Starch Structure And Physicochemical Properties Of Rice Varieties With Different Taste And Its Response To Environment

Taste quality is the quality trait that consumers are most concerned about,and therefore the most critical indicator for improving the quality of staple rice.The determining mechanism and influencing factors of rice taste quality are relatively complex,not only closely related to the physicochemical properties of rice starch,but also closely related to the rice processing and cooking processes.Starch is the main component of rice,and a preliminary framework has been formed for the impact of starch physicochemical properties on rice quality.However,research on the starch structure characteristics of high-quality rice,the gelatinization characteristics during cooking,and the characteristic characteristics of high-quality rice starch synthesis is still insufficient,which has led to a lack of accurate understanding of the quality formation characteristics and cultivation performance of high-quality varieties with different characteristic types currently promoted and used,thereby limiting the progress of optimized cultivation techniques.This experiment selected japonica rice varieties with significant differences in rice taste,analyzed the performance characteristics of starch physicochemical properties of rice varieties with excellent taste and their relationship with the formation of good taste.Furthermore,different nitrogen levels,low light and high temperature stress treatments were set during the fruiting stage to observe the differences in starch physicochemical properties,structural characteristics,starch synthesis and accumulation,and their response to nitrogen and ecological environmental factors among rice varieties with different taste.Exploring the relationship between the taste quality of high-quality rice and the starch structure and physicochemical properties of rice,as well as its environmental effects to provide necessary theoretical support for the selection and optimization of high-quality rice varieties and cultivation.The main test results are as follows:1.The taste value of rice was as follows:Jinxiangyu 1>Wuyujing 3>Wumijing>Huaidao 5,which was consistent under different nitrogen levels.Therefore,Jinxiangyu 1 and Wuyujing 3 were classified as good taste rice varieties,while Wumijing and Huaidao 5 were classified as common taste rice varieties.For rice varieties with good taste,the content of amylose and protein is low;the RVA spectrum of starch has high breakdown and low setback,and starch is easy to gelatinize;the processing quality,solubility,swelling power and starch granule morphology are better,and the relative crystallinity of starch is higher.Soft rice has lower amylose content,higher chalkiness,and better taste performance compared to conventional japonica rice.The gelatinization characteristics indicate that soft rice has lower setback and higher breakdown.2.The difference in amylose content in the grains of different taste rice varieties is already evident at the early filling stage.The accumulation of amylose content in the grains of ordinary taste rice is faster at the early filling stage,which may be related to the activity of key enzymes in starch synthesis in rice grains.The GBSS enzyme activity in the grains of ordinary rice varieties is higher,which is conducive to the formation and accumulation of amylose in the grains,while the SSS enzyme and SBE enzyme activities in the grains of excellent rice varieties are higher,which is conducive to the catalytic synthesis of branched starch in the grains.The SSSI isoenzyme activity in the grains of rice varieties with good taste is higher,which is conducive to the synthesis of short chain branched starch in the grains.However,the SSSII enzyme activity in the grains of ordinary taste varieties is higher,which is conducive to the synthesis of medium and long chains in the grains.3.With the increase of nitrogen level at grain filling stage,the taste value of rice decreased significantly,the amylose content decreased,the protein content increased significantly,the gel consistency shortened,the peak viscosity and breakdown in RVA spectrum decreased,and the setback increased;the granule morphology of starch became worse;the gelatinization enthalpy,relative crystallinity of starch increased,while the solubility,swelling power.There are obvious differences between varieties in the response of rice physicochemical properties and taste value to nitrogen.The taste quality of good taste varieties is relatively stable,and the sensitivity to nitrogen is less than that of common taste rice.4.As the degree of weak light stress increases during the fruiting stage,the yield of rice decreases,the processing and appearance quality,cooking and eating quality,and gelatinization characteristics deteriorate;the solubility and swelling power decrease.There are significant differences between varieties in the effects of low light stress on the physicochemical properties and taste value of rice,and the impact of low light stress on the taste quality of excellent taste varieties is smaller than that of ordinary taste rice.Under high temperature stress,rice yield significantly decreases,relative crystallinity increases,cooking and eating quality,gelatinization characteristics,and starch particle morphology deteriorate.5.The determination of starch structure showed that the proportion of short to medium chains in the branched starch structure of fine taste rice was relatively large,while the proportion of medium to long chains and long chains was relatively small.On the contrary,ordinary taste rice had a higher proportion of medium to long chains and long chains in the branched starch structure;the proportion of short to medium chains in soft rice is higher,while the proportion of long chains is lower.The structure of branched starch is closely related to taste quality,with short chain(A-chain)showing a highly significant positive correlation with taste value,while long chain(B3 chain)showing a highly significant negative correlation with taste value.Environmental factors such as increased nitrogen levels or high temperature stress can lead to an increase in the proportion of medium to long chains and long chains of branched starch,while a decrease in the proportion of short to medium chains.However,the impact on good taste rice is relatively small.