I don't know about large scale dehydration of general fruit/vegetable product, but the method I use for making beef jerky is one I learned from Alton Brown's "Good Eats" show and it works amazingly well:

http://www.youtube.com/watch?v=NUu9goMp7EI

(skip to around 2:15 for discussion on dehydrator technology, or skip to ~4:15 to see the method)

Basically, new (clean) air filter cartridges filled with the food. These are strapped to a box fan and the fan runs until the food is dried. Basic, cheap, and simple.

The advantage is that no heat is used, which keeps the food out of the "danger zone" where bacteria grows.