Iodine Absorption Scanning Analysis of the Digestibility and Gelatinization Properties of Koshitanrei Rice Cultivar for Sake Brewing

摘要

The "Koshitanrei" rice cultivar is grown and widely used for sake brewing in Niigata Prefecture; however, the starch characteristics of this cultivar have not yet been elucidated. Therefore, we investigated the influence of starch properties on the gelatinization properties and digestibility of this cultivar, which are very important in sake production. Starches of rice samples milled to 60 % yield from "Koshitanrei," "Yamadanishiki," "Gohyakumangoku," and "Koshiibuki" were subjected to iodine colorimetric scanning analyses and pasting properties were investigated using a rapid viscosity analyzer. The correlation between iodine absorption and digestibility was analyzed following steaming of the rice samples. The findings of our study showed that the maximum wavelength of the iodine absorption curve (lambda max), which is derived from the chain length distribution of amylopectin, of Koshitanrei was the same as for Yamadanishiki, followed by Gohyakumangoku and Koshiibuki. Further, we found that lambda max was significantly correlated with enzyme digestibility. The results of our study show that enzyme digestibility can be estimated by a simple evaluation method, that is, iodine absorption scanning analysis.