Characterization Of Gelatinization Of Rice Flour And The Research On Extrusion Processing Methods

Rice flour has been industrially with economics development. Gelatinization of rice flour with high concentration close to that in actual production was explored by capillary rheometer and rotational rheometer as well as ultrasonic wave. The experiment device was built in order to study the process of rice extrusion. The work and the main conclusions of this thesis are as follows:1.The water absorption and hardness of indica rice was tested during soaking. The water content of indica rice which was dried 5h in the oven was 10.21%.The water absorption and hardness of indica rice which was soaked in water with room temperature was stable when soaking time reached 20min.2.Gelatinization of rice flour with high concentration was studied with capillary rheometer and rotational rheometer. The viscosity of rice flour with different concentrations and particle sizes was measured at different temperatures and shear rates using capillary rheometer. The results showed that the viscosity of rice flour significantly increased at 65? which was initial temperature of gelatinization reaching maximum value at 85? which was completion temperature of gelatinization. This was consistent with the results of other methods. Gelatinized paste exhibited lower viscosity at higher shear rate indicating strong pseudoplasticity which was described by Cross equation while Arrhenius equation and Power law equation were used to analyze viscosity with increasing temperature. The viscosity of rice flour with different concentrations and particle sizes was measured using rotary rheometer witch was consistent with the results of capillary rheometer.3. Gelatinization of rice flour was characterized using ultrasonic wave. The ultrasonic velocity of rice flour with different concentrations during gelatinization was varied with temperature. The results showed that the start temperature of gelatinization was 70?. The higher of concentration, temperature and pressure, the faster of gelatinization. The quantitative expression between velocity and specific volume was got by linear fitting method and adiabatic compression coefficient method.4.The physical variations of rice flour at different screw positions was studied by rice flour machine with different process parameters. Optimal condition of rice flour extrusion using high temperature millstone was 400r/min with different types of millstone and process conditions. Physical and chemical changes of rice flour was studied by analyze the state, particle size and degree of gelatinization. Extrusion process of rice flour was divided into four stages including suspended transport, preliminary crushing, grinding strong and pasting.