Eggshell-inspired heterogeneous bilayer paper window with selective gas permeability for preserving fresh produce

Abstract

To prevent the increasing waste of fresh produce, there is a need for low-cost, easy-to-manufacture, and sustainable preservation packaging. Here, inspired by an “eggshell” that protects the life inside, a novel and simple packaging system called the “paper window”, has been developed for fresh produce preservation. It employs nanochitin/poly (ethylene glycol) as the “inner membrane”, on a base paper surface, with the base paper serving as the “outer shell”, to regulate O₂ and CO₂ permeability as well as CO₂/O₂ selective permeability. Molecular dynamics simulation shows that the paper window exhibits a stable bilayer structure with negative surface interaction energy. It also confirms that the nanochitin/poly (ethylene glycol) coating forms a stronger adsorption capacity for CO₂ than O₂, resulting in a CO₂/O₂ selective permeability of 1.65–3.71 with gas permeability ranging from 2000 to 14000 cm³‧m⁻²‧d⁻¹‧0.1 MPa⁻¹. The mechanical characteristics, water vapor permeability, and water contact angle of the paper window facilitate its usage, transportation, and storage. The paper window has been validated in preserving litchi, demonstrating better sensory value and chemical properties compared to those stored in air or polyethylene at 25 ± 3°C for 8 d. The paper window shows promising potential for large-scale production and application in the preservation of various fresh produce.