Virucidal effect of cold atmospheric gaseous plasma on feline calicivirus, a surrogate for human norovirus

Minimal food-processing methods are not effective against foodborne viruses, such as human norovirus (NV). It is important, therefore, to explore novel nonthermal technologies for decontamination of foods eaten fresh, minimally processed and ready-to-eat foods, and food contact surfaces. We studied the in vitro virucidal activity of cold atmospheric gaseous plasma (CGP) against feline calicivirus (FCV), a surrogate of NV. Factors affecting the virucidal activity of CGP (a socalled radio frequency atmospheric pressure plasma jet) were the plasma generation power, the exposure time and distance, the plasma feed gas mixture, and the virus suspension medium. Exposure to 2.5-W argon (Ar) plasma caused a 5.55 log10 unit reduction in the FCV titer within 120 s. The reduction in the virus titer increased with increasing exposure time and decreasing exposure distance. Of the four plasma gas mixtures studied (Ar, Ar plus 1% O₂, Ar plus 1% dry air, and Ar plus 0.27% water), Ar plus 1% O₂ plasma treatment had the highest virucidal effect: more than 6.0 log₁₀ units of the virus after 15 s of exposure. The lowest virus reduction was observed with Ar plus 0.27% water plasma treatment (5 log₁₀ unit reduction after 120 s). The highest reduction in titer was observed when the virus was suspended in distilled water. Changes in temperature and pH and formation of H₂O₂ were not responsible for the virucidal effect of plasma. The oxidation of viral capsid proteins by plasma-produced reactive oxygen and nitrogen species in the solution was thought to be responsible for the virucidal effect. In conclusion, CGP exhibits virucidal activity in vitro and has the potential to combat viral contamination in foods and on food preparation surfaces.