Influence of operating parameters on the milling quality of long-grain white rice

The current study aimed to test and evaluate sheets' different perforation shapes, brake angles, and milling durations to improve the quality of long-grain white rice from an abrasive milling machine. The investigated parameters of head rice yield, broken rice percentage, whitening degree, and rice bulk temperature were influenced by five sheets with five perforated shapes (horizontal, vertical, inclined, 1 mm round holes, and 1.5 mm round holes), three brake angles (0, 45, and 90), and four milling durations (60, 70, 80, and 90 s). The results showed that the horizontal rectangular perforated sheet resulted in the highest value of head rice yield and the lowest value of broken rice. On the other hand, the vertical rectangular perforated sheet resulted in the highest whitening degree, followed by the inclined rectangular perforated sheet. The round holes (1.0 mm and 1.5 mm diameter) are not recommended for the long-grain whitening process because of the resulting high values of broken kernels, rice bulk temperature after the whitening process, and lower values of whitening degree. The brake angle of 90 resulted in the highest value of broken rice for all studied perforated sheets used in this study. This study recommended that the optimum operating conditions were using the horizontal rectangular perforated sheet, zero degree brake angle and milling duration of 80 s.