Studies On Structures And Functional Properties Of The Conjugates Of Rice Protein With Exopolysaccharides Extracted From Arthrobacter PS-5

Rice protein(RP)is widely favored for its high nutrition and low hypoallergenic character.It has been confirmed to have better composing of essential amino acids,high value of BV and lower irritability as compared with other plant proteins.However,because of its structure,the solubility of rice protein is very low.So the other functional properties of rice protein were poor,such as solubility,emulsification,foaming and other properties,which limits the promotion and application of rice protein.So it's necessary for the rice protein to be modified.Rice protein was grafted with EPS and maltodextrin(M)through Maillard reaction.In order to improve the value of the rice protein for application,the conditions for grafting,the structure and functional properties of RP-EPS and RP-M grafts were studied in system.The study provide the oretical reference for modification of plant protein.Response surface methodology(RSM)was applied to optimize the processing parameters.The effect of the ratio of raw materials,temperature and initial pH on Maillard reaction products(MRPs)was evaluated.Degree of Graft(DG)was taken as response values.The results shown that the ratio of raw materials(EPS/RP,w/w)was 4.91,at pH 12.04,88.37 ?.Under this condition,the theory of grafting degree was 20.19%.The functional property such as solubility,emulsifying ability,foaming ability and were determined at different pH,which showed that the functionality of the conjugations could be greatly increased by the reaction.The above properties of rice protein-maltodextrin conjugates(RP-M)was analyzed by using the same method.It was concluded that the functional properties of RP-EPS is superior to the RP-M.The structure of the rice protein and its conjugation were analysed,and the mechanism was also primarily discussed.Electrophoresis of RP-EPS indicated the increasing of the molecular weight of the subunits.And the new bands of the conjugation subunits were closer to the upper of separating gel.What's more,PAS stain revealed the existence of EPS in the conjugations.Maximum fluorescence response of RP-EPS were at excitation wavelength of 336 nm and emission wavelength of 420 nm,which were in accordance with fluorescence characteristics of the Maillard reaction product.Fourier transform infrared(FTIR)spectra showed that polymerization of rice protein and EPS via covelant bonds,and HPLC of RP-EPS revealed the production of higher molecular weight material.We found that the monosaccharide composition of EPS was only glucose.Ellman 's method analyzes the content of free sulfhydryl group(-SH)of rice protein and the conjugations.The free sulfhydryl content of rice protein after grafting modified was increased,indicating spatial structure of rice protein was destroyed and stability was increased.Thus the solubility was increased.In addition,it was observed by SEM that the surface structure of the conjugates was different from RP control.The rice protein aggregation was dispersed after grafting.