Impacts of Kernel Thickness and Associated Physical Properties on Milling Yields of Long-Grain Rice

Abstract

Abstract. Rice milling yields are impacted by kernel physical properties, which may vary by kernel thickness. Four rice lots, comprising Wells and XL753 long-grain cultivars of both superior and inferior milling yields, were thickness graded into three fractions: thin ( 2.05 mm). Milled rice yield (MRY), head rice yield (HRY), rough-rice bulk density (I b ), and both brown-rice chalky area (chalkiness) and fissured-kernel percentage (FKP), were determined for each lot and fraction. The MRYs of thick kernels exceeded those of thin kernels for all lots, and those of medium kernels for inferior lots. The HRYs of thick kernels were less than those of medium kernels, significantly so for inferior lots. For all lots, medium kernels had greater HRYs than thin kernels. Thick kernels had greater HRYs than thin kernels for three of the four lots evaluated. Overall, I b increased, and chalkiness decreased, with increasing kernel thickness. The FKP varied by cultivar, increasing with increased thickness for only the Wells lots. Using uni-variate linear modeling, I b effectively predicted MRY (R 2 =0.91, P 2 =0.14, P 2 =0.25, P 2 =0.24, P 2 =0.46, P b , chalkiness, and FKP, improved the prediction of MRY (R 2 =0.93, P 2 =0.83, P