The role of heat and mass transfer phenomena in atmospheric freeze-drying of foods in a fluidised bed

Freeze-drying under atmospheric pressure in a fluidised bed of adsorbent fine particles is proposed for dehydrating food products at lower cost than the traditional freeze-drying process under vacuum. The aim of this paper is to evaluate the role of heat and mass transfer coefficients between the product and the bed during the process at atmospheric pressure and to analyse the effect of transport coefficients and operating variables on freeze-drying rates. Experiments were performed using potato cylinders as the test material. The results obtained are discussed also in connection with further developments of this technique and optimal design of the process. (C) 2003 Elsevier Science Ltd. All rights reserved.