Preparation of Polylactic Acid/Chitosan/Cinnamaldehyde One-Way Moisture Barrier Bilayer Film and Its Application in the Preservation of Pleurotus geesteranus

Pleurotus geesteranus, being rich in nutrients and moisture, easily loses water and wilts after harvest, reducing its commercial value. Furthermore, film packaging leads to excessive humidity in the internal environment, causing products to decay. In this study, polylactic acid (PLA) and chitosan (CS) were used as film-forming substrates to prepare a one-way moisture barrier bilayer film containing 0.25% cinnamaldehyde nano-emulsion (CANE). The microstructure, physical properties, optical properties, mechanical properties, moisture barrier properties and sustained release behavior of the film were investigated and its application in the preservation of P. geesteranus was evaluated. The results showed that the combination between PLA and CS could effectively make up for the defects of the monomer film, and the layers in the composite film with 0.25% CANE were tightly bound to each other, with a retention rate of 42% for cinnamaldehyde (CA). The film had strong ultraviolet resistance and the smallest settling speed of water droplets. The P layer had good water vapor barrier properties, and the C layer had good hydrophilicity. Compared with polyethylene (PE) film packaging, the 0.25% CANE-PLA-CS bilayer film significantly inhibited the browning and respiratory intensity of P. geesteranus during postharvest storage, delayed the increase in mass loss, soluble solids content, browning degree, electrical conductivity and malondialdehyde (MDA) content, reduced the activities of polyphenol oxidase (PPO) and peroxidase (POD) and maintained higher superoxide dismutase (SOD) activity. These results indicated that the one-way moisture barrier bilayer film could effectively delay the browning and aging of P. geesteranus and maintain its commercial value. This study provides theoretical support for the preparation of novel packaging materials for mushrooms and is of guiding significance to the reduction of post-harvest loss of P. geesteranus.