Modelling the hydration of foodstuffs

The rehydration kinetics of dried foodstuffs is of critical importance to their sensory properties and delivery of flavour and functional molecules. Based on the dynamics of capillary flow in partially saturated porous media, a finite element model is developed to predict the infiltration of water into dried food products taking into account temperature effects. The finite element model is based on the mixed form of the mass conservation equation. The constitutive relationships of water retention and hydraulic conductivity are adopted from the fields of hydrology and soil science. The transfer properties of water in the porous medium depend on the moisture content and the microstructure. This is contrast to the constant transfer properties often used in the heat and mass transfer models developed for foods. Rehydration of green tea as a function of temperature has been simulated and results are compared with NMR measurements. There is good agreement.