A STUDY OF THE PRIMARY PHASE OF FOOD FREEZE-DRYING IN VACUO

In the development of a novel freeze-drying technique in a fluidized bed at atmospheric pressure, a parallel study was undertaken using a conventional vacuum equipment. Two kinetically distinct phases were observed during freeze drying of representative food samples: a period during which the rate of drying was constant and a second period during which the drying rate suffered continual reduction. This paper focuses attention on the primary drying period which corresponded with the kinetics of sublimation of pure ice.