Study On The Interaction Between Modified Rice Dreg Protein And Xanthan Gum And The Emulsifying Properties Of Its Complex

Rice dreg,a by-product of rice starch sugar production,contains a large amount of protein,but its poor solubility limits its application in food industry.The interaction between protein and polysaccharide can greatly improve the structural and functional properties of protein.In this paper,the highly soluble modified rice dreg protein(MRDP)obtained by enzymatic modification was taken as the research object,the interaction between MRDP and xanthan gum(XG)was discussed,and the influence of the interaction between MRDP and XG on the stability of emulsion was studied in combination with the preparation method of emulsion and salt ion concentration.Firstly,MRDP was compounded with XG(0-0.3 wt%)to study the phase behavior of the composite system at various pH values.Turbidity,apparent characteristics,average particle size and ζ-potential showed that with the increase of XG concentration,the composite system tended to be stable,and MRDP and XG were more likely to form complexes at pH 3 and 4.When the concentrations of pH 3 and XG were ≤0.05%,composite condensates were formed,and soluble complexes were formed in other cases.The data of fluorescence spectrum,ultraviolet spectrum and infrared spectrum show that the interaction between MRDP and XG includes electrostatic interaction,hydrophobic interaction and hydrogen bond.When pH was 3,electrostatic interaction plays a leading role,and when pH was 4,hydrophobic interaction and hydrogen bond play a stronger role.Then,the effect of preparation method on the stability of MRDP-XG emulsion at pH 4 was studied.The results showed that with the increase of XG concentration,the average particle size of layer by layer emulsion remained at 60 μm,while the particle size of the mixed emulsion decreased first and then increased.When the addition amount of XG was 0.1 wt%,the average particle size of the mixed emulsion was the smallest(30.60 μm).Under the two preparation methods,the storage stability of the emulsion increased with the increase of XG concentration.After 20 days of storage,when the XG concentration was 0.3 wt%,the milk precipitation index of the mixed emulsion was the lowest(6.31%),while the layer by layer emulsion does not appear stratification.The results of centrifugal stability showed that the mixed emulsion after centrifugation was relatively stable,and the layer by layer emulsion had serious oilwater separation.On the whole,the stability of the emulsion obtained by the mixed preparation method was better than that by the layer preparation method.Finally,the effects of salt ion concentration on the interaction of MRDP-XG and the stability of emulsion prepared by mixed preparation method under pH 4 were studied.The results showed that the turbidity and particle size of the composite system gradually decrease with the increase of salt ion concentration,and the change of the composite system with XG addition of 0.3 wt%was small,indicating that salt ions will destroy the interaction between MRDP and XG in aqueous solution.The lower the concentration of XG,the more obvious the destruction effect.In the study of emulsion,with the increase of salt ion concentration,the stability of emulsion without XG and 0.3 wt%XG decreased,while the stability of emulsion with 0.1 wt%XG increased first and then decreased.When the salt ion concentration was 50-150 mmol/L,the stability of the emulsion with the addition of XG of 0.1 wt%was better.