MASS TRANSFER KINETICS DURING OSMOTIC DEHYDRATION OF AONLA SLICES (Emblica officinalis Gaertn.) OF Cv. NA-7 PRIOR TO AIR DRYING

Osmotic dehydration of aonla slices of NA-7 variety was carried out in order to remove partial moisture prior to mechanical drying by employing sugar syrup solution (50, 60 and 70oBrix) at sugar syrup temperatures (40, 50 and 60?C) and immersion time (15, 30, 60, 90, 120, 180 and 240 min) maintaining constant solution to fruit ratio of 6:1 (v/w). The effects of syrup concentration, syrup temperature and immersion time on water loss and sugar gain were observed. It was found that water loss and sugar gain both were increased non-linearly with syrup concentration, temperature and immersion time and found in the range of 13.60 to 59.52 and 2.53 to 17.10 %, respectively. Among the seven existing mathematical models tried, the logarithmic model was found adequate to describe the water loss for all the temperature-concentration combinations except treatment of 60?C-70?B for which power model was found adequate based on regression diagnostic criteria. For sugar gain, the quadratic model for 40?C-50 ?B, cubic model for 40?C-50 and 70?B, 50?C-50 and 70?B and for 60?C-50?B noticed best fit however, the logarithmic model was found best for 50?C-60?B, 60?C-50 and 60?B temperature-concentration combinations. The developed models can be used for predicting water loss and sugar gain during osmotic dehydration of aonla slices within the range of experimental study.