Modeling rehydration of porous food materials: II. the dual porosity approach

Following the foundation for physical modeling of rehydration (Troygot et al.; 2011), the Richards equation together with the independently evaluated characteristic curve yielded a close approximation for the early stage (1000 s) of rehydration data. It was revealed that the porosity of wheat groats (WG) and freeze-dried carrots consists of inter- and intra-particles porosities playing a distinct role on the rehydration kinetics. A dual porosity mobile-immobile model was suggested for modeling water flow by capillarity in the inter porosity and by water-content difference (diffusion-type) in the intra porosity. The model fits the overall rehydration process well. A double Weibull distribution model predicted also well the experimental rehydration data for freeze-dried carrots verified the above, demonstrating the roles for both diffusion and relaxation in a dual-porosity structure. The physically-based model combined with the characteristic curve, hydraulic conductivity function, and a transfer coefficient for rate-limited exchange between inter- and intra-particles porosities was adequate for modeling the rehydration process of porous food.