Effect of Milling Processes on Quality of Rice Flour
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Abstract:
To investigate the influence of semi-dry milling on the quality of rice flour, different types of grinders were used in this study to prepare quenched rice. The damaged starch, particle size distribution, microstructure, hydration characteristics, differential scan`ning calorimetry (DSC) thermal properties, and rheological properties of milled flours were analyzed, so as to select the appropriate quenched flour with similar characteristics to those of wet milled flour. The results showed that semi-dried milling using cyclone and Buler mills had a significant effect on the quality of rice flour. With increasing tempering moisture content, semi-dry milling led to significant decreases in the damaged starch content, as it was reduced to less than 5%. The particle size also decreased with a cyclone mill; 30% of the rice flour had an average particle size of 54.83 μm, ranging from 12.96 μm to 104.70 μm. Starch particles had an intact structure, which was closer to that obtained with wet milling. At the same time, the water solubility of the quenched rice flours also decreased. In regard to the DSC thermal properties, the pasting temperatures To and Tp decreased, while the pasting range, Tr, and gelatinization enthalpy, ΔH, increased. In regard to the rheological properties, elastic properties represented by G ' and viscosity properties represented by G " exhibited similar changes and were also closer to those obtained with wet milling. Considering the milling process operability, cyclone milling with 30% quenched rice was applicable in the production of rice flour used to make rice noodles.
