Preparation of starch–sodium lignosulfonate graft copolymers via laccase catalysis and characterization of antioxidant activity

Graft copolymers of waxy maize starch and sodium lignosulfonate (SLS) were prepared by Trametes versicolor laccase catalysis in aqueous solution. Amount of SLS grafted based on phenol analysis was 0.5% and 1.0% in the absence and presence of 1-hydroxybenzotriazole (HBT), respectively. Starch–SLS graft copolymers were effective antioxidants as judged by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. The presence of laccase caused a reduction in starch molecular weight although a cross-linked gel fraction was also observed when HBT was present. This new method for preparing starch chemically modified with phenolic compounds is simple and the resulting antioxidant polymers have potential in food, cosmetic and packaging applications.