Esterification of dextran by octenyl succinic anhydride (OSA): Physicochemical characterization and functional properties assessment

The chemical modification of biopolymers to enhance their functional properties in the food, cosmetic, and pharmaceutical industries is an area of particular interest today. In this study, different molecular weight dextrans were chemically modified for the first time with octenyl succinic anhydride (OSA). This reaction involves an esterification process wherein the hydroxy groups of dextran are partially substituted by a carbonaceous chain, imparting hydrophobic properties to dextran molecules and, consequently, an amphiphilic nature. To assess and quantify the incorporation of OSA into the dextran structure, reaction products were analysed using NMR and FTIR. Additionally, the thermal properties, the Z-potential and the foaming and emulsifying capacity of both native and modified dextrans were examined. The introduction of OSA groups to dextran molecules, with degrees of substitution between 0.028 and 0.058, increased the zeta potential and the thermal stability of the polymer. Furthermore, the chemical modification of dextran backbone with this radical conferred a hydrophobic nature to the biopolymer, which enhance its foaming and emulsifying capacity. Therefore, these results demonstrate that the incorporation of hydrophobic moieties into dextran polymers improves their functional properties and broadens their potential applications in the industry.