Study On The Influence Mechanism Of Rice Water Migration Caused By Different Hot-air Drying Conditions On Its Quality

In order to understand the impact of the intensity and method of water migration in the drying process on rice quality,this topic useed three different drying methods to dry rice:constant temperature continuous drying,constant temperature drying-tempering and low temperature drying-high temperature tempering.The compound rice Guqingliangyou 225 and Huanghuazhan,fresh rice Aolongsi seedlings and Shengtaiyou 018 were dried.The dried rice was divided into four equal pieces according to its long diameter,used LF-NMR to determine the moisture content and water state of the rice,texture analyzer and taste meter to determine the eating quality of rice,EPR to determine molecular mobility and free radicals.Therefore,the influence of the intensity and mode of water migration during the drying process on rice quality was analyzed.The main results and conclusions were as follows:During the drying process,the moisture content and moisture state of rice changed significantly.After drying,the degree of tight bonding between bound water and macromolecules was strengthened.Constant temperature continuous drying treatment resulted in the largest difference in water gradient between the four equal parts of rice.Among the several rice varieties studied,Shengtaiyou,which has the smallest difference in water gradient between the four equal parts of rice,had a difference of 2.12.It showed that the moisture migration of constant temperature continuous drying treatment was very intense,which was not conducive to the internal moisture balance of rice.The low temperature drying-high temperature tempering treatment could minimize the difference in water gradient between the four equal parts of rice.Qingliangyou 225,which had the largest difference in water gradient between the four equal parts of rice,had a difference of only 1.79.This showed that the low temperature drying-high temperature tempering drying treatment had relatively mild moisture migration,which was beneficial to the internal moisture balance of rice.The water gradient difference of each part of the four equal parts of the constant temperature drying-tempering drying treatment was between the above two treatments.The same phenomenon could be observed from the changes of semi-bound water and free water in each part of the rice quarters after the above three treatments.The data showed that the intensity and state of water migration in the drying process of rice were closely related to its quality.The subject of the subject was to study the changes in the quality of rice,such as the increase rate,roughness,texture and taste of the rice after drying,and to study how the water migration of the rice affected the change of its quality.The results showed that the bursting rate of the waist after constant temperature continuous drying was the highest,which was 1.67-9.33%higher than that of low temperature drying-high temperature tempering,and the lowest roughness rate.At the same time,the amylose content increases.The elasticity,hardness and chewiness of the rice during drying were all the upward trend,compared with other drying treatments,the increase in elasticity and chewiness of rice was the smallest,and the increase in hardness was the largest.The appearance,taste and comprehensive score of the constant temperature continuous drying treatment of rice were significantly lower than other drying treatments.The data results showed that different drying treatments lead to differences in the water migration of rice,which could ultimately be reflected in the quality changeed such as the rate of increase in the burst,the roughness,the texture and the taste of the rice.The subject studied the changes in the protein molecular structure,microstructure,molecular motion,number of free radicals and other parameters of the rice after drying,and studied how the water migration of rice affects its quality changes.The results showed that during the drying process of rice,the protein secondary structure changes showed that the proportion of α-helix and β-sheets decreased,and the random coils and β-turns increased.Constant temperature continuous drying treatment resulted in the most dramatic changed in its secondary structure.Among the rice varieties treated with this drying method,Shengtaiyou 018 had the smallest change,but it also reached 4.4%.Compared with the other two drying methods,the low temperature drying-high temperature tempering drying treatment minimized the change in the secondary structure of rice protein.Among the rice varieties treated by this drying method,Qingliangyou 225 had the largest change,but only 3.97 percentage points.Compared with the other two drying methods,the low temperature drying-high temperature tempering drying treatment made the cracks in the rice grains increase and widen,the viscosity and rotation-related time decrease were the smallest,and the increase in molecular movement and free radical intensity was the least obvious.The data results showed that different drying treatments lead to differences in the water migration of rice,which could ultimately be reflected in the changes in the protein molecular structure,microstructure,molecular motion,number of free radicals and other parameters.Combining research and analysis,it was preliminarily summarized that the influence mechanism of water migration caused by different drying methods on rice quality is:the intensity and mode of water migration during the drying process of rice significantly affected the distribution,structure,binding capacity,exercise performance and free radical quenching effect of various biomolecules in rice.The above changes would affected the physical and chemical indicators and microstructure of rice,and ultimately affected the processing quality and sensory quality of rice.