Structure and Antioxidant Activity of Soy Protein Isolate-Dextran Conjugates Obtained by TiOPhotocatalysis

Abstract

The aim of this study was to investigate the structural characteristics and antioxidant activities of soy protein isolate- (SPI-) dextran conjugates obtained by TiOphotocatalysis treatment. Results revealed that the UV-vis absorption and the fluorescence intensity increased as the photocatalytic power increased (P < 0.05). Higher photocatalytic power could promote the extent of glycation and the formation of high molecular weight SPI-dextran conjugates, which were evidenced by free amino group content and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The Fourier transform infrared (FT-IR) spectra suggested that the amide I, II, and III bands of SPI were altered by the glycation induced by TiOphotocatalysis. Moreover, significant changes of secondary structure occurred in SPI-dextran conjugates. The -helix, β-sheet, β-turns, and random coil were changed from approximately 10.6%, 37.9%, 12.9%, and 38.6% to 3.8%, 10.4%, 17.7%, and 68.8%, respectively, after treatment at photocatalytic power of 1000 W. In addition, SPI-dextran conjugates obtained by TiOphotocatalysis treatment exhibited high hydroxyl radical scavenging activity and possessed increased reducing power. All data indicated that TiOphotocatalysis was an efficient method for promoting protein-polysaccharide copolymerisation.