Michigan State University Extension
Preserving Food Safely - 01600518
1. Trays must be at least 1 1/2 inches narrower than the inside of the oven to allow for air circulation. Allow at least 2 1/2 inches between trays and 3 inches of free space at the top of the oven. Cheesecloth may be spread over the trays (under the food) to prevent small pieces from falling between the slats.
2. Load two to four trays with no more than 4 to 6 pounds of prepared vegetables distributed among them. Vegetable pieces should be in a single layer. More than one kind of vegetable can be dried at the same time. Strong-smelling vegetables should be dried separately.
3. Place an accurate and easily read thermometer on the top tray toward the back.
4. Preheat the oven to 160 degrees Fahrenheit (71 degrees Celsius), and then add the loaded trays. Prop the door open at least 4 inches.
5. Place a fan outside the oven in such a position that air is directed through the opening and across the oven. Change the position of the fan frequently during drying to vary the circulation of the air.
6. Maintain the temperature at 140 degrees Fahrenheit (60 degrees Celsius). It takes less heat to keep the temperature at 140 degrees Fahrenheit as drying progresses, so watch the temperature carefully toward the end of the drying.
7. Examine the vegetables often, and turn the trays frequently. At the start of the drying process, there is little danger of scorching, but when nearly dry, the product may scorch easily. Even slight scorching destroys the flavor and may lower the nutritive value, so be careful not to allow the temperature to rise above 140 degrees Fahrenheit, especially during the latter stage of drying.
NOTE: Tests for dryness will come with experience. The approximate drying times are merely a guide to judging proper dryness. Most vegetables will be brittle when dry and would shatter if hit with a hammer.