Select only ripe, unbruised fruits and vegetables and wash them thoroughly. Peel vegetables and fruits you would normally peel; slice them 1/8 to 1/4 inch thick. Quarter large tomatoes and halve plum or cherry tomatoes; dry them skin down. Dry peas, asparagus, and small mushrooms whole.
Dip sliced apples, pears, and bananas in lemon juice to preserve their color. Or drop them in a solution of 1 teaspoon ascorbic acid and 1 quart water and leave them for 2 to 3 minutes. Halve and pit apricots, plums, peaches, cherries, and nectarines; treat these also to prevent darkening.
Most fruits and vegetables should be blanched before drying to destroy enzymes that cause deterioration. Put the produce in a metal colander or wire basket set over 1 to 2 inches of boiling water. Cover and steam for the specified time; rinse in cold water. Mushrooms, onions, peppers, bananas, figs, grapes, and plums do not need blanching. Drying food in the sun In a hot, dry climate (daytime temperatures above 90F), lay blanched fruits or vegetables on trays of wooden slats or nonmetal screening and set them off the ground in a sunny spot. At least once a day, turn the foods. At night cover the trays with plastic or carry them indoors. Most foods will dry in 3 to 5 days. If rain interrupts the drying, finish it indoors. Drying food indoors A homemade or commercial dryer is best for indoor drying. An oven can be used if its temperature can be maintained between 95F and 145F; it generally works faster than a dryer. Arrange the food in a single layer on drying racks or cookie sheets; place the sheets in the oven, allowing 3 to 4 inches between racks. Leave the oven door open a crack and direct a fan toward the opening. Periodically rearrange the food to ensure even drying.
Fruit is dry when it is pliable and leathery with no moistness in the center. Most vegetables should be crisp.
To prevent spoiling during storage, pasteurize dried foods for 15 minutes in an oven set at 175F Leave dried food in covered bowls or jars for 5 to 10 days. If condensation appears, dry the food for a few more hours.
Store dried foods in airtight containers in a cool, dark place. Most vegetables will keep for 6 months, fruits for a year.