Carboxymethyl chitosan-based multifunctional films combined with tea polyphenols and copper oxide nanoparticles for...

Biodegradable food packaging films with bioactive properties are urgently needed to address food safety and quality challenges. This study aims to leverage the synergistic effects of varying concentrations of tea polyphenols (TP) and copper oxide nanoparticles (CuO NPs) to develop multifunctional carboxymethyl chitosan (CMCS)-based biodegradable composite films for cherry tomato preservation. The developed films were characterized via SEM, XRD, and FTIR analyses, and their physical, mechanical, UV-blocking, antioxidant, and antimicrobial properties were thoroughly evaluated. Results demonstrated that compared with the control, the CMCS film containing 0.5 wt% TP and 0.2 % w/v CuO NPs presented significantly enhanced hydrophobicity (62 % reduction in water solubility), tensile strength (61.51 %), and UV-blocking properties (>99 %), a marked increase in antioxidant activity (63.33 ± 0.71 % relative to 4.87 ± 0.76 % in the pure CMCS), and potent bactericidal effects against Staphylococcus aureus and Escherichia coli, resulting in a 6-log reduction in bacterial viability within 12 h. The synergistic antibacterial mechanisms were attributed to the combined action of reactive oxygen species (ROS) generated by the CuO NPs and the membrane disruption effects of the TP/CuO NPs. The films demonstrated favorable biodegradability, with a degradation rate of 60.28 % ± 3.11 after 7 days, and when applied as food packaging for cherry tomatoes, the films significantly extended shelf-life by more than 15 days, minimizing weight loss, maintaining firmness, reducing decay rates, and preserving overall freshness during storage. These findings establish CMCS/TP/CuO NPs films as innovative, eco-friendly, and multifunctional packaging for diverse food packaging applications.