KINETICS OF OSMOTIC DEHYDRATION OF A HIGHLY SHRINKING VEGETABLE TISSUE IN A SALT-FREE MEDIUM

The kinetics of water removal and solute uptake during osmotic dehydra tion of a highly shrinking vegetable tissue (potato) in a salt-free os motic medium (corn syrup solids) were studied. Increased temperatures (up to 45 degrees C) gave highly increased rates of dehydration and ne t loss of soluble solids ranging between 4.4 and 13.4% of total initia l solids. Half dehydration time at 50 degrees C, was half of that meas ured at room temperature. Processing at 50 degrees C, however was foll owed by extensive, nearly linear (with time) sugar uptake, reaching 50 % of initial solids within 5 h. Half dehydration time and mass (water) diffusivity followed Arrhenius type kinetics with activation energies of 21.2 and 28.7 kJ mole(-1) respectively. Shrinkage experiments reve aled a very strong correlation between the rate of volume decrease and the rate of moisture removal. Within the industrially applicable proc essing time, volume of removed water was identical to shrinkage induce d loss of product volume. Concentrated solutions of corn syrup solids seem to be suitable for efficient osmotic dehydration of potato-like v egetable tissues, without suffering the negative impact of extensive s olute uptake. Copyright (C) 1996 Elsevier Science Limited