Novel Green Synthesis of Octenyl Succinic Anhydride Esters of Granular Starch

Granular starch octenyl succinic anhydride (OSA) esters have most often been prepared in aqueous media, resulting in low reaction efficiencies and degree of substitution. In this study, granular maize and potato starch esters with OSA were synthesized in aqueous ionic liquid (IL) solutions at 35 °C for the first time. The reaction efficiency (RE) of starch esterification and the degree of substitution (DS) of granular OSA-maize starches prepared in a mixture of IL/water of 2:8 (w/w) were increased significantly by 35.3 and 35.6%, respectively. The pasting, textural, and emulsion properties of the OSA-starches were improved greatly. Our results showed that both the DS and the structural changes of starch following esterification determined the functional properties of OSA-starches and that OSA-potato starches presented different functional properties compared with OSA-maize starches. Compared with other mass ratios of IL/water mixtures, the optimum RE and DS for both maize and potato starches were obtained with a 2:8 (w/w) IL/water mixture. The method developed in the present study provides a green and sustainable strategy for starch-OSA modification due to its improved reaction efficiency, reduced usage of IL, and retention of the granular morphology of the derivatized starches.