The effect of pretreatment, osmotic–ultrasonic dehydration, on the rehydration kinetic of quince at three temperatures (25, 45 and 70C) was examined. The values of the effective moisture diffusivity of quinces were in the range 8.114 × 10−11 to 2.020 × 10−10 for untreated samples and 6.085 × 10−11 to 1.308 × 10−10 for pretreated samples, respectively. The temperature dependence of the diffusivity coefficient was also described by the Arrhenius-type relationship. The activation energy was found to be 14.48 and 17.27 kJ/mol, for pretreated and untreated samples quince, respectively. Five different models, Fick's second law of diffusion, Peleg, Weibull, first-order and exponential association, were evaluated based on coefficient of determination (R2), reduced chi-square (χ2) and root means error (RMSE). The Weibull model gives the highest values of R2 and the lowest values of χ2, SSE and RMSE for untreated and pretreated quince samples.
Rehydration is a complex process aimed at the restoration of raw-material properties when dried material comes in contact with water and can be considered as a measure of the injury to the material caused by drying. The capacity of the dry material to be rehydrated depends on certain intrinsic properties of the vegetal tissue and also on how the rehydration process is carried out (process conditions) and on the previous pretreatments applied to the product. These pretreatments are usually used to obtain a better quality of the final product (i.e., better preserved from undesirable changes) and in this sense applying an osmotic–ultrasonic dehydration step prior to the rehydration process could be interesting. The objective of rehydration study is to attain as many products in their original characteristics as fast as possible. An improved knowledge of rehydration kinetics would significantly enhance the feasibility of this process.