The brown and white rice samples were obtained by the hulling in a rubber roll mill followed by their milling in a rice polisher for 30 s to separate the bran.
The time of polishing was set by performing trials at different periods of time. The grains were cleaned manually by removing all foreign matter such as dirt, stones, and broken rice. The rice recovery (hulling and milling), brown rice, white rice, brokens, husk, and bran were determined during processing of paddy to white rice.
The selection of vertical and horizontal machine to design has large effect on the head rice yield and vertical design is mostly preferred. The optimum moisture content of paddy rice for milling process was reviewed and it is observed to be varied according to the variety of rice grain and it had the least rice breakage when using three abrasive whiteners in series followed by one friction whitener as a polisher. As the cylinder speed increase from 600 to 1000 RPM, the percentage of broken kernels approximately gets doubled.
After paddy separator, brown rice/husk/paddy passed through husk separating step, which is separating husk (lighter in density) from the rest (heaver density). This can be done by sieve or ventilation. There are many machines and methods designed to remove bran from the rice. The Japanese milling system is most often used in the most modern mills. With this system, the rice is first passes through a milling chamber that has an abrasive stone spinning in the center and a scarified metal screen on the outside. (The abrasive system).