Regulation On Eating Quality Of Japonica Rice

Rice is one of the most important food crops in China,feeding more than 65%people in china.Increasing rice yield is very important to food security.Overuse of water and fertilizer in rice production produces negative effect on rice quality.With the improvement of people’s living standard,the demand for high quality rice is urgent.Eating quality refers to the sensory impression that rice gives to the mouth and taste,when observing and chewing rice.The eating quality,the main factor for consumer purchasing decisions,is difficult to be studied due to its complex physicochemical foundations.This study aims to investigate the effect of high-yielding practices on rice eating quality,performing two filed experiments including nitrogen fertilizer rates and cultivation patterns.The main findings are shown as follows.1.The effects of nitrogen fertilizer rates on eating quality and its physicochemical foundations were investigated.Four rice cultivars grown in Jiangsu province,two mutants mutagenized by Wuyujing 3 and a indica-japonica hybrid rice "Yongyou 1540"were used as materials.Three nitrogen fertilizer rates(CK,N5-5,N10-0)were conducted.(1)Single basal application of urea,sensory evaluation showed that there was no significant difference in aroma,color and luster among the cultivars.The stickiness increased in Yongyou 1540 but decreased in Wuyujing 30;hardness increased in Wuyunjing 30 and Ningjing 5.Meanwhile,protein content increased,peak viscosity and breakdown value decreased.(2)Increase of the percentage of panicle fertilizer,the aroma,color,luster,elasticity and integrated value of rice taste decreased obviously,the hardness increased.Starch content,and amylopectin content decreased.;protein content increased.The peak viscosity,hot paste viscosity and enthalpy of gelatinization decreased significantly.(3)This study showed that high nitrogen input mainly increased protein content,decreased viscosity of rice flour gel,and finally led to the deterioration of eating quality.2.The effect of high-yielding practices on eating quality and its physicochemical foundations were investigated..Xudao 8 was used as material,and three cultivation patterns(the conventional pattern,high-yield cultivation pattern and integrated pattern)were conducted.(1)In terms of yield,three cultivation schemes reached the same level.On milling quality,head rice rate is highest in the integrated pattern of water and fertilizer.Compared with the other two patterns,protein content of the high yield cultivation pattern increased,and the total starch and amylopectin decreased obviously.,Peak viscosity and hot paste viscosity of the conventional scheme are the highest.(2)In sensory evaluation,integrated value of rice taste of high-yield cultivation pattern was lowest but highest of integrated pattern.(3)The study showed that starch,amylopectin and the viscosity parameters decreased,protein content increased,which were the key factors leading to the deterioration of eating quality.3.Correlation analysis between eating quality and physicochemical parameters were performed.The total starch and amylopectin were positively associated with eating quality.Protein and its components were negatively associated with eating quality.No significant correlation have been found between fat and eating quality.Peak viscosity was positively associated with integrity,viscosity,springiness and the integrated value of rice taste;and breakdown viscosity were positively associated with springiness and integrated value of rice taste;gelatinization temperature and enthalpy were negatively associated with integrated value of rice taste.In summary,protein content increased and starch viscosity parameter decreased with the high water and fertilizer inputs,resulting in the deterioration of eating quality.The total starch and amylopectin were positively associated with eating quality,but no significant correlation between amylose and eating quality.The peak viscosity,hot paste viscosity and breakdown value were positively associated wit eating quality.Gelatinization temperature and enthalpy were negatively associated wit eating quality.Comparison of different eating quality evaluation methods,physicochemical parameters can not accurately reflect the eating quality.Sensory evaluation is still the most direct and the most believable.