Concentrations Of Lipids In Grains Of Japonica Rice: In Response To Nitrogen Fertilizer And In Relation To Physicochemical Properties Of Rice Flour

In present study, three groups including six japonica cultivars ningjingl, ningjing2, zaofeng9, xudao4, wuyujing3, and wuyunjing7 and seven nitrogen treatments (CK, L82, L55, M82, M55, H82 and H55; CK, L, M, H means 0,90,180,270 kg N ha-1, respectively, and 82 and 55 means the ratio of basical and panicle fertilizer is 8:2 and 5:5, respectively) were used in year 2008,2009 and 2010 to study the relationship between lipid and starch properties and their response to nitrogen. Crude lipid content and components of different genotypes and their response to nitrogen were analyzed in brown rice and milled rice, and the objects of the present study were to investigate the relationship between lipid content and components and cooking and eating quality under different nitrogen treatments, and the relationship between lipid and starch crystal properties.The main results are as follows:(1) The lipid contents and components in brown rice and milled rice were mainly affected by genotype. The results indicated a significant genotypic variation of crude lipids content in brown rice and milled rice, the change of crude lipids content in three groups were different in brown rice but consistent in milled rice. The components of lipids were also significantly genotype different. In comparison with large panicle cultivars, small panicle cultivars had higher or similar crude lipids in milled rice and had higher starch lipids in milled and brown rice. Small panicle cultivars had lower or simillar non-starch lipids in milled rice and brown rice. In comparison with genotype, N had little effect on the content and components of lipid in milled rice and brown rice.(2) The lipid content and components significantly affect the cooking quality of the rice. The results showed that, except Xudao4 in 2008, the amylose content all increased in defatted rice flours. As to RVA characteristics.the mean of 7 nitrogen treatments, after deresination treatments PaT and SBV decreased, PKV, HPV, CPV and BDV all increased,but CSV may decreased or increased that decided by cultivars. After defatting the CSV of ningjing2 and wuyujing3 increased, but the other 4 cultivars all decreased. From these results, we can conclude that defatting treatment had complex effect on the cooking and eating quality, only from this perspective we cannot explain the effect of fat on rice cooking and eating quality. As to the relationship between fat content and components and rice cooking and eating quality, correlation analysis showed that, there was no significant correlation between crude lipids and NSL in brown rice and milled rice and AC. But there was a significantly negative correlation between SL in defatted and undefatted rice and AC in defatted rice. The crude lipid content and SL in milled rice were significantly and negatively correlated to HPV and CPV in undefatted rice, SL in milled rice was significantly and negatively correlated to CVS in undefatted rice. From these results we summary that the lipid content especially the starch lipids content in milled rice was closely related to the cooking and eating quality of rice, the cooking and eating quality of rice were promoted if the starch lipids content in milled rice were increased.(2) Lipids may have a negative effect on the formation of structure of starch crystal. The results demonstrated that all starch samples showed a typical A-type diffraction pattern, but crystallinity and peak intensity were significantly different. Nitrogen had significant effect on starch crystal characteristics. In undefatted rice flours, the crystallinity of all samples firstly increased and then decreased with the increasing amount of the N-fertilizer used. The peak intensities (29=15°,17°,18°and 23°) of high nitrogen treatment (H55) significantly lower than those of the control (CK), low nitrogen (L55) and moderate nitrogen (M55). This demonstrated that appropriate nitrogen would improve the inner structure of starch, but excessive nitrogen would be adverse. Rice lipids had significant effect on crystal characteristics too. In general, the crystallinity of all samples increased after lipids were removed. The changes of intensities of different peak positions in undefatted flours were not consistent with variation in defatted starch samples. All the results showed that lipids may go against the formation of fine structure of starch crystal, and the mechanism were complicated.