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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 log 10 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% O 2 , Ar plus 1% dry air, and Ar plus 0.27% water), Ar plus 1% O 2 plasma treatment had the highest virucidal effect: more than 6.0 log 10 units of the virus after 15 s of exposure. The lowest virus reduction was observed with Ar plus 0.27% water plasma treatment (5 log 10 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 H 2 O 2 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. Foodborne illnesses continue to plague public health, as well as world economies, costing approximately $152 billion in the United States alone (1). Enteric viruses, particularly human norovirus (NV) and hepatitis A virus (HAV), are the leading causes of viral foodborne illnesses (2). Human NV, one of the top five pathogens with respect to the total cost of foodborne illnesses in the United States, belongs to the family Caliciviridae and is a wellknown cause of "winter vomiting disease" or "stomach flu" (3). NV causes 19 to 21 million cases of acute gastroenteritis annually in the United States and leads to 1.7 to 1.9 million outpatient visits, 400,000 emergency room visits, 56,000 to 71,000 hospitalizations, and 570 to 800 deaths, mostly among young children (4). More than half of all foodborne disease outbreaks due to a known cause reported to the CDC from 2006 to 2010 were attributed to NV. In the European Union in 2007, caliciviruses (primarily NV) were responsible for 507 of 675 foodborne viral disease outbreaks (5).Multiple issues related to the quality of thermally processed foods, e.g., nutritional losses and adverse effects on organoleptic quality, have led to the emergence of so-called nonthermal technologies, which consist of preservation treatments that are effective at ambient o...

Possible mechanisms that lead to inactivation of feline calicivirus (FCV) by cold atmospheric-pressure plasma (CAP) generated in 99% argon-1% O2 admixture were studied. We evaluated the impact of CAP exposure on the FCV viral capsid protein and RNA employing several cultural, molecular, proteomic and morphologic characteristics techniques. In the case of long exposure (2 min) to CAP, the reactive species of CAP strongly oxidized the major domains of the viral capsid protein (VP1) leading to disintegration of a majority of viral capsids. In the case of short exposure (15 s), some of the virus particles retained their capsid structure undamaged but failed to infect the host cells in vitro. In the latter virus particles, CAP exposure led to the oxidation of specific amino acids located in functional peptide residues in the P2 subdomain of the protrusion (P) domain, the dimeric interface region of VP1 dimers, and the movable hinge region linking the S and P domains. These regions of the capsid are known to play an essential role in the attachment and entry of the virus to the host cell. These observations suggest that the oxidative effect of CAP species inactivates the virus by hindering virus attachment and entry into the host cell. Furthermore, we found that the oxidative impact of plasma species led to oxidation and damage of viral RNA once it becomes unpacked due to capsid destruction. The latter effect most likely plays a secondary role in virus inactivation since the intact FCV genome is infectious even after damage to the capsid.

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Foodborne viruses, particularly human norovirus, are a concern for public health, especially in fresh vegetables and other minimally processed foods that may not undergo sufficient decontamination. It is necessary to explore novel nonthermal techniques for preventing foodborne viral contamination. In this study, aqueous extracts of six raw food materials (flower buds of clove, fenugreek seeds, garlic and onion bulbs, ginger rhizomes, and jalapeño peppers) were tested for antiviral activity against feline calicivirus (FCV) as a surrogate for human norovirus. The antiviral assay was performed using dilutions of the extracts below the maximum nontoxic concentrations of the extracts to the host cells of FCV, Crandell-Reese feline kidney (CRFK) cells. No antiviral effect was seen when the host cells were pretreated with any of the extracts. However, pretreatment of FCV with nondiluted clove and ginger extracts inactivated 6.0 and 2.7 log of the initial titer of the virus, respectively. Also, significant dosedependent inactivation of FCV was seen when host cells were treated with clove and ginger extracts at the time of infection or postinfection at concentrations equal to or lower than the maximum nontoxic concentrations. By comprehensive two-dimensional gas chromatography-mass spectrometry analysis, eugenol (29.5%) and R-(-)-1,2-propanediol (10.7%) were identified as the major components of clove and ginger extracts, respectively. The antiviral effect of the pure eugenol itself was tested; it showed antiviral activity similar to that of clove extract, albeit at a lower level, which indicates that some other clove extract constituents, along with eugenol, are responsible for inactivation of FCV. These results showed that the aqueous extracts of clove and ginger hold promise for prevention of foodborne viral contamination.