Effect of anionic polysaccharides on conformational changes and antioxidant properties of protein-polyphenol binary covalently-linked complexes

摘要

This work evaluated the anionic polysaccharides to improve the functional properties and antioxidant activities, and compared the effects on covalently-linked the soy protein isolate (SPI)- (-)-epigallocatechin-3-gallat (EGCG) binary complexes. The increasing molecular weight via covalent insertion of ()-epigallocatechin-3-gallat (EGCG) into the soy protein isolate (SPI) was verified by SDS-PAGE. The addition of polysaccharides had no obvious effects on the molecular weight, indicating noncovalent insertion by adsorption. Fourier transform infrared spectroscopy (FT-IR) analysis suggested that SPI-EGCG complexes mixed with polysaccharides changed the secondary structures of SPI with a decrease in alpha-helix and an increase in beta-turn. The emulsions exhibited better stability index (ESI) by adding polysaccharides than the binary complexes emulsion, with decreased particle sizes and increased absolute zeta-potential values, while the value of ESI for the pectin mixed increased more. The 1,1-dipheny1-2-picrylhydrazyl radical (DPPH center dot) scavenging capacity of SPI-EGCG complexes with the addition of polysaccharides were both greater than 70 %. These findings indicated that anionic polysaccharides could be potentially used as a natural and safe alternative for regulating covalently-linked SPI-EGCG emulsion stability and improving emulsion oxidation resistance.