There seems to be a bit of controversy regarding the temperature for drying
fruits and veggies. Even some books and dehydrator manuals recommend drying at
135 to 140 degrees.
However, there is something I have found that they rarely seem to mention, and
that is "case hardening"
Case hardening is caused when the temperature
is too high. It seals the surface, not allowing all moisture on the inside to
escape. That puts your food at risk for
spoilage later down the line.
"Fruits
are best dehydrated between 125°F and 135°F – any hotter than that may cause
the skins of certain fruits to get crusty i.e. 'hard' - this is known as 'case
hardening' which prevents the inside of the fruit from drying properly. Don't
be tempted to turn the food dehydrator on high to speed up the process!"
"Case
hardening is a result of partially dehydrated food that. Case hardened food has
the outermost portion of the food dried while the interior remains moist. This
situation typically results when too high of a drying temperature is used. Case
hardened foods will spoil due to microbial growth. Moisture from the interior
of the food will migrate to the exterior."