Influence of Cropping Season on Lipid Content and Fatty Acid Composition of Lowland Non-glutious Brown Rice

Abstract

The influcnce of cropping season on lipid content and fatty acid composition of brown rice was investigated on six lowland non-glutinous varieties by early, normal, and late season cultures at Chugoku National Agricultural Experiment Station in 1977. The earlier the cropping season, the higher the lipid content and the significant difference between three cropping season cultures was observed. As to the fatty acid composition, the earlier the cropping season, the more the myristic acid, palmitoleic acid, stearic acid, oleic acid, and arachidic acid contents were revealed. On the other hand, the later the cropping season, the more the linoleic acid and linolenic acid contents were revealed. The significance of variation was observed between three cropping season cultures on oleic acid, linolcic acid, and linolenic acid contents and between late and normal season cultures and also bctween late and early season cultures on other fatty acid contents. The daily mean temperature during ripening showed significantly positive correlations with lipid content and myristic acid, palmitoleic acid, stearic acid, oleic acid, and arachidic acid contents and negative correlations with linoleic acid and linolenic acid contents. With respect to the fatty acid composition, there was highly negative correlation between oleic acid and linoleic acid contents. From the regression equations between oleic acid and linoleic acid contents and between ripening temperature and both the fatty acid contents in the previous and this papers, it was shown that the equal value of both the fatty acids was about 38.7% and both the fatty acids come to the same valuc at about 20 to 22°C on the daily mean temperature during ripening.