Changes Of Rice Properties During Yellowing And The Effect Of Protein On Physical Properties Of Starch

Rice is one of the most important food crops in China and even in the world.Its yellowing during storage seriously affects the quality of rice.In order to explore the phenomenon of rice yellowing,Longjing 46,Jianzhen 2 and Fengliangyou 6 were selected as raw materials in this paper.The rice was stored at 4℃ 20℃ and 37℃,the chroma value,thermodynamic property and pasting property were measured,and the rice protein was extracted for electrophoresis analysis and solubility determination.In order to study the effect of rice protein on the properties of rice starch,rice protein was added to rice starch at the mass ratio of 0,3%,5%and 7%,and its thermodynamic properties,pasting properties and rheological properties were determined.Through the storage of three kinds of rice,it was found that with the increase of storage time,the rice turned yellow obviously,the light and shade L*decreased with the increase of storage time and storage temperature,and the red green a*and yellow blue b*increased with the increase of storage time and storage temperature.The results showed that with the increase of storage time,the peak viscosity,grain value viscosity and final viscosity increased significantly,and the pasting temperature increased,and the degree of change of pasting characteristics had a certain relationship with storage temperature.The higher the storage temperature,the greater the rise of peak viscosity,grain value viscosity and final viscosity of rice,the higher the pasting temperature.The results showed that the initial temperature,peak temperature,end temperature and enthalpy increased with the increase of storage time.With the increase of storage time,the solubility of rice protein decreased gradually,and the average molecular weight of rice protein increased.The pasting properties of rice starch with different proportion of rice protein were determined.The results showed that with the increase of protein content,the peak viscosity,valley viscosity,final viscosity and retrogradation value of the sample decreased significantly,and the pasting temperature increased significantly.The results show that with the increase of protein content,the starting temperature,peak temperature and end temperature of the sample increase,while the enthalpy decreases.The rheological results showed that the storage modulus and loss modulus increased with the increase of frequency.The rheological curves of rice starch with different proportion of protein had the same trend.The shear stress increased exponentially with the increase of shear rate,and the shear stress of rice starch with different protein content changed differently.