Grain and Starch Properties of Waxy and Low-Apparent Amylose Philippine Rices and of NSIC Rc222

摘要

Waxy and low-apparent amylose content (AC) rices with intermediate gelatinization temperature (GT) by alkali spreading value (ASV, 3-4), recently observed in farmers' specialty rices and in the Philippine rice breeding program, were shown to have high GT by differential scanning calorimetry (DSC). Such rices have harder cooked rice texture, especially upon staling, than low-GT entries and were closer to high-GT rices in properties. They have identical amylopectin chain ratios and starch synthase Ha (SSlla) alleles as high-GT rices. An improved method for AC determination of waxy rice employed a longer standing time of 2 h to reduce amylopectin-iodine interference at alkaline pH and was used for the waxy rices in this study. NSIC Rc222 with harder cooked rice than other intermediate-AC intermediate-GT rices was verified to be high-AC by DSC AC value and Waxy (Wx) alleles, had higher content of long-chain amylopectin and its viscosity properties were closer to high-AC rice. Wx alleles were, in general, useful for verifying the colorimetric AC classification of Philippine rices, i.e., waxy or low-AC: 17-20TAC; intermediate-AC: 17GCC or 20GCC; and high-AC 8, 10, or 11GAC or GAT. Also, SSlla alleles differentiated waxy and low-AC Philippine rices into high-GT and low-GT only.