Studying On Cooking And Eating Quality Of Different Rice Genotypes And Its Response To Nitrogen Treatment

The experiments were tested in the experimental farms of Yangzhou University during 2004-2005 following wheat. 104 japonica cultivars and 16 indica cultivars, originated mostly from the single season rice cropping region in the south China, were applied to investigate their differences in the physico-chemical characters, RVA profile, taste value and sensory parameters among different N level (0, 150, 225, 300 kg ha-1). The main results were as follows:(1)The indica genotypes exhibited higher protein content and amylase content, shorter gel consistency than japonica genotypes. The medium japonica cultivars exhibited higher protein content, lower amylase content than late japonica cultivars. Among japonica genotypes , the order of gel consistency was medium-maturing medium japonica > late-maturing medium japonica>early-maturing late japonica>early-maturing medium japonica>medium-maturing late japonica.With extension of the growth duration, the protein content of the medium japonica cultivars decreased amylase content inversely, while no obvious difference among cultivars was found for gel consistency. The gel consistency of late japonica cultivars became shorter with the growth duration prolonging, while no obvious difference among cultivars was found for protein content and amylase content.The negative significant correlation between protein content and taste value of all genotypes was observed. With the elevated nitrogen level, protein content increased and cooking and eating quality descended. With extension of the growth duration, protein content decreased and cooking and eating quality improved.Amylase content showed a tendency to decrease with the elevated nitrogen level. Amylase content was not related to taste value remarkably, negatively correlated significantly with gel consistency and breakdown, positively correlated significantly with set-back. The cultivars which had higher amylase content were harder.Among N-fertilize treatments, gel consistency of all genotypes became shorter with the elevated nitrogen level, but the changes of each genotype were difference. There was positive significant correlation between gel consistency and test value. With the elevated nitrogen level, gel consistency shortened and cooking and eating quality descended.Generally speaking, protein content and amylase content was much more influenced by nitrogen fertilizer level, and gel consistency was influenced by genotype much more.(2)The indica genotypes exhibited higher peak viscosity, cool viscosity and set-back than japonica genotypes. There was no obvious difference among japonica genotypes for RVA profile characteristics.With N-application improved, peak viscosity, hot viscosity, breakdown and cool viscosity of all genotypes decreased, set-back and pasting temperature increased for all genotypes. A positive significant correlation was found between breakdown and taste value. Taste value negatively correlated significantly with hot viscosity, cool viscosity, set-back and pasting temperature. According to RVA profile characteristics, rice cooking and eating quality showed a tendency to descend.The coefficient of variation among N-fertilize levels was obviously higher than the coefficient of variation among genotypes for peak viscosity and breakdown, which was contrary for cool viscosity. Among RVA profile characteristics, the coefficient of variations among N-fertilize levels and genotypes of set-back were the highest and which were the lowest for pasting temperature. The coefficients of variation among genotypes of hot viscosity, cool viscosity and pasting temperature increased with the elevated nitrogen level.(3)The differences among N-fertilize levels and genotypes of taste value were significant, and the effect of N-fertilize level was obviously greater than genotypes. The taste value of indica genotype was lower than japonica genotype under medium N-fertilize level and high N-fertilize level. The taste value decreased with the elevated nitrogen level of all genotypes, which showed a tendency to increase with extension of the growth duration for japonica genotypes. The coefficient of variation among genotypes increased with the elevated nitrogen level, but which was obviously lower than the coefficient of variation among N-fertilize levels.(4)Under this experiment condition, the order of influence degree by N-fertilize of cooking and eating quality indexes was set-back>taste value>protein content>breakdown>peak viscosity>amylase content>hot viscosity.It showed that it was feasible to improve cooking and eating quality by adjusting N-application sensibly in production.(5)The tasting integrated grades of cultivars through sense analyzing positively correlated significantly with amylase, gel consistency, peak viscosity and breakdown, negatively correlated significantly with protein content, set-back and pasting temperature, was not related to hot viscosity and cool viscosity remarkably. The order of correlation degree among these indexes was protein content>pasting temperature>set-back>breakdown>peak viscosity>gel consistency.Rice tasting integrated grades of all genotypes showed a tendency to decrease with the elevated nitrogen level. Increasing N-application made the rice cooking and eating quality descend, which was the same as the result of taste instrument analysis. It indicated that analyzing rice cooking and eating quality by taste instrument was a feasible method.(6)According to the analysis by main cooking and eating quality indexes and the classification by taste value and tasting integrated grade, the varieties that showed superior cooking and eating quality were as follow:yanjing2,zhengdao88,xuyou201,shuijing3,guanglingxiangjing,zaofeng9,wu2401,suxiangjing1 and wuxiangjing14 under low N-fertilize level; wuyujing3 and suxiangjing1 under medium N-fertilize level; lianjiajing1,wuyujing3,wunongzao and 99-295 under high N-fertilize level. These varieties were proper for corresponding N-application condition in rice production in Jiangsu.(7)On the basis of their response to N–fertilize levels, varieties in common use in Jiangsu area could be roughly classified into three groups: insensitive genotype, intermediate genotype and sensitive genotype, so that to provide basis for adjust N-application according to varieties.