Rehydration of osmotically pre-treated apple cubes dried by hot air, microwave, and freeze-drying

Effects of the osmotic pre-treatment (OD) with sucrose or sorbitol solutions and different drying methods on the rehydration kinetics of apple cubes were studied. Samples were dried by hot air (HAD) at 70 ºC, by microwave (MWD) at 500 W, and by freeze-drying (FD). The rehydration of dried samples was performed in water at 80 ºC and at a mass ratio of sample to water of 1:100. The first order kinetic model was found to provide the best fit of the rehydration data. The pre-treatment and the drying method did not affect the rehydration kinetics, but the rehydration capacity after 12 min of rehydration was higher in the control samples than in the osmotically dehydrated ones, for all three drying methods. The rehydration rate and the rehydration capacity of the apple cubes dried by HAD, MWD, or FD were not affected by the solute used in the pre-treatment, sucrose and sorbitol.