The best way I know to check if the food is completely dry is to have one larger slice of food on each tray. When the freeze dryer says ‘process complete’, open the door, and break in half the larger/thicker slice of food on each tray. If that slice is dry and there is no ice in the core, then most likely the rest of the smaller/thinner slices will be dry as well.

For liquids, check in the center of the tray for dryness.