Optimizing banana preservation with bandgap-dependent curcumin-modified Cu-doped-ZnO nanoparticles in chitosan edible coatings

ZnO nanoparticles possess antimicrobial properties and are widely used in food packaging to enhance food safety and shelf life. This study aimed to synthesize and characterize novel Cu-doped ZnO nanoparticles (Cu-ZnO) further modified with curcumin (Cu-ZnO@cur) to improve antibacterial activity by lowering band gap energy. The efficacy of these nanoparticles was evaluated as an active ingredient in chitosan-based edible coatings for banana preservation. The materials were characterized using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, UV–visible diffuse reflectance spectroscopy (UV-visible DRS), and Transmission Electron Microscopy (TEM). Antibacterial activity was tested against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using the disc diffusion method. The nanoparticles were then incorporated into a chitosan-based matrix and applied as an edible coating for bananas. Cu3%-ZnO and Cu1%-ZnO@cur nanoparticles exhibited the most potent antibacterial activity, with inhibition zones of 13.67 mm and 9.45 mm (against Staphylococcus aureus) and 11.83 mm and 12.89 mm (against E. coli), respectively. Chitosan coatings containing 1% (w/w) Cu3%-ZnO and Cu%-ZnO@cur significantly reduced banana mass loss by 16.42% and 17.58% after seven days of storage. Our findings highlight their potential as effective, eco-friendly antimicrobial agents for enhancing the shelf life of fresh produce and advancing sustainable food packaging solutions.