A temperature of 135° to 140° F is desirable for dehydrator and oven
drying. Moisture must be removed from the food as fast as possible at a
temperature that does not seriously affect the food's flavor, texture,
color, and nutritive value.
If the initial temperature is too low or air circulation insufficient,
the food may undergo undesirable microbiological changes before it dries
adequately.
If the temperature is too high and the humidity too low, as when drying
small loads in the oven, the food surface may harden. This makes it
difficult for moisture to escape during drying.
Oven or dehydrator drying should continue without interruption to
prevent microbial growth.
To promote even drying, rotate trays occasionally and stir food if
necessary.
Drying time varies according to fruit or vegetable type, size of pieces,
and tray load. Dehydrator drying generally takes less time than oven
drying. Sun drying takes considerably more time.
Before testing foods for desired dryness, remove a handful and cool for
a few moments. Foods that are warm or hot seem softer, more moist, and
more pliable than they will when cooled.
Foods should be dry enough to prevent microbial growth and subsequent
spoilage. Dried vegetables should be hard and brittle. Dried fruits
should be leathery and pliable. For long term storage, home dried fruits
will need to be drier than commercially dried fruits sold in grocery
stores.