Study On Simulation And Control Mechanism Of Rice Drying Quality

Rice drying quality was evaluated through many index. For example, rice crack ratio, seed germination, head rice yield, taste score. The cracking mechanism, the parameters of rice drying and the safe drying temperature of rice seed had been studied in this thesis based on glass transition of rice. In addition, the stochastic model of rice drying and degradation kinetic model of head rice yield had been researched. The details are as follows: 1) The methods available for measurement of glass transition temperature of rice were discussed. The glass transition kmperature of rice (Jindao 305) was determined using the Differential Scanning Calorimetry (DSC) in the experiments, and the glass transition temperature model of rice was obtained. 2) The formation of glass state within rice kernel was simulated and studied using Finite Element Method. The rice cracking was surveyed in drying experiment and craze in rice kernel was observed using microscope. The cracking mechanism of rice was studied based on glass transition. The reason of cracking formation in rice drying, cooling and tempering was analyzed. Some suggestions for decreasing rice cracking were presented. 3) The intermittent drying parameters, such as heated air temperature, limit time of heating, tempering temperature and tempering time, were studied. The model of limit time of heating and tempering time were obtained, and were validated by data of head rice yield. 4) The model of safe drying temperature of rice seed was developed based on kinetic models of germination. The germination experiment of rice seed was carried out in order to determine the coefficient of the model of safe drying temperature of rice seed. The safe temperature during drying that ensure high germination ratio was given. 5) Rice and corn kernel moisture content variation during drying was studied. The results of thin-layer drying experiment indicated that there are two periods in rice drying. The stochastic drying model was developed based on the Two-tanks model and Partial Differential Equation (PDE) model. The physical state of rice kernel in thin-layer drying and fixed bed drying was studied by incorporating stochastic drying model and glass transition state diagram. The equation for calculating the number of kernels which can change to rubbery state during drying was developed. 6) The degradation kinetic model of head rice yield was developed using Artificial Neural Network (ANN). The influence of initial moisture content of rice, relative humidity and temperature of heated air on head rice yield was studied by ANN simulation.