Milling method and crude protein concentrations of genkei milled rice and toukou milled rice for sake brewing using a horizontal type rice-milling test machine

Abstract

Genkei milled rice has the same ratio as brown rice among major, intermediate, and minor diameters. Toukou milled rice has three diameters which are caused by grinding brown rice with equal distance for each of the three diameters. Crude protein concentrations of four kinds of milled rice which were different in the shape and included genkei and toukou milled rice were compared at 90, 80 and 70 % true milling yield for the purpose of determining the superiority of genkei and toukou milled rice in the concentrations. Shapes of milled rice were evaluated using a diagram which indicates flatness and elongation on the x-axis and y-axis, respectively. Shape properties of genkei and toukou milled rice were investigated in the diagram. Decision methods for genkei and toukou milled rice were proposed using statistical confidence interval of the size and shape of the rice grain, and they were successfully milled at 70 % true milling yield using a test milling machine by proper selection of the rotational frequency of the roll. No difference between genkei milled rice and the most spherical milled rice in the concentration was recognized. No difference between toukou milled rice and the flattest milled rice in the concentration was recognized. The concentration of toukou milled rice was lower than that of genkei milled rice because of the flatter and more elongate shape of toukou milled rice.