Relation between Eating Quality and Chemical Components in Milled Rice and Amino Acid Contents in Cooked Rice

Abstract

To clarify the relation between the eating quality and inorganic chemical components in rice kernels or amino acid content in cooked rice, the authors collected 18 cultivars from inside and outside Japan. Eleven cultivars out of them were examined in terms of sensory test by "the visitors at the May festival" of the University of Tokyo. Experimental results showed that the evaluation of sensory test coincided with the evaluation by an expert panel of "Japan Cereals Inspection Association". Cultivars that had a high eating quality had a lower amylose and nitrogen content in their kernels. On the other hand, cultivars that had low evaluation showed a higher amylose and/or nitrogen content in kernels. Amounts of amino acid exuded from cooked rice showed a specific patttern in the total amount and the ratio of them to the total one. Namely, cultivars that had a high eating quality in japonica type rice, had a low level of free amino acid and comparatively higher rate of glutamic acid and aspartic acid. In principal component analysis, amylose and nitrogen content showed a large factor loading of primary component, and both primary and secondary factors loading of asparagine, aspartic acid, alanine and sarcosine showed positive values. However glutamic acid and aspartic acid showed positive rate of contribution to eating quality in multiple regression analysis. From these results, it was estimated that glutamic acid and aspartic acid content might be responsible for improving of eating quality of rice kernels as well as amylose and nitrogen content.