A novel sterilization mechanism of cold plasma coupled with low-dose ZnO nanoparticles for food Decontamination: Synergistic reactive species generation and zinc ion release

Abstract

Zinc oxide nanoparticles (ZnO NPs) have emerged as novel eco-friendly method for food sterilization. However, the usage of high-concentration ZnO NPs exhibit biological toxicity. To overcome the challenge, this study proposed the dual sterilization strategy coupling cold atmospheric plasma (CAP) with hydrophilic ZnO (H-ZnO) NPs for food decontamination to reduce ZnO NPs potential risk and investigated the synergistic sterilization effects and mechanism of CAP coupled with H-ZnO NPs at different concentration (0.001, 0.01, and 0.1 g/L). Results show that the combined treatment can efficiently inactivate Gram-negative (E. coli and S. enterica) and Gram-positive bacteria (L.monocytogenes and S. aureus) on the surface of blueberries. CAP +0.01 g/L H-ZnO NPs had the most obvious synergistic sterilization, and the bacterial reduction was increased by 0.5 log at least among the four strains. The combined treatment of CAP and 0.01 g/L H-ZnO NPs led to the enhanced generation of reactive oxygen and nitrogen species (RONS) and Zn²⁺ release from H-ZnO NPs in the solution. Meanwhile, the released Zn²⁺ flowed into the cell and accordingly increased the intracellular ROS level (670 %), consequently resulting in the improved bacterial inactivation. The low concentration of H-ZnO NPs (0.001 g/L) could not effectively cause membrane potential depolarization, and thus leading to a poor result of coupled sterilization. The high concentration of H-ZnO NPs (0.1 g/L) attaching on S. aureus cell surface may obstruct the interaction between CAP and S. aureus, which showed the worst synergistic bactericidal efficiency. This study proposed CAP/ZnO synergy offers a scalable, low-chemical alternative to conventional decontamination methods, which will address the emerging challenges in food management.