Development and functional evaluation of sustainable secalin–polyvinyl alcohol films reinforced by citric acid cross-linking

This study presents the preparation of a composite film based on polyvinyl alcohol (PVA) and secalin (SCL). Citric acid (CA), as a cross-linker, was utilized to chemically modify the composite films. In the preparation of composite and cross-linked films, glycerol was used as a plasticizer, and the casting method was employed. Various properties of the prepared films, including mechanical and barrier properties, were studied. The results showed that blending PVA with SCL improved the mechanical properties of SCL films. Additionally, the barrier properties of the composite films against water vapor and oxygen gas were enhanced compared to pure PVA. Moreover, the modified composite films with the cross-linker not only improved mechanical, barrier, and hydrophobic properties but also introduced antioxidant and antibacterial functionalities. Field emission scanning electron microscopy (FE-SEM) showed that the components used in film preparation had good compatibility. Furthermore, the interaction of CA as a cross-linker with the polymers was confirmed by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra, which revealed shifts in the positions of certain bands. The prepared films were applied for strawberry packaging, demonstrating their potential in extending shelf life and reducing postharvest losses. These properties demonstrate the potential application of the prepared cross-linked film as an active packaging material for preserving food products. • Biopolymer-based films offer eco-friendly alternatives to conventional food packaging. • Biodegradable cross-linkers improve properties of biopolymer-based packaging films. • Citric acid improved PVA/SCL films in barrier, antioxidant, and antibacterial traits. • Cross-linked films showed good PVA, SCL, and CA compatibility in structure and properties. • Cross-linking with CA enhanced the hydrophobicity and mechanical strength of the films.