Seven to nine hours at 57 C for 5 mm slices. Thicker slices, a full machine or a humid kitchen push that toward twelve.
The number, then the caveats
Published drying guidance puts apple slices at 7 to 9 hours at 57 C or 135 F, cut about 5 mm thick, on a machine with a rear fan. On a stacking machine with a base fan the same batch often runs 10 to 12 hours, and the bottom trays finish first.
Treat the clock as a rough guide and the texture as the real test. A finished slice is leathery, bends without snapping, and has no cool damp spot in the middle when you tear one open.
What actually changes the time
Thickness is the biggest lever. Doubling the slice thickness roughly doubles the drying time, because water has twice the distance to travel out.
How full the machine is comes next. Four loaded trays put much more water into the air than one, and the fan has to carry all of it out.
Kitchen humidity matters more than people expect. The same batch can take two hours longer on a wet day than a dry one.
Keeping them pale
Apples brown because enzymes react with oxygen once the flesh is cut. Five minutes in cold water with the juice of a lemon slows that down enough for a home batch, and it costs nothing.
Ascorbic acid, sold as fruit fresh, works better than lemon if you are drying several kilos and want them uniformly light.
Crisp or chewy
For chewy rings, pull them at leathery and condition them for a week. For crisp chips, leave them another hour or two until they snap, and get them into a sealed jar the same day.
Crisp slices pick moisture back up quickly in a humid room, which is why they soften in an open bowl within a day.
| Thickness | Temperature | Typical time | Result |
|---|---|---|---|
| 3 mm | 57 C / 135 F | 5 to 7 h | Crisp chips |
| 5 mm | 57 C / 135 F | 7 to 9 h | Leathery rings |
| 8 mm | 57 C / 135 F | 11 to 14 h | Chewy, best conditioned |
| 5 mm, full machine | 57 C / 135 F | 9 to 12 h | Rotate trays if base fan |
Safety note. Dried fruit is a quality question rather than a safety one, but it must be dry and sealed before storage. Condition the batch for a week and discard anything that shows condensation or mould.
What this is based on
- National Center for Home Food Preservation, drying fruits
- USDA guidance on home drying and storage
- University extension publications on apple drying times