Design and Functional Characterisation of Bio-Based Multilayer Polylactic Acid Films Incorporating Chitosan and Propolis for Antimicrobial Food Packaging Applications

Abstract

: The development of renewable and bio-based materials with functional performance comparable to conventional plastics remains a key challenge in sustainable packaging. In this study, bio-based multilayer films were fabricated using polylactic acid (PLA) as a renewable polyester substrate, combined with chitosan (CS) and propolis (PRP) as naturally derived functional layers. Sequential surface coating enabled the formation of multilayer architectures integrating complementary structural and antimicrobial properties from bio-derived constituents. Trilayer PLA/CS/PRP films exhibited significantly increased thickness and opacity compared with neat PLA, along with higher ( p < 0.05) water vapour permeability. Mechanical analysis showed significant reductions ( p < 0.05) in tensile strength and elongation at break, reflecting interfacial and structural effects associated with multilayer integration. The preservation performance of the multilayer films was evaluated using fresh mozzarella cheese stored at 4 ○ C for 25 days. Compared with neat PLA, the multilayer films more effectively suppressed the growth of total aerobic bacteria, yeast, and mould during refrigerated storage of mozzarella cheese. Although direct antimicrobial activity of the films was not evaluated, the multilayer system demonstrated improved preservation performance by maintaining pH stability, reducing weight loss, and delaying microbial proliferation. These findings suggest the potential of multilayer bio-based coating strategies for active packaging applications in perishable food products.