Resveratrol mediated photodynamic inactivation using UVA light on foodborne pathogens

Non-thermal strategies for microbial inactivation are increasingly explored to overcome the drawbacks of conventional thermal processing. In this study, resveratrol, a natural polyphenol with well-documented antioxidant properties, was examined as a food-compatible photosensitizer to improve the antimicrobial efficacy of UVA-driven photodynamic inactivation (PDI). Three representative foodborne pathogens, Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes, were used as target microorganisms. At a dose of 10 J/cm², 365 nm UVA combined with 100 μM resveratrol achieved more than 5 log CFU/ml reductions of pathogens, which were significantly (P < 0.05) higher than either treatment alone. No comparable enhancement was observed at 385 or 405 nm, indicating wavelength-dependent photoactivation of resveratrol. This synergistic effect was more pronounced in L. monocytogenes than in E. coli O157:H7 and S. Typhimurium, likely due to its higher inherent resistance to UV exposure. Mechanistic analysis identified hydroxyl radical (•OH) and singlet oxygen (¹O₂) as the major ROS responsible for bacterial inactivation, whereas hydrogen peroxide (H₂O₂) and superoxide anion (O₂^•-) played only minor roles. The combined treatment induced significant membrane damage, intracellular ROS accumulation, and lipid peroxidation, indicating that oxidative stress is the primary mechanism of microbial inactivation. In evaluating the potential in food applications using apple juice, resveratrol-mediated PDI achieved a microbial reduction of nearly 5 log CFU/ml without affecting essential quality attributes, including color, pH, and antioxidant activity. These results demonstrate the potential of resveratrol as a natural, effective, and non-toxic photosensitizer for liquid food applications.