Rapid inactivation of multidrug-resistant Salmonella enterica on foods by visible light–activated photocatalytic films

Salmonella enterica is a major cause of global foodborne illness. The emergence of multidrug-resistant (MDR) strains that makes infections harder to treat underscores the urgent need for alternative approaches beyond conventional antimicrobial treatments to reduce MDR Salmonella contamination in foods. In this study, we developed and evaluated a novel antibacterial packaging system by incorporating photocatalytic conjugates into cellulose-based films to inactivate a model MDR strain of S. enterica ser. Typhimurium on foods through the generation of reactive oxygen species (ROS) under visible light. Results showed that TcPP-TiO₂ (Tetrakis (4-carboxyphenyl) porphyrin)-Titanium dioxide (TcPP-TiO₂) conjugates expanded the responsive light wavelength of TiO₂ from the UV to the visible spectrum. Electron paramagnetic resonance (EPR) analysis revealed that higher light intensity promoted ROS production. ROS generated by the film caused a 1.8-log CFU/mL reduction in S. Typhimurium in buffer under low-intensity light (1000 lux) over 96 h. Its antibacterial efficacy increased significantly as the light intensity increased. Under 6000-lux light illumination, the film caused a 4.2-log CFU/mL reduction in S. Typhimurium in the buffer after 72 h. Furthermore, when applied to inoculated mango slices, the film led to a 3-log CFU/mL reduction in S. Typhimurium under light exposure. However, its antimicrobial effect was not significant when applied to inoculated chicken breast, potentially due to ROS scavenging by complex compounds present in chicken breast.