Construction of bilayer asymmetric humidity-regulating packaging using 2-hydroxypropyl trimethyl ammonium chloride...

To ensure high-quality harvested fruits and vegetables, maintaining a stable, high relative humidity is crucial. This study concentrated on the development of an asymmetric double-layer film designed to address the limitations inherent in single-layer films. The film incorporates 2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC) as an autonomous humidity control material. HACC has a water adsorption energy of -2.03 eV, higher than polyvinyl alcohol (PVA), indicating better water absorption. The PVA/HACC film evenly distributes water molecules and has a higher adsorption capacity. HACC enhances adsorption kinetics and equilibrium through a synergistic "hydrogen bond-electrostatic" mechanism and increased free volume. Increasing the HACC concentration to 1.0% elevates the active layer's water absorption capacity to 0.43 g/g. The double-layer film exhibits a remarkably low water vapor permeability of (1.66 ± 0.03) × 10^-11 g·m/(m²·s·Pa), effectively minimizing moisture exchange. When used for fresh strawberries, compared with the control group, it increased internal relative humidity by 126.54% and reduced the relative humidity variation to 1.62 × 10^-2, effectively extending freshness to 7 days at room temperature. This innovative packaging solution actively regulates humidity, prolonging the freshness of fruits and vegetables. To encourage practical use, it's essential to assess the main challenges of large-scale promotion.