Fresh watermelon is a naturally sweet treat, but to make it even more delectable, dehydrate it. The dehydration process removes all the water and accentuates the sweet flavor of the fruit, and you can rescue a less-than-perfect or slightly overripe melon by dehydrating it. A dehydrator is the most effective way to dry watermelon, but you can also use other methods. Store the dried watermelon in clean, airtight containers.
To prepare watermelon for drying, wash the melon under cool tap water and pat it dry with a paper towel or clean cloth. Slice the melon crosswise into 1/2-inch slices; then cut the slices in half. Remove the rind from the melon, along with all traces of white. You can cut the melon pieces into wedges or strips about the size of a tortilla chip. To keep the cut melon fresh, dry it immediately or store it in the refrigerator.
The dehydrator is the preferred drying method for watermelon because the low temperature is easily maintained. To dry melon in a food dehydrator, arrange the slices on the trays in a single layer with no overlap and set the thermostat at 135 degrees Fahrenheit. Dry the fruit for 3 to 4 hours; then rotate the trays by moving each tray down one rack, and move the bottom tray to the top rack. Continue to rotate the trays every 3 to 4 hours until the fruit is uniformly dry and crisp and no longer sticky or gummy. Drying melon in the dehydrator generally takes 18 to 20 hours.
Drying watermelon in the oven is a lengthy process that usually requires 18 hours or more. This method requires considerable attention and works best for small batches. To dry it in the oven, arrange the melon in a single layer on a baking tray or cookie sheet, with no overlap. Allow about 1 1/2 inches of empty space on each side of the tray to allow air circulation around the fruit. Turn the oven on the lowest temperature and place the tray in the oven. To monitor the temperature, place an oven thermometer where it is easily visible and check the temperature every 30 minutes. You may need to prop the door slightly ajar with a block of wood or a potholder to maintain the temperature between 140 and 160 degrees F. If you still have trouble maintaining the temperature, place a small fan in front of the oven door to circulate the air. Stir the melon every half-hour and flip it occasionally to prevent sticking. The melon is sufficiently dry when it is no longer moist and sticky. After the melon cools at room temperature, it is ready to store in airtight containers.
Although it isn't impossible, drying melon in the sun is difficult, and results are varied, primarily because of the high water content of the melon, and because the source of heat -- the sun -- is less dependable than dehydrators or ovens. If humidity is low and summer temperatures are reaching triple digits, you may want to give it a try. Arrange the melon pieces on a tray; then cover the tray with netting or cheesecloth to keep the fruit clean and free of insects and birds. Place the tray in direct sunlight and turn the fruit daily. If the temperature drops more than 20 F at night, or if it rains, it's important to bring the tray inside. Drying melon in the oven generally requires a minimum of two to four days.