At once tart, sweet, juicy and crisp, a perfectly ripened fresh apple is a satisfying snack. Apples also keep well, lasting for weeks at room temperature and a month or two in the fridge. Drying apples extends their usable life to months or even years, with the added benefit of substantially reducing their weight and volume. You can easily dry your own at home, even if you don't own a dehydrator.
Both firm and mealy apple varieties can be dried, though firmer apples make neater slices. Choose perfect, unblemished specimens and slice them as evenly as possible, so they'll dry consistently. A mandoline slicer, or the rotary cut-core-peel gizmos sold at most kitchenware stores, provides perfectly even slices and also speeds your preparation. Apples brown and soften quickly once they're cut, so dip them in an anti-browning solution of water with ascorbic or citric acid or -- if you don't keep those on hand -- equal parts water and lemon juice. This inhibits bacterial growth, aside from its aesthetic value.
Countertop dehydrators offer the most efficient drying method. Arrange your apple rings or half-moon slices on the trays, ensuring they don't touch and leaving plenty of room for air to circulate. If your model has variable temperatures, 125 to 135 degrees Fahrenheit is ideal. Single-temperature models are slightly warmer, at 140 F. Dry the apples until they're leathery and no longer tacky, which can take as little as 4 hours or as long as 10 to 12, depending on the thickness of your slices. If your goal is crisp apple "chips," leave them in the dehydrator until they're hard and brittle. In some models, you might need to periodically shuffle the trays to ensure even drying.
If you don't own a commercial food dehydrator, your oven will also do the job. Arrange the apples on a parchment-lined baking sheet, or -- better yet -- a wire rack resting on a baking sheet. Turn your oven to 140 F, or whatever is its lowest possible setting. Prop the door open, if necessary, to keep the temperature low. Oven-drying can take 10 to 20 hours, because unlike a dehydrator, most ovens lack a fan to push the air around. Use your oven's convection fan, if applicable, or set a fan at the door's opening to push air through, to speed the process. Turn the slices periodically to ensure even drying.
Fruit always dries unevenly, thanks to the vagaries of air flow, so your dehydrated apples will keep more reliably if you "condition" them after they've dried. That simply means bundling the slices into sealed jars for a week or so, which provides opportunity for the moisture inside to equalize. If you see condensation inside the jar, your apples weren't dried enough and need more time. Once conditioned, freeze the slices for 48 hours to kill any insects or eggs that might be present. Package the dried slices in airtight bags or sealed containers, and store them in a cool, dry place for up to a year.