RADIAL DISTRIBUTION OF PROTEIN BY SOLUBILITY CLASSES IN MILLED RICE KERNEL

Radial distribution of the four solubility classes of protein was determined for eight varieties of milled rice. Five consecutive layers of the kernel, totaling about 10% by weight, were removed by abrasive milling. Original and residual kernels, and all flours, were percolated successively with water, 5% sodium chloride, and 60% ethanol to remove albumins, globulins, and prolamins; glutelins were calculated by difference. Albumin and globulin were concentrated in proteins at the surface of all rices; concentrations decreased toward the kernel center. Globulin generally was somewhat less concentrated than albumin in the outer kernel layers and had less steep gradients toward the center. Globulin and albumin gradients differed independently among varieties. The limiting amino acid, lysine, occurred in 12% greater concentration in the protein of the outer layer of Calrose rice than in the protein of the total kernel. © 1968, American Chemical Society. All rights reserved.