Antibacterial and fruit preservation properties of castor oil-based waterborne polyurethane

Waterborne polyurethane (WPU) is a sustainable polymer valued for its mechanical strength, flexibility, and biocompatibility. However, its potential in fruit preservation remains underexplored. In this study, a castor oil-based WPU was synthesized and evaluated for antibacterial activity, preservation performance, and biosafety. The nanoscale WPU emulsion exhibited strong film-forming ability and inhibited Escherichia coli and Staphylococcus aureus by disrupting membranes, as indicated by protein/nucleic acid leakage, elevated superoxide dismutase (SOD) activity, and structural damage. When applied to grapes, cherry tomatoes, blueberries, and bananas, WPU effectively reduced microbial contamination, delayed weight loss, and maintained pH and pigment stability during storage. Biosafety tests showed no adverse effects on wheat seed germination and low cytotoxicity toward eukaryotic cells at moderate concentrations. These results highlight the multifunctional potential of castor oil-based WPU as a safe, bio-based antimicrobial coating for postharvest fruit preservation and an eco-friendly alternative to traditional chemical preservatives.