Properties of Brown Rice Kernel for Calculation of Drying Stresses
Some properties required for the calculation of the internal stresses of a rice kernel during the drying process have been measured. The mechanism of moisture movement in a rice kernel has been discussed experimentally and the average equivalentradius and the moisture diffusivity of a brown rice kernel have been determined. By examining the experimental results on volume change with moisture content of brown rice kernels, the coefficients of cubical and linear hygroscopic expansion have been estimated. The compression and stress relaxation tests were made by using test pieces of the rice endosperm formed into cylindrical shapes under various temperatures and moisture contents. Empirical equations for the compresive and shear stress relaxation moduli of rice endosperm have been obtained as a function of time, temperature and moisturecontent. Furthermore, equations for estimating the master curves on the moduli have been derived by assuming that the rice endosperm was a thermo- and hydro-rheologically simple material.
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