To remove the natural moisture from food by slowly drying it. Considered the original form of food preservation, dehydration prevents moisture spoilage such as mold or fermentation. Food can be dehydrated manually by placing thin slices on racks and allowing them to dry assisted only by sun or air. It can also be done with an electric dehydrator, which resembles a large three-sided toaster oven with anywhere from 5 to 10 wire-grid racks. The food placed on these racks dries with the aid of fan-circulated air. Dried foods are convenient to store and transport because of their greatly reduced volume and weight.