Mass Transfer during Osmotic dehydration of Apple using Sucrose, Fructose and Maltodextrin Solution

摘要

Osmotic dehydration is a process in which partial water is removed by immersion of water containing cellular solid in a concentrated aqueous solution of high osmotic media for a specified time and temperature. It has potential advantages of less heat damage, good blanching effect, less enzymatic browning, better retention of flavour and energy saving because no phase change occurs. Osmotic dehydration of apple was carried out using aqueous solutions of sucrose, fructose and maltodextrin of different concentrations (40, 50 and 60 %) as osmotic media, at different temperature levels (40, 50 and 60 °C) and solution to sample ratio 5:1 with agitation. The experiments were carried out upto 240 min and samples were taken for analysis at an interval of 10 min upto first 60 min, followed by intervals of 30 min for the next 180 min to evaluate moisture loss and solid gain during osmotic dehydration. Both moisture loss and solid gain increased in a non linear manner with time at all concentrations of sucrose, fructose and maltodextrin at different temperatures. It was faster in the initial period of osmotic dehydration and then the rate decreased. This study has also tried to investigate the effect of sucrose, fructose and maltodextrin solutions on mass transfer during osmotic dehydration of apple. The moisture loss and solid gain, both, were higher for the samples osmosed in fructose compared to those osmosed in maltodextrin and sucrose at the same concentration and temperature of solution. Both moisture loss and solid gain increased with increasing the osmotic agents’ concentration and temperature of osmotic solution. Drying data were fitted using Lewis, Henderson, Logarithmic and Parabolic models. Effective diffusivity values were determined at different temperature and values increased with increasing temperature of osmotic solution during osmotic dehydration.