- 日本土壌肥料学雑誌 (ISSN:00290610)
- vol.67, no.2, pp.139-146, 1996
One of the main factors determining the taste of cooked rice grain is the protein content in the polished grain, usually high-taste grains have a low protein content. In the rice grain, two protein bodies, PBI and PBII are included. Glutelins are in PBII, and prolamins are in PBI which is not digested by pepsin. A recent interest is which proteins have a greater influence on the rice taste. In this study, several varieties of rice were cultivated with different treatments of nitrogen ranging from 0 to 12 gm^<-2> and the effect of these nitrogen treatments on the protein contents in the grain was investigated. The proteins in the polished rice(polishing yield of 90%)were analysed by the extraction method including the pepsin digestion. Prolamin was the residual proteins after pepsin digestion. The contents of albumin(water-soluble protein)+ globulin(salt-soluble protein), glutelin and prolamin were increased with increasing nitrogen fertilizer particularly by late application, but the proportions of the individual proteins in the total protein were almost constant at any nitrogen treatment. However, the percentages of prolamin in the total protein changed with varieties and years. They were about 18% in Takanari, an indica variety, and about 10% in Koshihikari and Kinmaze, japonica varieties, in 1994, and those in Koshihikari were 10.0-11.2% in 1991 and 1994, and 6.2-7.3% in 1990, 1992 and 1993. They were lower in unfilled rice(brown rice size below 1.8mm)than in filled rice(more than 1.8 mm)and were lower in the inferior spikelets that the superior spikelets when examined in Koshihikari. Since prolamins accumulate in the later stage of grain filling than gluatelin, it is inferred that the grains which mature late have the low prolamin fraction.