Influence of Thresher Cylinder Speed and Grain Moisture at Harvest on Milling Yield of Rice

The percentage of broken rice (Oryza sativa) kernels was determined after threshing the grain at varying cylinder speeds of the thresher and moisture contents of the grain at harvest. Moisture contents of the individual grain samples ranged from 12 to 26% and the two cylinder speeds were 600 and 1000 RPM. Significant differences between germplasm, cylinder speed and moisture content of the grain at harvest on milling yield was observed. For example, Newbonnet had the fewest broken kernels while Leah had the greatest amount of broken kernels. Lemont produced the highest total milling yield; whereas, L202 produced the lowest total milling yield. Newbonnet produced the highest and Leah produced the lowest head rice yield. Percentage of broken kernels approximately doubled when the cylinder speed was increased from 600 to 1000 RPM. Generally there was a significant increase in the percentage of broken kernels as the moisture content of the grain at harvest decreased