Enhancing the esterification efficiency and functional properties of octenyl succinic anhydride-modified starch via aqueous-ethanol extrusion pretreatment.

This study first reports that aqueous-ethanol extrusion pretreatment efficiently converts native tapioca starch into V-type starch, greatly enhancing its reactivity for octenyl succinic anhydride (OSA) esterification. Optimized modification of this pretreated starch with only 2% OSA yielded a product (E-OSAS) whose substitution degree and reaction efficiency exceeded those of native starch modified with 3% OSA. E-OSAS exhibited significantly improved hydrophobicity, emulsification capacity, and emulsion stability, forming emulsions with smaller, more homogeneous droplets. These functional characteristics are supported by comprehensive characterization: structural analyses (XRD/NMR) confirmed V-complex formation and successful attachment of OSA groups; DSC indicated complete gelatinization; and other analyses revealed that E-OSAS had larger particle size distribution and displayed characteristic shear-thinning rheology with reduced gel strength. Conclusively, ethanolic extrusion activation significantly enhanced esterification efficiency of starch, offering an efficient and industrially promising ethanol-assisted route for high-RE starch esterification.