Effect of Salt Ion on the Stability and Interfacial Adsorption Characteristics of Soybean-Whey Mixed Protein Emulsion

In actual production, salt ions were unavoidably present in emulsion-based foods and beverages. Different ion concentrations(0~0.5 mol/L of NaCl) effect on interfacial characteristics of mixed proteins and emulsion stability by particle size, Zeta potential, emulsion stability coefficient, confocal laser scanning microscopy, interface protein adsorption, interface pressure, and interface expansion rheology. The results showed: Salt ions increased the surface potential of mixed proteins emulsion. With the increasing of ion concentration, the volume average particle diameter of the emulsion increased, the emulsion stability coefficient decreased, and the emulsion stability decreased. In addition, the emulsion with a higher salt ion concentration was more unstable than when the salt ion concentration was low. When the salt ion concentration was low(0.05~0.2 mol/L), the emulsion stability coefficient was high, indicating that the emulsion was more stable, especially at 0.05 mol/L, the highest stability coefficient was 97.73%±0.70%. In addition, salt ions weakened the interaction of SPI-WPI at the oil-water interface, resulting in an increasing in the interface pressure value of the SPI-WPI solution. The total modulus(E), elastic modulus(E_d), and viscous modulus(E_v) at the oil-water interface were reduced, which in turn affected the stability of the emulsion. This would provide a theoretical basis for the production of a more stable double-protein emulsion in the food industry.