Determine Major Aspects of the Mechanism of Freeze Drying?
The major aspects of the mechanism of freeze drying are:
(a) The removal of vapour from the subliming ice front within the material,
(b) The removal of vapour from between the food particles,
(c) The supply of heat to the food particles,
(d) The supply of heat to the ice within the food particles
The conventional freeze drying unit consists of a vacuum chamber into which trays of the material to be dried can be placed, and a source for supplying heat to the material so that the sublimation process can be accelerated. The usual method is to arrange the trays on or between the heated plates, which are either electrically heated or internally heated with steam. The vacuum is produced either with a mechanical pump, suitable steam ejectors, or refrigerated condensers.