Study On The Relationship Between Protein Surface Activity And Surface Hydrophobicity

In this study,soybean proteins were modified by heating treatment,ultrasonic treatment,acid-base treatment,peroxyacetic acid treatment,SDS treatment,urea treatment,enzymatic treatment,phosphorylation treatment and acylation treatment,respectively.The changes in spatial structure,surface activity and surface hydrophobicity of the modified treated soybean proteins were investigated,and the correlation coefficient between surface hydrophobicity and surface activity was analysed.The correlation between surface hydrophobicity and surface activity of the treated soybean protein isolates was found to be significant,and the changes in surface hydrophobicity were positively correlated with the changes in surface activity,which can be used as a key indicator for the evaluation and prediction of the surface activity of protein molecules.The specific results are as follows:(1)Both the spatial structure and surface activity of soybean isolates changed after the modification treatment.The experimental results of circular dichroism,endogenous fluorescence and free sulfhydryl content showed that after different modification treatments,the spatial structure of protein molecules was opened,intermolecular disulfide bonds were broken,the ordered secondary structure was disrupted,the α-helix,β-fold and β-turn angle contents decreased,and new disordered structures were generated;the non-polar groups embedded in the interior were exposed,and the protein spatial structure became stretched and loosened.The change in spatial structure affects the distribution of groups on the surface of the molecule and improves the protein interfacial capacity.experimental results of HLB values show that as the spatial structure is opened up,the lipophilic groups inside the molecule are transferred to the outer surface of the molecule and the overall lipophilicity of the protein molecule increases.The experimental results for surface tension and critical micelle concentration(CMC)values show that as the secondary structure is opened and non-polar groups are exposed,the surface tension decreases and the corresponding CMC values continue to decrease.(2)After modification of soy protein by heat treatment,sonication,acid-base treatment,peroxyacetic acid treatment,SDS treatment,urea treatment,phosphorylation and acylation treatment,non-polar groups were exposed on the molecular surface and protein emulsification and stability were significantly improved;the molecular space structure became loose,resulting in a significant increase in protein foaming and foam stability.After enzymatic treatment,the emulsification and foaming properties of the proteins improved as the degree of hydrolysis increased,while the emulsion stability and foam stability decreased.The results of the pearson correlation analysis between the surface activity and surface hydrophobicity of the treated soybean protein isolate showed that the emulsification and stability and foaming and stability of the treated soybean protein isolate were significantly positively correlated with the surface hydrophobicity(P<0.01),and that the surface hydrophobicity and surface activity of the soybean protein isolate were closely related.The surface hydrophobicity of SPI reflects the true distribution of hydrophobic residues on the protein surface and can be used as an ideal key indicator to assess and predict changes in protein surface activity.This topic provides a new idea and theoretical basis for the subsequent research and application of soy protein modification.