Photocatalytic antimicrobial films mediated by p-coumaric acid-modified chitosan-coated zinc oxide nanoparticles for efficient freshness preservation of strawberries

The problem that strawberries are highly susceptible to microbial infection and have a short shelf life seriously limits their practicality. Therefore, it is imperative to develop advanced packaging films with excellent antimicrobial properties. This study developed a novel encapsulation agent for the synthesis of ultra-low particle size ZnONPs. An antibacterial system of p-coumaric acid -modified chitosan (PCS) coated ZnONPs (ZnONPs@PCS) under blue light photocatalysis was constructed and applied to the PCS and polyvinyl alcohol matrix for strawberry preservation. SEM results indicated that the synthesized ZnONPs@PCS had an average size of 26.10 ± 0.28 nm and exhibited a spherical morphology with good dispersion and outstanding antibacterial performance: the inhibition zone diameters against E. coli and S. aureus were 16.1 mm and 18.5 mm, respectively, with MIC of 300 μg/mL and 150 μg/mL, respectively. ZnONPs@PCS also demonstrated significant photocatalytic activity: exposure to light reduced the absorbance of DPBF by 60.66 %, and the antibacterial performance against E. coli and S. aureus was significantly enhanced compared to dark conditions. The addition of ZnONPs@PCS enables the composite film to exhibit excellent mechanical properties, barrier properties, antibacterial properties, etc. Under light irradiation, the antibacterial efficiency of the PPZ-2 composite film exceeded 95 %, extending the shelf life of strawberries to seven days. This novel composite film holds great promise as an effective packaging material for fruit preservation.