Food dehydrators—either commercially made or homemade—give a good quality dried product. Oven drying works well if you can set your oven to a temperature of 140 to 150°F. Open the oven door 2 to 3 inches to allow moisture to escape. A convection oven works well because it combines low heat with a fan to move the air. Room drying at room temperature works only if heat, humidity, and air movement are adequate. Today’s air-conditioned homes may be too cool to dry foods quickly enough. While sun drying works in dry climates, the high humidity in Pennsylvania makes this method impractical here.
Most foods can be dried indoors using modern food dehydrators, counter-top convection ovens or conventional ovens. Microwave ovens are recommended only for drying herbs, because there is no way to create enough air flow to dry denser foods.
The method was still used until world war two in which machines for freeze drying foods were created. Currently, all foods can be preserved using this technique. But it was coffee that was first preserved using this method. The need for freeze-dried food has been increasing, especially for space travel. This technique was still used until the Apollo missions. Along with the development of technology, food preservation becomes more efficient. NASA found a new way to preserve ice cream through freeze-drying.
A food dehydrator is a small electrical appliance for drying foods indoors. A food dehydrator has an electric element for heat and a fan and vents for air circulation. Dehydrators are efficiently designed to dry foods quickly at 140 °F. Food dehydrators are available from department stores, mail-order catalogs, natural food stores, and seed or garden supply catalogs. Costs vary from $50 to $350 or above depending on features. Some models are expandable and additional trays can be purchased later. Twelve square feet of drying space dries about a half-bushel of produce. The major disadvantage of a dehydrator is its limited capacity.