FACTORS INFLUENCING THE DRYING OF PRUNES .1. EFFECTS OF TEMPERATURE UPON THE KINETICS OF MOISTURE LOSS DURING DRYING

The kinetics of the drying of prunes (Prunus domestica) have been inve stigated as a function of temperature (70-100 degrees C). The variety of plum used was D'Agen. The prunes were dried in an oven under exhaus t conditions resulting in a constant relative humidity during drying ( 70-80%). It was found that simple first-order kinetics fitted the expe rimental data well. This is consistent with a diffusion-controlled pro cess through the fruit matrix. The activation energy plot was found to be non-linear with a much higher activation (80 kJ mol(-1)) at the lo wer temperature end. This indicates a more hindered path for diffusion of the water through the matrix. This is consistent with what is know n about the temperature dependence of cell rupture and disturbance of structure in such a material. In addition, estimates of diffusion of w ater through the food matrix are much slower than the self-diffusion c oefficient of water across the entire temperature range. This also emp hasises the hindered nature of the process. Copyright (C) 1996 Elsevie r Science Ltd