Prediction of Transient Temperature Distribution During Freeze Drying of Yoghurt

A one dimensional heat and mass transfer analysis is employed to predict the temperature distribution in the dry layer of a frozen food sample in the form of a slab undergoing freeze drying. The method avoids the use of the effective diffusivity and the Knudsen diffusivity, both parameters dependent upon the stnrcture of the food product. The accu acy of the numerical solution is validated with published data as well as data of present study obtained for the freeze drying of yoghurt. The predicted surface temperature of the food sample is in good agreement with the experimental data. Energy supplied to product surface through conduction across evacuated head space was found to be significant. The model is useful for the analysis of freeze drying of a food product.