Development of multifunctional and sustainable starch/polyvinyl alcohol–polyethylene glycol copolymer films reinforced with green tea extract for food packaging

Abstract

This study explores a sustainable alternative to conventional plastic packaging by developing biodegradable films from starch (ST), a polyvinyl alcohol–polyethylene glycol (PVA–PEG) copolymer and green tea extract (TE) as a functional additive. The incorporation of TE at 0.5% w/v was demonstrated to significantly enhance the tensile strength (4.7 ± 0.3 MPa) and water contact angle (70.7 ± 0.3°) of STKTE 0.5% film in comparison to a blank STKB film. The developed films also demonstrated significant improvement in barrier attributes, including UV-shielding (100%), water vapour and oxygen transmission. Further, the films were analysed using several techniques, including scanning electron microscopy (SEM), 3D optical profilometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results demonstrated that incorporating TE improved the structure, intermolecular interactions and thermal stability of the film. DPPH assay and cytocompatibility (95%) with L929 fibroblast cells confirmed the strong antioxidant properties and biocompatibility of the developed film, respectively. The incorporation of TE enhanced the antibacterial potential of the films, with significant inhibition of Escherichia coli and Staphylococcus aureus. The application of the developed films in the preservation of fresh cut apple cubes demonstrated reduced browning index, weight loss and pH, indicating better preservation compared to the blank film. Finally, the biodegradability of the film was assessed using soil burial tests, demonstrating a residual area of 0.6 ± 0.6% within 10 days. These results highlight the potential of ST/PVA-PEG/TE films as eco-friendly, functional packaging materials to improve food shelf life while ensuring safety and sustainability.