Antimicrobial effect of plasma-activated water combined with tartaric acid against Staphylococcus aureus and its application on fresh-cut asparagus lettuce

Abstract

Plasma-activated water (PAW) is increasingly recognized for its role in mitigating microbial contamination in fresh-cut produce, but its disinfection effectiveness can be limited under certain conditions. Notably, dissolving organic acids in PAW is an effective way to boost its antimicrobial properties through a synergistic effect. This study examined the enhanced antimicrobial efficacy of PAW when combined with tartaric acid against Staphylococcus aureus and its application on fresh-cut asparagus lettuce. Results demonstrated that PAW combined with tartaric acid showed stronger antimicrobial efficacy than PAW alone (p < 0.05). The addition of tartaric acid to PAW increased the oxidation-reduction potential and lowered the pH, contributing to its superior antimicrobial performance against S. aureus. The underlying antimicrobial mechanisms included the inactivation of Ca2+-Mg2+-ATPase and Na+-K+-ATPase accompanied by damage to bacterial cell membrane, enhanced oxidative damage due to the influx of extracellular reactive oxygen species such as H2O2, the disrupted energy metabolic activities, and the mitigated bacterial defense system constructed by antioxidant enzymes, such as superoxide dismutase and catalase. Furthermore, the synergistic treatment improved the quality of fresh-cut asparagus lettuce by retarding browning, curbing microbial spoilage, and lessening weight loss. The preservation of color was largely due to the decreased activities of polyphenol oxidase and peroxidase, along with controlled chlorophyll degradation. These findings suggest that PAW enhanced with tartaric acid could be a promising, cost-effective disinfection strategy for fresh-cut asparagus lettuce.