Fabrication, characterization, and application of catechin-dextran-egg white protein conjugates: Novel antioxidant emulsifiers

The aim of this study was to fabricate dual-function antioxidant emulsifiers using natural ingredients. Catechin-dextran-egg white protein (EC-Dex-EWP) conjugates were prepared using a two-step method: (i) free radical grafting of dextran to EC; (ii) attachment of EC-Dex to EWP using the Maillard reaction. The total phenolic equivalent of the conjugates formed was 4.91 mg EC per gram of conjugate and the free amino content decreased by 19.2% compared to EWP. The formation of EC-Dex-EWP conjugates was confirmed by electrophoresis, infrared spectroscopy, and fluorescence spectroscopy. The interfacial tension of the conjugates was higher than for pure proteins, which was attributed to their larger molecular weight and lower hydrophobicity that EWP. The conjugation of EC-Dex to EWP did not affect the solubility of the protein but it did improve its emulsifying properties. The thermal stability of proteins was improved through Maillard reaction. Moreover, the conjugates also exhibited a stronger antioxidant activity, which was attributed to the presence of polyphenols. Our results suggest that the protein-polysaccharide-polyphenol conjugates developed in this study have potential as novel surface-active antioxidants for improving the physicochemical stability of emulsion-based foods.