In this study, water absorption characteristics of some rice varieties (Bisalayi, FARO 61, FARO 60, FARO 52 and FARO 44) from Nigeria were studied at 30°C, 45°C, 60°C and 75°C by determining the increase in grain weight as a function of time during soaking. Differences in moisture content among the selected varieties of paddy during soaking were significant (P < 0.05) at all temperatures considered. Using the experimental moisture data, a non-linear regression procedure was applied to an analytical solution of the Fick’s second law of the diffusion for an infinite cylinder. The predicted values of instantaneous moisture contents were in good agreement with the experiential data with R2 of (0.834 - 0.997). Water absorption rate was found to increase with soaking temperature, while water saturation time decreased with temperature. Average values of diffusion coefficients of moisture during soaking of paddy rice at different temperatures (30°C, 45°C, 60°C and 75°C) were estimated as 6.25 × 10 -11, 6.28 × 10 -11, 7.02 × 10 -11, and 5.51 × 10 -11 and 5.52 × 10 -11 m2/s for Bisalayi, FARO 61, FARO 60, FARO 52 and FARO 44, respectively. The activation energies of the diffusivity through different varieties of rice grains werecalculated using Arrhenius-type equation for diffusion dependence on temperature and were determined as 41.96, 38.69, 40.16, 34.05 and 42.12 kJ/mole for Bisalayi, FARO 61, FARO 60, FARO 52 and FARO 44 for the respectively rice variety above.
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