Studies on Diagnosis of Rice Grains by Photometric Method : III. On the quality inspection of hulled glutinous rice

Abstract

A photometric method for evaluating the quality of hulled non-glutinous rice grains has been reported by the author. In this experiment, an application of this method to hulled glutinous rice was examined. Glutinous rice, especially the grade standard samples from various prefectures throughout the country were also tested photometrically. Injured grains which are characterized by abnormal color in pericarp or chalky tissues in endosperm showed low light transmittancy in accordance with the degree of injury. Glutinous rice samples of high grade showed high values of the relative light transmittance and low percentages of injured or inferior grains. Therefore, close relationships among the grade of rice, content of injured or inferior grains and the relative light transmittance values were seen as revealed on the non-glutinous rice in the previous report. A significant correlation was also obtained between light transmittance values of the glutinous rice samples and those of the normal or healthy grains selected from the same samples. From these results it was confirmed that this photometric method could be reasonably applied to evaluating the quality of hulled glutinous rice. As for the standard rice samples from various prefectures, these coefficients of variance in the transmittance values were bigger for each of the grades as compared with nonglutinous standard rice. This suggests that national consistency in quality standard of glutinous rice is unsatisfactory. Mixing nonglutinous grains with glutinous samples increased the transmittance value of the samples considerably. Therefore, a previous inspection of mingled nonglutinous grains which can be done easily with the naked eye may be necessary for a correct evaluation of glutinous rice by photometric method.