Lotus leaf flavonoid-loaded zein/chitosan composite films for controlled-release active food packaging

Lotus leaf flavonoids (LLF), derived from an abundant agricultural byproduct, were incorporated into zein/chitosan (ZC) matrices to fabricate multifunctional edible films with controlled-release properties for active food packaging applications. LLF-ZC composite films containing different flavonoid loadings (0.1-0.3%, w/v) were prepared and systematically evaluated in terms of physicochemical, mechanical, thermal, structural, and bioactive properties. The incorporation of LLF significantly increased film thickness, density, tensile strength, and thermal stability, while maintaining low water vapor and gas permeability. Structural characterization by SEM, ATR-FTIR, and XRD confirmed good compatibility between LLF and the ZC matrix, mainly attributed to hydrogen bonding and hydrophobic interactions. LLF addition markedly enhanced the antioxidant and antibacterial performance of the films, with DPPH and ABTS radical scavenging activities exceeding 90% at higher LLF contents and concentration-dependent inhibition against Escherichia coli and Staphylococcus aureus. Among the tested formulations, the 0.2% LLF-ZC film exhibited the most balanced overall performance in terms of mechanical strength, barrier properties, and bioactivity. The release behavior of LLF was strongly influenced by the polarity of food simulants, with the highest cumulative release observed in 50% ethanol, followed by water and 95% ethanol. Kinetic analysis indicated that the release profiles were best described by the Peppas-Sahlin and Ritger-Peppas models, demonstrating that Fickian diffusion was the dominant release mechanism. Overall, these results highlight the potential of LLF-ZC films as sustainable active packaging materials, particularly for semi-fatty food systems.