Preparation, water solubility and antioxidant activity of branched-chain chitosan derivatives

Water-solubility at neutral or basic pH of chitosan was largely improved by specific attachment of carbohydrates to the 2-amino functions achieved by Maillard reaction or further reductive alkylation of Schiff bases. The characteristic physicochemical, rheological properties, and antioxidant activities of the derivatives were investigated. Experimental results indicated that the solubility of all the chitosan-saccharides before and after reducing had been greatly enhanced comparing to the native chitosan. The Schiff base typed chitosan–fructose derivative was highest at 13.2 g/L of all, and Schiff base typed chitosan derivatives existed better solubility, Ph stability and more effective scavenging activity against DPPH radical than N-alkylated chitosan derivatives. The degree of substitution (DS) of the chitosan derivatives increased with higher concentration of saccharide, increasing reaction time and temperature. The reduction of viscosity of chitosan derivatives decreased with increasing reaction time and temperature. The results suggest that the water-soluble chitosan derivatives produced through Maillard reaction may be promising commercial additive in cosmetics and food.