Multifunctional curcumin-loaded soybean oil-based waterborne polyurethane films with the outstanding barrier, antioxidant and antibacterial properties for active fruit packaging

Bio-based waterborne polyurethane (WPU) films have attracted much attention to replacing plastic films in food packaging fields. Despite recent clear progress in constructing bio-based WPU films, it is still a challenge to fulfill suitable mechanical property, high water and gas-resistant behavior, outstanding UV-blocking performance, favourable antioxidant and antibacterial activities at the same time in a bio-based WPU film. Herein, curcumin (Cur)-loaded soybean oil-derived WPU multifunctional films are developed by an in-situ emulsion encapsulation method. The results indicate that Cur is homogeneously embedded in WPU film matrix, and interacts with WPU chain through hydrogen bonds to compactify film structure. And the incorporation of Cur can significantly enhance the overall performances of WPU films. The optimal WPU film displays favourable mechanical property with the tensile strength of 10.95 MPa and strain at break of 1511.02 %, high water barrier performance with water contact angle of 100.9° and water vapor permeability rate of 0.77 × 10 −10 g·m −1 ·s −1 ·Pa −1 , favorable gas barrier behavior with the oxygen and carbon dioxide permeabilities of 1.24 × 10 −10 g·m⁻¹ ·s⁻¹ ·Pa⁻¹ and 2.49 × 10 −10 g·m⁻¹ ·s⁻¹ ·Pa⁻¹ , and the nearly complete UV-blocking capability. Furthermore, the optimal WPU film demonstrates remarkable antioxidant activity with ABTS radical scavenging rate as high as 98.02 %, clear antibacterial ability with the inhibition rates of 89.35 % against E. coli and 98.33 % against S. aureus . Interestingly, the results of litchi preservation tests imply that Cur-loaded WPU films effectively delay litchis deterioration and extend litchis shelf life. This study provides a robust strategy for designing high-performance, bio-based active packaging films for fruit preservation application fields.