Cyclodextrin-based supramolecular deep eutectic solvents modulate curcumin stabilization and the structure-property relationships of potato starch-PVA films

Abstract

Potato starch (PS) films require plasticization, but traditional plasticizers often increase hygroscopicity and water sensitivity. Curcumin, due to its poor solubility and instability, is difficult to incorporate into hydrophilic matrices. Here, curcumin-loaded supramolecular deep eutectic solvents (SUPRADES) based on citric acid and α-, β-, or γ-cyclodextrin were introduced into PS-PVA films as an integrated solubilizing, plasticizing, and functional phase. SUPRADES increased the solubility of curcumin from 0.003 to 4.17 mg/mL, and β-SUP provided the strongest protection against light-induced degradation. FTIR, rheology, and DFT analyses indicated that the stabilization of curcumin originated from its confinement in a supramolecular environment dominated by van der Waals forces and assisted by electrostatic complementarity and hydrogen bonding. After incorporation into PS-PVA, SUP-CUR reorganized intermolecular interactions and matrix packing, enhancing ductility, UV shielding, surface hydrophobicity, and barrier properties without increasing water sensitivity. A clear cavity size-dependent effect was observed: β-SUP favored the stabilization of curcumin, while γ-SUP more effectively translated supramolecular regulation into film properties. PS-PVA-γ60 demonstrated the most balanced performance and extended the shelf life of cherry tomatoes by 6 days. Overall, CD-based SUPRADES offers a cavity size-dependent strategy for stabilizing hydrophobic active substances and regulating starch-based film matrices.