Prediction of Moisture Diffusivity in Granular Materials, with Special Applications to Foods

The effective diffusion coefficient of two granular starch materials was determined from drying experiments by using the method of slopes. A method was developed, which permits the combination of the diffusion coefficient of the solid phase and the binary diffusion coefficient of water vapor in air for the prediction of the effective moisture diffusivity of the system. Several structural models of the literature were used to predict the effective moisture diffusivity of the two granular starches in the ranges of moisture content 0.0‐0.6 kg of water/kg of dry solids, porosity 0.0‐0.6, and temperature 20–100 °C. The results showed that the structural models can be successfully used for the prediction of the effective moisture diffusivity, and especially the Behrens model showed considerable merit. The diffusion coefficient of the solid phase (granule) was estimated by fitting the theoretical model to the experimental data.