Drying fruit and vegetables at home is straightforward in principle and frequently disappointing in practice. The most common reason is not the dehydrator, the temperature or the timing. It is that the slices were not the same thickness.
The Physics of the Problem
Drying removes moisture from the surface inward, and the time required depends on how far the moisture has to travel. A slice twice as thick takes considerably more than twice as long.
Put slices of varying thickness on the same tray and there is no correct finishing time. Remove them when the thin ones are done and the thick ones retain moisture, which means they will spoil in storage. Leave them until the thick ones are ready and the thin ones are burnt and brittle.
This is why every dehydrating guide emphasises uniform cutting, and why a slicer with a fixed adjustable thickness is genuinely the right tool. Ranges with a continuously variable bed, of the kind listed at benriner, allow one setting to be established and reproduced across an entire batch.
Target Thicknesses
- Apple and pear rings: around three to five millimetres
- Banana: three millimetres for chewy, thinner for crisps
- Root vegetable crisps: one to two millimetres
- Tomato: around five millimetres, since they lose enormous volume
- Courgette and cucumber: two to three millimetres
Preparation Beyond Slicing
Apples, pears and bananas oxidise and brown. A brief dip in acidulated water, roughly a tablespoon of lemon juice per cup of water, prevents most of it without affecting flavour noticeably.
Arrange slices in a single layer without overlapping, since contact points stay moist and are where spoilage begins. Rotating trays partway through evens out drying on stackable dehydrators.
Knowing When It Is Done
Properly dried fruit is leathery and pliable with no visible moisture when a piece is torn open. Vegetables intended as crisps should be genuinely brittle.
Test a cooled piece rather than a warm one, since anything warm feels softer than it is. This catches out a great many people and results in batches that appear dry and then spoil in the jar.
Conditioning
The step most people skip. Pack the cooled pieces loosely in a jar, seal it and shake daily for around a week. Any residual moisture redistributes between pieces, and condensation on the glass indicates the batch needs further drying.
Skipping this is the usual reason home-dried fruit develops mould weeks later despite appearing dry on the day.
Storage
Airtight containers away from light give several months; vacuum sealing gives longer. Any sign of mould means the batch should be discarded rather than salvaged, since drying does not sterilise and mould in dried food can be present beyond the visible patch.
Labelling with the date matters, because dried fruit all looks similar after two months and there is no way to judge age by appearance.