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 dehydration of a highly shrinking vegetable tissue (potato) in a salt-free osmotic medium (corn syrup solids) were studied. Increased temperatures (up to 45 degrees C) gave highly increased rates of dehydration and net loss of soluble solids ranging between 4.4 and 13.4% of total initial solids. Half dehydration time at 50 degrees C, was half of that measured at room temperature. Processing at 50 degrees C, however was followed 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 revealed a very strong correlation between the rate of volume decrease and the rate of moisture removal. Within the industrially applicable processing time, volume of removed water was identical to shrinkage induced loss of product volume. Concentrated solutions of corn syrup solids seem to be suitable for efficient osmotic dehydration of potato-like vegetable tissues, without suffering the negative impact of extensive solute uptake. Copyright (C) 1996 Elsevier Science Limited