch.

Whether you dry produce in a dehydrator or oven, be sure to follow these tips:

* Select fresh, ripe foods. Immature foods lack flavor and color. Overly mature foods may be tough or mushy.

* If using a dehydrator, remove trays and turn on the unit. Many dehydrators have built-in temperature regulators to keep the heat at around 140 to 150 degrees; if yours does not, then you'll want to monitor the heat. Temperatures over 150 degrees will burn food on the outside, leaving the inside moist; anything under 120 degrees will dry too slowly. Either problem can cause food spoilage.

* Treat trays with a non-stick cooking spray to prevent produce from sticking. Pam or lecithin (a soybean emulsifier) work well, Worthington says. You can also use a flexible mesh insert. "Lots of things stick to trays if you don't use spray. For example, for something like tomatoes or zucchini you're going to have a dickens of a time getting them off" after they have dried, Worthington said.

* Slice vegetables or peeled fruit in uniform pieces. (Peels can be left on apples, but they tend to taste bitter after drying.) Trim away inedible or damaged portions.

* Blanch vegetables or treat fruit with an antioxidant coating to stop enzyme activity (which leads to discoloration and flavor changes) and to seal in vitamins and set the color. Blanching times vary: After you have added the produce and water returns to a boil, blanch leafy vegetables 1 to 3 minutes; peas, beans and corn 2 to 8 minutes; potatoes, carrots and similar vegetables 3 to 6 minutes. Use commercial antioxident coatings such as Fruit Fresh or ACM or use plain lemon juice, orange juice, ascorbic acid or vinegar and water to stop the darkening of fruits.

* Place produce on dehydrator tray (or cookie sheet for oven drying) in a single layer, arranging pieces so they touch but do not overlap.

* The dehydration time also varies, depending on how juicy the produce is and how much food is being dehydrated (more food takes a longer time). Apples, for example, generally take six to 10 hours. Try not to mix produce of varying moisture content--for instance, don't dry zucchini (98 percent moisture) with a food like bananas (76 percent moisture), Worthington says. Drying times also vary according to how long you plan to store the food. For long-term storage, the produce should be brittle; for short-term storage, it should be pliable or hard. "It's all very subjective," Worthington says. "If you're going to eat an apple as a snack, you'll want it leathery; if you want to put it away for winter, you'll want it really crisp." To test for dryness, remove a handful, allow to cool slightly (warm food always feels more moist) and judge by feel.

* To store: let cool completely (since heat retains some moisture). This usually takes about one hour. Place in moisture-free jars with tight-fitting lids and fill to maximum capacity to evacuate as much air as possible (which carries excess moisture). Store in a cool, dry, dark place.

* Rehydration time varies. Root, stem and seed vegetables should be covered with cold water for one-half to two hours, then simmered just until tender, allowing excess water to evaporate. Extension agents advise using the food in soups, casseroles, stuffings and the like. To rehydrate fruit, simply cover with water (hot water will hasten the process) and soak one to eight hours or until they reach a desirable consistency. PINEAPPLE-POPPY SEED CAKE 1/2 cup powdered dried pineapple 1/2 cup poppy seeds 1 cup milk 1/2 cup shortening 2/3 cup sugar 1/2 teaspoon vanilla 2 cups flour 2 teaspoons baking powder 1/4 teaspoon salt 2 eggs, beaten Caramel topping: 1/4 cup butter 1 cup packed brown sugar 1 tablespoon flour 1/2 cup water 1 teaspoon powdered dried orange peel 1 egg, beaten 1/2 pint whipping cream 1 tablespoon sugar 1/2 teaspoon vanilla Pulverized dried pineapple

Soak powdered dried pineapple and poppy seeds in milk for 15 minutes. Cream together shortening, sugar and vanilla. In a separate bowl mix flour, baking powder and salt. Combine half the dry ingredients with the creamed mixture. Add rehydrated pineapple and poppy seeds and the remaining dry ingredients. Mix well. Blend in beaten eggs. Pour into a greased and floured 9-by-13 inch pan. Bake at 350 degrees for 35 minutes or until done. Cool.

To make topping combine butter, brown sugar, flour and water in a saucepan. Add dried orange peel and beaten egg. Mix thoroughly. Cook over medium heat, stirring constantly, until mixture begins to thicken. Remove from heat and cool. Caramel will continue to thicken as it cools. Meanwhile, whip cream, adding the sugar and vanilla. Spread cooled caramel on cake, followed by whipped cream. Top with pulverized dried pineapple. Keep refrigerated.

From "Dehydration Made Simple," by Mary Bell.