Adlay seed starch modified with octenyl succinic anhydride interacting with quercetin: Interaction mechanism and...

Octenyl succinic anhydride (OSA) starch is a prominent particle stabilizer for Pickering emulsions, yet it often fails to protect polyunsaturated lipids effectively due to its lack of intrinsic antioxidant activity and the uneven distribution of interfacial hydrophobic groups. We hypothesized that quercetin's (QR) hydrophobic nature would allow it to assemble with OSA-modified adlay seed starch (OSA-ASS), thereby improving emulsifying properties and providing antioxidant capacity. To verify this hypothesis, we prepared OSA-ASS/QR complexes containing 0.5%-3.5% QR to stabilize walnut oil emulsions. The interaction mechanisms were elucidated via fluorescence spectroscopy, isothermal titration calorimetry (ITC), and molecular dynamics (MD) simulations. The results revealed that QR spontaneously bound to OSA-ASS, an entropy-driven process dominated by hydrophobic interactions, while hydrogen bonding and van der Waals forces provided structural specificity and supplementary enthalpic stabilization. The 2.5% QR complex facilitated the formation of a compact interfacial barrier that restricted water mobility. Ultimately, the system achieved dual protection: the dense physical barrier hindered pro-oxidant permeation, while interfacial QR chemically scavenged free radicals. These findings clarify the entropy-driven assembly of starch-polyphenol complexes, offering a robust strategy for encapsulating unsaturated oils.