Effect of hulling and milling on the physical properties of rice grains
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Department of Food Science and Technology, Ferdowsi University of Mashhad (FUM), P.O. Box. 91775-1163, Iran
Int. Agrophys. 2008, 22(4): 353–359
Basic physical properties of agricultural materials play important role for optimizing the design of equipment and facilities for the harvesting, handling, conveying, separation, drying, storing, and processing. In this study, some physical properties of three rice varieties, namely Tarom Mahali, Fajr, and Neda, at three levels of processing, which name rough rice (paddy), brown rice (husked or hulled), and white rice (milled) were investigated. The thousand grains mass and porosity decreased significantly with the rice processing, but the bulk density increased. The rough rice of each variety showed the least value of true density. Unit mass and volume of rice grain decreased with the rice processing. Totally, the static coefficient of friction affected by cultivars, levels of processing, and frictional materials. By processing, the filling angle of repose for all cultivars decreased. The terminal velocity increase significantly for every variety. It was observed that the terminal velocity of the rice’s hull and bran is lower than for the rough rice, brown rice, milled rice.