Preparation,Funcitonality And Structure Of Rice Protein Modified With Deamidationa And Maillard Reaction

Rice protein is an abundant protein rescoure in China.It has high-value nutrition,low allergy and good palatability.But rice protein contains a large number of amide groups which may result in a compact molecule structure through hydrogen bonding,thus leading to the poor behaviour in solubility,emulsification and foamability.Deamidization and Maillard reaction are common method to improve the functional properties of insoluble food protein.In this study,rice protein is co-modified by deamidization and Maillard reaction to improve its functional properties.(1)Deamidized rice protein was prepared with acid.The effect of the variety of acid,acid concentration,protein dispersion concentration,temperature and time on solubility,hydrolysis degree and deamidization degrees of deamidized rice protein were studied.The optimum parameters were obtained as below:HCl concentration 0.3 mol/L,protein dispersion concentration 4.5%,reaction at 85℃for 3 h.The solubility in water at neutrall pH,emulsification and foamability of deamidized rice protein were obviously enhanced.(2)Structure of deamidized rice protein was chareacterized through polyacrylamide gel electrophoresis,Fourier transform infrared spectrum,differential thermal scanning,scanning electron microscope,surface hydrophobicity and free sulfhydryl content.As deamidization degree increased,its surface hydrophobicity exhibited a trend of first decrease and then increase;while the contrary trend was found in the free sulfhydryl content of deamidized rice protein.Thermal stability of rice protein was improved by acid-deamidization.SDS-PAGE profile indicated low molecular weight in the modified proteins.The result of scanning electron microscope showed its microscale was reduced,suggesting a more flexible protein structure.(3)Marllard reaction products of deamidized rice protein was prepared with maltodextrin.And the effects of deamidization time,protein dispersion concentration,amino group-carbonyl group mole ratio,temperature,p H and time on were deamidized rice protein MRPs were studied.The optimum condition were obtained as below:deamidization time 2 h,protein dispersion concentration 2.25%,amino group-carbonyl group mole ratio 1:6,p H10.0,and reaction at 80~oC for 2h.(4)Functional properties of deamidized rice protein MRPs were investigated in this study.The results showed that the functional properties of deamidized rice protein MRPs were improved significantly.But as Maillard reaction time prolonged,no difference was observed the functional properties of in deamidized rice protein MRPs.(5)Structure of deamidized rice protein MRPs was characterized.Covalent crosslinking was found between deamidized rice protein and maltodextrin,as evidanceding by SDS-PAGE and FTIR.Its thermal stability was enhanced and its thermal denaturation collaboration was reduced.By the method of scanning electron microscope,microstructure of deamidized rice protein was decomposed by Marllard reaction.