Preparation and characterization of covalent starch-protein-tea polyphenol complexes with enhanced interfacial properties.

In this study, covalent octenyl succinic anhydride starch-soy protein- (-)-Epigallocatechin-3-gallate (OSAS-SP-EGCG) complexes were synthesized by HO/ ascorbic acid radical grafting method. Particle size, ζ-potential, Fourier transform infrared, and thermogravimetric results proved the formation of covalent OSAS-SP-EGCG complexes. The results of scanning electron microscopy and atomic force microscopy confirmed that the particles of the covalent complexes (especially 1:4 complexes) were more uniformly distributed. Compared with single OSAS, the covalent complexes exhibited excellent antioxidant capacity (>70 %). Static/dynamic contact angle, dynamic interfacial tension and quartz crystal microbalance were used to characterize the interfacial properties of the samples. Results showed that the stronger hydrophobicity of the complexes resulted in lower interfacial tension, which was stabilized at 17 mN/m after 45 min. Among the complexes, 1:4 complexes showed the most visible interfacial properties, with the initial and equilibrium surface values increasing by 12.1 % and 24.3 %, respectively. Moreover, the saturated f displacement of 1:4 complexes reached 50.45 Hz. It was indicated that better interfacial adsorption capacity of the complexes allowed them to adsorb more quickly to the oil-water interface and form thicker and denser interfacial films. This work provides a promising avenue for improving the interfacial properties of covalent polysaccharide-protein-polyphenol complexes.