Zein-based asymmetric bilayer film integrated with ligand-regulated metal azolate frameworks for dynamic humidity regulation and Agaricus bisporus preservation

Traditional homogeneous films are often unable to simultaneously maintain a high-humidity microenvironment and buffer relative humidity (RH) fluctuations during fresh-produce storage. Herein, a zein-based asymmetric active packaging film was developed by integrating a ligand-regulated Zein@Metal Azolate Framework 47 (Zein@MAF47) humidity-buffering layer with a dense Zein/humic acid (Zein/HA) barrier layer. MAF47 was grown in situ on electrospun zein fibers through a layer-by-layer assembly strategy, and the 2-methylimidazole/3-methyl-1H-1,2,4-triazole (Hmim/Hmtz) ligand ratio was tuned to regulate water adsorption–desorption behavior. Among the investigated samples, Zein@MAF47 with an Hmim/Hmtz ratio of 3:1 exhibited high-humidity-responsive S-shaped sorption behavior, a water uptake of 0.42 g/g at 90% RH, and stable cycling performance. Meanwhile, the Zein/HA layer formed a compact hydrocolloid network through electrostatic interactions and hydrogen bonding, resulting in a low water vapor permeability of (1.89 ± 0.06) × 10 −11 g·m/(m 2 ·s·Pa). The resulting Zein@MAF47 −Zein/HA bilayer film showed directional water vapor transport and rapidly stabilized the RH at (80 −82)% in a model humidity-regulation system. In preservation experiments, this packaging maintained the internal RH above 97%, thereby reducing the weight loss of Agaricus bisporus to 8.96% under refrigerated conditions and 4.10% at room temperature. These results indicate that coupling a humidity-responsive porous layer with a compact moisture-barrier layer is a promising strategy for developing active packaging films for humidity-stabilized fresh-produce preservation.