Kinetics of solute gain and water loss during osmotic dehydration of orange slices

The effect of the osmotic solution (sucrose and dextrose syrups) on the kinetics and process yield was evaluated on osmotic dehydration of orange (Valencia Late var.). Processes were carried out at 30degreesC, using 35, 45, 55 and 65degreesBrix solutions and by applying a vacuum pulse (100 mbar for 10 min) at the beginning of the process. Kinetics of sugar gain-water loss and mass changes were analysed by separately considering peel and pulp fractions of orange slices. Mass transport properties of orange slices in osmotic treatments were different for pulp and peel fractions due to the different contributions of the mechanisms involved. Faster water and solute transport were observed in the peel impregnated with the osmotic solution. Sugar gain in sucrose solutions was enhanced in comparison with dextrose treatments, whereas diffusional water loss was faster in samples treated with dextrose. These effects made the process yield higher for sucrose treatments. An increase in the osmotic solution concentration implied higher mass transport rates, but did not notably affect process yield.