Stearic acid-functionalized high amylose starch nanoparticles: Tailoring interfacial wettability and thermal...

High amylose starch nanoparticles (HSNPs) were functionalized with stearic acid (SA) to enhance their efficacy as Pickering emulsion stabilizers. Through ethanol pre-washing, removable and residual SA fractions were differentiated, revealing that removable SA primarily dictates surface hydrophobicity. Specifically, 8% SA loading increased the contact angle from 68° to 80°, indicating enhanced surface hydrophobicity and favoring particle adsorption at the oil-water interface. Emulsions stabilized by HSNP-SA composites exhibited superior stability, with unwashed 8% SA samples achieving a 100% emulsion index. Furthermore, SA incorporation significantly enhanced thermal resistance; while untreated HSNPs showed 15% oiling-off under thermal stress (100 °C for 20 min), the 8% SA variant reduced this to less than 6%. PCA confirmed that interfacial and thermal properties, rather than particle size, predominantly govern emulsion stability. These findings establish that SA localization critically modulates the structure-function relationship of starch nanoparticles, providing a clean-label strategy for developing thermally stable Pickering emulsifiers.