Physicochemical properties and antimicrobial impacts of plasma-activated simulated seawater on Escherichia coli

Background: Some filter-feeding molluscan shellfish can concentrate harmful bacteria in their intestines during feeding, thus posing a potential food safety risk to human consumers. Plasma-activated simulated seawater (PASW) generated from non-thermal plasma may help reduce bacteria in live, molluscan shellfish when used as a disinfectant in depuration systems. This study determined the physicochemical properties of PASW and its antimicrobial efficacy against Escherichia coli DH5 alpha. These results were then compared to similar data from a plasma-activated water (PAW) study. Results: PASW yielded temperatures ranging from 31.00.2 to 49.7 +/- 1.0 degrees C, pH from 7.21 +/- 0.0 to 2.70 +/- 0.0, oxidation-reduction potential (ORP) from -15.7 +/- 1.0 to 246.0 +/- 0.9mV, and electrical conductivity from 35.4 +/- 0.3 to 48.1 +/- 1.5 mu S/cm after activation by plasma for 1-10 min. Temperature, ORP, electrical conductivity, nitrate (NO3-), and nitrite (NO2-) concentrations of PASW increased while pH decreased with increased plasma activation time. After 2- and 5-min incubations, E. coli treated with PASW5 and PASW10 both resulted in the highest reductions (similar to 3 log CFU/ml). Further, while NO3- and NO2- concentrations in PASW were higher than in PAW of the same plasma exposure time, PAW yielded higher E. coli reduction values across treatments. Conclusion: Results from this study demonstrate the potential of PASW as a disinfectant for live, molluscan shellfish depuration to provide a microbiologically safer seafood product for human consumers.