Mechanistic Insights into Starch-Polyphenol Complexation: Role of Structural Differences in Galloyl-Based Polyphenols

Fruit and vegetable processing by-products, such as peels and pomace, are rich in antioxidant polyphenols and represent promising sources of functional ingredients, but how their galloyl-based polyphenols interact with starch remains insufficiently understood. In this study, corilagin with three non-free galloyl moieties and 1,2,3,4,6-O-pentagalloyl glucose with five free galloyl moieties were used as model polyphenols to clarify how galloyl moiety number and accessibility modulate their complexation with high-amylose maize starch (HAMS). Size-exclusion chromatography showed that both polyphenols preferentially complexed with amylose, while FTIR confirmed that complex formation occurred mainly through non-covalent interactions. The two polyphenols induced distinct changes in HAMS structure. Corilagin disrupted short-range order and produced no detectable crystalline structure, whereas 1,2,3,4,6-O-pentagalloyl glucose enhanced molecular order and induced V-type crystallization. Isothermal titration calorimetry revealed more binding sites but weaker affinity for corilagin, with thermodynamic signatures indicating hydrogen bonding and van der Waals interactions. By contrast, 1,2,3,4,6-O-pentagalloyl glucose showed stronger affinity and hydrophobic interaction-dominated binding. Molecular dynamics simulations further confirmed that 1,2,3,4,6-O-pentagalloyl glucose formed a more stable association with the amylose helix than corilagin. These results indicate that galloyl moiety characteristics markedly influence starch–polyphenol interaction mechanisms, providing guidance for the utilization of polyphenol-rich agro-processing by-products in functional starch-based foods.