RICE QUALITY AND PROCESSING Impacts of Thickness Grading on Milling Yields of Long-Grain Rice

As variations in kernel uniformity can affect rice milling performance, limited thickness-grading to remove thin kernels was evaluated for effects on milling yields. Along with unfractioned (UNF) rice of four long-grain cultivars, rough rice was mechanically sieved, resulting in two thickness fractions, Thick (>0.079 inch) and Thin (<0.079 inch). Milled rice yield (MRY) and head rice yield (HRY) were determined for each cultivar/fraction. Thickness grading resulted in between 67% and 90% Thick kernels. Milled rice yield of Thick kernels was greater than that of Thin kernels, and were generally greater than UNF. Moreover, HRYs of Thick kernels were greater than both Thin and UNF. Thickness-grading improved milling-yield parameters, and showed a trend for reducing chalkiness of Thick kernels when compared to UNF. Although it would create an extra process operation and flow, benefits to milling yield could justify this procedure.