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 dehydration in sucrose solutions was studied. Two sets of experiments were performed, each following a full factorial design at five levels for sucrose concentration (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 estimation, based on the D-optimal design concept. The model provided good fits to the experimental data, and the D-optimal design yielded improved parameter precision. The shape parameter of the model was 0.5 and statistically independent of both temperature and sucrose concentration. The rate constant ranged between 0.004 and 0.012 min(-1) and increased with temperature following an Arrhenius type relationship, with the activation energy increasing linearly with concentration. The interactive effects of temperature and sucrose concentration on the process kinetics were analysed.