Mass exchange during osmotic pretreatment of vegetables

Apple, pumpkin and carrot were used to study mass transfer during osmotic dehydration of plant tissue. Osmotic dehydration was carried out in 61.5% solution of sugar. Temperature of dewatering was constant at 30 degreesC. Time of dehydration was varied from 0 to 180 min. Osmotic dehydration in sugar solution at 30 degreesC depends on the kind of plant tissue. The most significant changes of water content, water loss and solids gain took place during the first 30 min of dewatering. During that time water content in apples was reduced by some 48%, whereas further dehydration from 60 to 180 min resulted in water content reduction by next 30%. Further dewatering of pumpkin and carrot proceeded much slower than that at the beginning of the process. Rate of water loss was 5-10 times higher than the rate of solids gain and depended on the advancement of the dewatering process. (C) 2001 Elsevier Science Ltd. All rights reserved.