Stochastic approach to the modelling of water losses during osmotic dehydration and improved parameter estimation

The kinetics of water loss in the apple cultivar Golden during osmotic dehy dration in sucrose solutions was studied. Two sets of experiments were perf ormed, each following a full factorial design at five levels for sucrose co ncentration (0.45-0.65 w/w) and temperature (20-40 degreesC). The first set was designed to assess the adequacy of the Weibull model to describe water losses, whereas the second set was designed to improve parameter estimatio n, based on the D-optimal design concept. The model provided good fits to t he experimental data, and the D-optimal design yielded improved parameter p recision. The shape parameter of the model was 0.5 and statistically indepe ndent of both temperature and sucrose concentration. The rate constant rang ed between 0.004 and 0.012 min(-1) and increased with temperature following an Arrhenius type relationship, with the activation energy increasing line arly with concentration. The interactive effects of temperature and sucrose concentration on the process kinetics were analysed.