Study on Mass Transfer and Cracking Mechanism in a Rice Grain During Moisture Absorption

The shape of the rice grain was assumed as an ellipsoid. In a cylindrical coordinate system, finite element simulations of the transient moisture distribution and stresses distribution in the rice grain during the moisture absorption were carried out. The results indicated that, during the moisture absorption, the outer portion of the grain was equilibrated rapidly, but the moisture content in the central portion increased slowly. The moisture absorption induced compressive stresses in the outer portion and tensile stresses in the inner portion of the grain. The fissuring of rice is more likely to be initiated at the center of the grain. The similar results were obtained in the experiments.