pH-induced conformational changes and interfacial dilatational rheology of soy protein isolated/soy hull polysaccharide complex and its effects on emulsion stabilization

In this study, the effects of conformational conversion and interfacial dilatational rheology of soy protein isolated (SPI)/soy hull polysaccharide (SHP) on physical stability of oil-in-water (O/W) emulsions were investigated at pH 3.0–9.0. The results showed that SHP enhanced the physico-chemical stability of SPI emulsions at pH 3.0–9.0. At pH 5.0, SPI/SHP emulsions that have a smaller particle size, interfacial tension, and a higher electrostatic repulsion was developed. FTIR and Raman spectroscopy indicated that the secondary structures of the α-helix and random coil of SPI/SHP complexes changed with pH. SHP decreased the interaction between proteins adsorbed at the oil-water interface and the SPI/SHP complex presented a stronger interaction at pH 5.0. The electrostatic, hydrophobic, and hydrogen bonding interactions played an essential role in the polar or hydrophobic environment of the tryptophan and tyrosine residues inside protein molecules. These findings indicated that the SPI/SHP complex shows potential for commercial application in the production of novel functional emulsions.