IMPACTS OF THICKNESS GRADING ON MILLING YIELDS OF LONG-GRAIN RICE

摘要

As kernel dimensional-variability can adversely affect milling yield and quality of rice, limited thickness-rading to remove thin kernels was evaluated. Along with unfractioned (UNF) rice, rough rice was mechanically sieved, resulting in two thickness fractions, Thick (> 2 mm) and Thin (<2 mm), of four currently-produced, long-grain cultivars. Milled-rice yield (MRY), head-rice yield (HRY), lipid and protein content, bulk density, and milled-rice chalkiness were determined for each cultivar/fraction. Thickness grading returned between 67% and 90% Thick kernels. MRYs of Thick kernels were greater than Thin, and trended greater than UNE Moreover, HRYs of Thick kernels were greater than both Thin and UNE For Thin, greater total lipid and crude protein content, and lower bulk density, suggest incompletely-filled kernels. Thick kernels had less chalkiness than Thin, and trended to less chalkiness compared to UNE Thickness-grading improved milling-yield parameters of Thick, and showed promise for reducing chalkiness. Although thickness-grading to remove the Thin kernels would create an extra process operation andflow, benefits to milling yield, and to improved visual perception through reduced chalkiness and greater kernel uniformity, could justz:bi this procedure.