An application of glass transition temperature to explain rice kernel fissure occurrence during the drying process

Fissure formation during rice drying is a major cause of rice milling quali ty reduction. This work has applied principles of polymer science in studyi ng thermal and hygroscopic properties of rice kernels, particularly the gla ss transition temperature (T-g). This data was used to develop a hypothesis that explains the occurrence of rice kernel fissuring as a result of dryin g. The drying process was mapped onto a state diagram to illustrate the cha nges in state that a kernel could incur through drying and tempering operat ions. An experiment was designed to validate the hypothesis in which the ef fect of the T-g on rice drying and tempering in terms of milling quality wa s determined. Results showed that drying air temperatures up to 60 degreesC and high moisture removal rates could be used without reducing the milling quality, as long as sufficient tempering was allowed at a temperature abov e the T-g of the rice.