The improved emulsification properties and enhanced ionic cross-linking capability of octenyl succinic anhydride modified sunflower pectin

Sunflower pectin (SP) is a distinctive type of low-methoxy pectin known for its biological activity and excellent gel-forming properties. However, its emulsifying capacity is relatively limited. To improve the emulsifying performance of SP, this study utilized octenyl succinic anhydride (OSA), a commonly employed modifying agent, to esterify SP. OSA-modified SP samples with varying degrees of substitution (DS) were synthesized. The primary chemical structure of OSA-SP at different DS levels was analyzed using Fourier transform infrared spectroscopy and nuclear magnetic resonance, while conformational changes were assessed through Congo red analysis. The emulsifying properties of OSA-SP were systematically evaluated using Lumisizer, particle size, zeta potential, optical microscopy, and confocal laser scanning microscopy. Solution behaviour and ion-induced gelation capabilities of OSA-SP were investigated through rheological studies. The results demonstrated that the emulsifying performance of OSA-SP improved progressively with increasing DS. Notably, although the viscosity and viscoelasticity of the OSA-SP solution were lower than those of SP, it still retained the gel-inducing ability of K + , Ca 2+ , and Ba 2+ for native SP, and also forms a gel in the presence of Mg 2+ . Furthermore, in vitro cell experiments confirmed that the Mg 2+ crosslinked OSA-SP hydrogel exhibited excellent biocompatibility. This study provides valuable insights into the emulsifying and gel-forming properties of OSA-SP across different DS, thereby supporting its potential application as a thickener, gelling agent, and emulsifier in various fields, including food science, biomedicine, and cosmetics.