Dried apples are a tasty, portable and healthy snack. Keep in mind that the more flavorful the fresh apples you start out with are, the more delicious the dehydrated version will be.
Peel core the apples
Use a vegetable peeler to remove the apple peels. Although it's totally possible to skip this step if you're pressed for time, the peels will be sharp-edged and tough when dried.
Cut out the cores.
Slice the apples
Cut the apples into slices that are approximately 1/4-inch thick.
As you slice the apples, drop the pieces into acidulated water to prevent them from browning. You can make acidulated water by adding 1 1/2 tablespoons of vinegar or lemon juice to a quart of water. Leave the slices soaking in the acidulated water while you finish slicing the rest of your apples.
Drain the apples
Once all of the apples are sliced and have had a soak in the acidulated water, drain them in a colander. Let them sit in the colander for 2 to 3 minutes to drain off as much water as possible.
Arrange the apple slices for drying
Place racks inside baking sheets and arrange the apples on the racks so that none of the slices are touching.
Dry the apples
Turn the oven on to its lowest setting, which is usually between 140F - 150F. Prop the door of the oven open with the handle of a wooden spoon (this isn't necessary if you are using a convection oven).
Put the apple-loaded baking sheets in the oven. Let the apples dry until they are leathery to crisp, which can take anywhere from 6 to 10 hours. If your oven is hotter in some spots than others, turn the baking sheets around occasionally so that the pears dry evenly.
Cool the dried fruit
You won't be completely sure if the apple pieces are fully dehydrated until they have cooled (you know how cookies crisp up after you take them out of the oven? Same deal with dried fruit). Remove the trays from the oven. Let the apples cool on the trays for 20 minutes.
After the cooling off period, tear one of the pieces of fruit in half. There should be no visible moisture along the surface of the break.
Condition the dried apples
Even after the apples are correctly dehydrated there may still be some residual moisture in the fruit that you can't feel. This shouldn't be enough to prevent the fruit from being safely preserved and mold-free. But you'll have a tastier, better product if you do what is called "conditioning" the dried fruit.
Put the dried, cooled apple slices into glass jars, only filling the jars about 2/3 full. Cover the jars. Shake the jars a couple of times a day for one week. This redistributes the fruit pieces as well as any moisture they may still contain. If any condensation shows up on the sides of the jars, your fruit isn't dried well enough yet and it needs to go back into the oven on its lowest setting for an hour or two.
Once your dried apples are conditioned, store them in airtight containers away from direct light or heat. It's okay to fully fill the jars at this point: the 2/3 full was just for the conditioning phase when you needed to be able to shake the pieces around.