The addition of phenolic acids contributes to the regulation of protein phase aggregation behavior: The enhancement of polysaccharide complexation and the improvement of environmental conditions of bilayer emulsions.

To overcome the limited electrostatic interaction between soy protein isolate (SPI) and chitosan (CS) around pH 4.5-6.5, phenolic acids (chlorogenic acid CA and rosmarinic acid RA) were added to adjust the isoelectric point of SPI which increase the electrostatic force and enlarge the pH range of interaction with CS. Spectral analysis showed that CA/RA was conducive to unfolding the protein structure and improving the protein emulsifying and antioxidant characteristics. The bilayer emulsions were prepared by SPI-CA / SPI-RA as inner emulsifier and CS as outer emulsifier. It showed that the addition of CA/RA reduced the emulsions particle sizes, and caused higher absolute Zeta potential values and thicker droplet boundary membrane. Thus, SPI-CA-CS / SPI-RA-CS bilayer emulsions showed better emulsion storage, oxidation, and thermal stability under weak acid conditions. This paper provides a theoretical basis for developing a safe and stable bilayer emulsion delivery system -stabilized by protein-polyphenol complex and chitosan.