Effect of oxidative modification on physicochemical and functional properties of soybean polysaccharides

Abstract

Oxidized soybean polysaccharides (OSSPS-1 and OSSPS-2) were prepared. Their structure was characterized, and their physicochemical and functional properties were evaluated. Structural analysis showed that the hydroxyl groups of soybean polysaccharides (SSPS) were oxidized to carboxyl groups. The molecular weight decreased from 1.5 × 105 Da (SSPS) to 7.2 × 104 Da (OSSPS-1) and 7.0 × 104 Da (OSSPS-2), respectively. The carboxyl content of SSPS, OSSPS-1 and OSSPS-2 was 1.79%, 6.08% and 9.45%, respectively. Uronic acid content of SSPS, OSSPS-1 and OSSPS-2 was 4.15%, 7.39% and 10.29%, respectively. Compared with SSPS, OSSPS-1 and OSSPS-2 showed decreased emulsifying property. Oxidative modification greatly reduced the viscosity of SSPS and changed their viscoelasticity. Whereas, oxidative modification improved a series of viscosity-related functional properties of SSPS, such as fat binding capacity, bile acid binding capacity, hypoglycemic effect. The antioxidant and antibacterial activities of SSPS were enhanced after oxidative modification. OSSPS-1 possessed higher DPPH scavenging ability, ferrous iron chelating ability and reducing power than OSSPS-2, but OSSPS-2 showed better antibacterial activities than OSSPS-1. The result revealed that oxidative modification had a significant effect on the structure of SSPS, which further affected the functional properties and biological activities of SSPS.