Using a food dehydrator is one of those kitchen activities that's part cooking, part science project. With a gentle blast of warm air, you can turn slices of fresh fruits and vegetables into crispy, crunchy, vitamin-packed snacks. The process is simple: a heating element acts as a low-temperature oven, while a fan circulates the warm air for maximum evaporation of moisture from foods. All you have to do is place the food on the dehydrator trays, set the temperature and timer, then check for doneness. There's plenty of room for experimentation, such as seasoning sweet potato chips with rosemary or sprinkling fruit slices with cinnamon, as you'll see in the easy recipes that follow. 4 Easy Steps1. Arrange seasoned or plain sliced fruits and vegetables on dehydrator trays without overlapping. 2. Set the temperature. For foods to dry out completely and still be considered raw, the temperature should be set to 104°F. Cooks who aren't concerned with the raw aspect may prefer setting the dehydrator to 135°F to shorten drying times. 3. Check regularly, and rotate trays. Dehydrating fruits and vegetables can take 2 to 19 hours, depending on moisture content and humidity in the air. To test for doneness, cut a slice. Food is dehydrated when no moisture beads appear in the cut. 4. Cool and store in an airtight container in a dark, dry place. If leftovers lose their crispness, return to dehydrator 1 to 2 hours to restore the desired texture. Which Dehydrator is Right for You? Dehydrators vary widely in price (from $10 for a used item on eBay to $300 for a semiprofessional model) and in practicality. Here's a rundown on three popular models. NESCO FD-80 SNACKMASTER SQUARE DEHYDRATOR & JERKY MAKER$99.95; nesco.comFeatures: Adjustable thermostat, top-mounted fan, and 700 watts of drying power. Comes with four trays (shown), expandable to eight. Best for: Cooks who do occasional dehydrating in small batches. NESCO FD-1020 GARDENMASTER DIGITAL PRO FOOD DEHYDRATOR$169.99; nesco.comFeatures: 1,000 watts, plus a digital thermostat and timer take the guesswork out of dehydrating. Can be used with a few trays or expanded to accommodate 20 trays. Best for: Food lovers who want plenty of options. EXCALIBUR 9-TRAY LARGE DEHYDRATOR WITH 26 HOUR TIMER$299.95; excaliburdehydrator.comFeatures: Fan at the back of the element evenly circulates air to all trays. Tray setup can be changed to leave more space and allow more air to flow over foods. Best for: Seasoned raw foodists who prepare large batches of dehydrated fruits and vegetables.