Multifunctional silver/ε-polylysine/diethyl ferulate composite films with improved anti-UV and antibacterial properties for food packaging

Food spoilage is a major challenge to food safety. The development of multifunctional food packaging materials offers an innovative and effective strategy to mitigate this issue. In this study, we successfully synthesized the water-soluble Silver - polylysine - diethyl ferulate (Ag-PLL-DEF) polymer using a CuAAC reaction and an in situ growth method, which enhanced the dispersibility of diethyl ferulate (DEF) in aqueous solutions. This polymer was then blended with Polyvinyl alcohol (PVA) to create the Ag-PLL-DEF/PVA composite film. Our results demonstrate that incorporating DEF significantly improved the UV resistance of the composite film, with the UV shield rate of the 0.8 wt% Ag-PLL-DEF/PVA composite film reaching 98.62 %. After 30 days of continuous UV irradiation, the composite film exhibited outstanding light stability. The incorporation of Ag and PLL conferred remarkable antibacterial properties to the composite film. The inhibitory zone diameters of the 0.8 wt% Ag-PLL-DEF/PVA composite film against E. coli and S. aureus were 3.3 ± 0.2 mm and 2.75 ± 0.15 mm, respectively. Furthermore, a strawberry preservation experiment confirmed that the Ag-PLL-DEF/PVA composite film effectively inhibited bacterial growth and extended the shelf life of strawberries by up to 7 days. Similarly, preservation experiments with milk and jujube revealed that the composite films reduced photooxidation and significantly prolonged shelf life. This work provides valuable insights into the development of composite films with both anti-ultraviolet and antibacterial properties. It also offers a promising framework for advancing active food packaging technologies.