Fissure formation in rice kernel based on glass transition theory

The fissure formation in rice kernel has been studied by many researchers, because it is the major cause to reduce the head rice yield. The reason for fissure formation based on glass transition was introduced during drying and tempering in this paper. In the course of drying, the glass state was formed in kernel appearance and inner part of kernel was still in rubbery state, and there was an interface between rubbery and glass state. Because the thermal expansion coefficient of rubbery state was many times larger than that of glass state, the tiny fissure formed in the interface between rubbery and glass state under an enough moisture gradient, and then the tiny fissure extended to a big fissure. In the course of tempering, the different parts of rubbery state in kernel can transit to glass state under different moisture gradients, the tiny fissure formed in the part of glass state. Based on the above analysis, two methods to prevent the fissure formation can be obtained. One method is changing temperature drying, the rice kernel must still be in glass state during drying. The other method is high temperature drying, the rice kernel must still be in rubbery state.