Characterization and mechanism of ferulic acid/γ-cyclodextrin inclusion complex: Stoichiometric optimization and application in active food packaging films.

Ferulic acid (FA) exhibits strong bioactivity but is limited by poor aqueous solubility and photostability. To address these limitations, this study evaluated the physicochemical properties of FA/γ-cyclodextrin (γ-CD) inclusion complexes prepared at varying molar ratios (1:1, 1:2, and 2:1). Structural characterizations confirmed successful encapsulation through crystalline phase transformations and morphological changes. Among the tested formulations, the 1:2 complex achieved the highest encapsulation efficiency (79.74%), while the 2:1 complex maximized loading efficiency (20.45%) and solubility (5.9-fold enhancement). The 1:1 complex exhibited enhanced photoprotection during the early stage of storage (92.3% retention over 4 days) and the highest in vitro intestinal bioaccessibility (86%). To further understand the underlying mechanism, molecular dynamics simulations were conducted, revealing that the stability of the 1:1 complex is mainly driven by van der Waals interactions, with additional contributions from hydrogen bonding. Furthermore, active packaging films were developed by incorporating the 1:1 complex (6 mg) into a hydroxypropyl methylcellulose matrix, and they showed good UV-blocking performance and mechanical properties. Application in fresh-cut apples revealed that the films effectively reduced enzymatic browning and maintained firmness during a 5-day storage period. This study offers new insights into molar ratio-dependent CD complexation and provides guidance for the design of active food packaging systems.