Effects Of Protein Content On Rice Quality And Gelatinization,Retrogradation Of Rice Flour

As the second largest dry matter in rice,protein content is generally7～14%.Because rice protein is rich in essential amino acids,hypoallergenic and gluten free,it is a high-quality source of plant protein for human body.Although the nutritional value of rice protein is high,it is generally believed that high protein rice has low taste and palatability,and is not favored by the market and consumers.In order to explore the effects of protein on rice quality and the gelatinization and retrogradation of rice flour,the protein contents of high protein Rice Maintainer 4112B and maintainer 4461B were increased by cultivation,and then the effects of protein on rice quality indexes and the gelatinization,retrogradation characteristics of rice flour were discussed.The two maintainer lines were treated with three different concentrations which were 0,4,8kg/667m~2 urea.The grain yield was recorded after threshing.The protein content and protein component content,rice quality and RVA were measured.In order to further explain the effect of protein content on the taste of rice,the rice protein isolated from high protein 4112B was used to form recombinant rice flour with 4112B(low amylose)and Zhenguiai(high amylose).The gelatinization and retrogradation performance parameters of rice flour were determined when the protein addition was 0,6,12%(w/w)respectively.The main results are as follows:1.With the increase of protein content,the milled rice rate and whole milled rice rate of 4112B(high protein rice)and 4461B(low protein rice)increased significantly,and the CR(chalkiness rate),CD(chalkiness degree),taste value,GC(gel consistency)and alkali spreading value decreased.Protein content was positively correlated with milled rice rate and whole milled rice rate,and negatively correlated with taste value,gel consistency and alkali spreading value.The proportion of protein components in rice also affected rice quality:gluten content was significantly positively correlated with milled rice rate and whole milled rice rate,and significantly negatively correlated with taste value,gel consistency and alkali spreading value;The content of globulin and prolamin was negatively correlated with chalkiness;GC was negatively correlated with total protein content,globulin content,prolamin content and glutelin content.2.The increase of protein content in rice flour will reduce the peak viscosity,breakdown value,final viscosity and setback value in RVA spectrum,but the peak time and gelatinization temperature will rise correspondingly.3.The addition of protein in the recombinant rice flour reduced the RVA viscosity parameter of the recombinant rice flour,but increased the peak time.Under the same protein content,the four parameters(peak viscosity,final viscosity,setback value and peak time)in high amylose recombinant rice flour were greater than those in low amylose recombinant rice flour.The gelatinization temperature was determined by the interaction between amylose and protein.The protein added in the recombinant rice flour significantly reduced the gelatinization enthalpy,but increased the peak temperature.The increase of amylose content in the recombinant rice flour resulted in the increase of gelatinization enthalpy and the gelatinization temperature of starch.The addition of protein can reduce the hardness and pore size of gel,while amylose can increase the hardness of gel,but reduce the pore size.In conclusion,the protein content will improve the appearance and processing quality of rice,but will reduce the eating quality of rice.The increase of protein content will also increase the gelatinization temperature of rice flour,reduce the viscosity of rice flour during gelatinization,and reduce the retrogradation of rice flour.