Nonthermal inactivation of norovirus surrogates on blueberries using atmospheric cold plasma

Abstract

Viruses are currently the leading cause of foodborne outbreaks, most of which are associated with foods consumed raw. Cold plasma (CP) is an emerging novel nonthermal technology that can be used to surface decontaminate foods. This study investigated CP technology for the nonthermal inactivation of human norovirus surrogates, Tulane virus (TV) and murine norovirus (MNV), on the surface of blueberries. Blueberries (5 g) were weighed into sterile 4 oz. glass jars and inoculated with TV, 5 log PFU/g. Samples were treated with atmospheric CP for 0, 15, 30, 45, and 60 s at a working distance of 7.5 cm with 4 cubic feet/minute (cfm) of CP jet. Temperature readings were taken with an infrared camera prior to, and immediately following, CP treatments. In order to establish the impact of air flow during CP treatment (4 cfm), an additional 7 cfm jet of room temperature air was introduced from a separate nozzle. The experiment was repeated with 90 and 120 s as additional treatment time points. Viral titers were measured immediately after each treatment with a plaque assay using LLC-MK2 cells (TV) or RAW 264.7 cells (MNV). TV was significantly reduced 1.5 PFU/g compared to the control after treatment time of 45s, which was achieved regardless of temperature conditions. With the addition of 7 cfm of ambient air, the maximum log reduction for TV was 3.5 log PFU/g after 120s of treatment. MNV was significantly reduced by 0.5 log PFU/g compare to the control at 15s, and further treatment of MNV with ambient air brought the log reduction to greater than 5 log PFU/g at 90 s of treatment (Fig. 3). These results demonstrate that CP viral inactivation does not rely on thermal inactivation, and is therefore nonthermal in nature. With further optimization, CP may be used by food processors as a means of nonthermal inactivation of foodborne viruses.

Cold Plasma Inactivation of Escherichia coli O157:H7 Biofilms

“…Elimination of these pathogens from foods and food contact surfaces is a primary goal of sanitation programs and antimicrobial interventions. Cold plasma has recently gained attention as a potential tool for the food processing industry (Niemira, 2012a;Lacombe et al, 2017;Min et al, 2017). More specifically for the application of cold plasma to biofilms, a wide range of plasma technologies are currently being investigated which range in efficacy, speed of operation, feed gas composition, configuration, etc.…”

“…It is possible that longer treatment times beyond 15 s would engender thermal effects. While temperature control measures were not used in this study, other studies have used meaures such as forced air cooling to control untoward thermal effects (Lacombe et al, 2017).…”

“…Typically, high voltage electricity is used to ionize gas molecules into a reactive plasma, which can inactivate pathogenic bacteria and viruses (Bermúdez-Aguirre et al, 2013;Lacombe et al, 2017;Min et al, 2017). Cold plasma has also shown specific activity against biofilms, including biofilm-associated Salmonella, Listeria monocytogenes and E. coli biofilms (Brelles-Mariño, 2012;Niemira et al, 2014;Ziuzina et al, 2015).…”

Thermal Inactivation Kinetics of Tulane Virus in Cell‐Culture Medium and Spinach

“…Recently, multiple HNoV strains were reported to be cultivated in stem cell‐derived, nontransformed human intestinal enteroid monolayer cultures, though further optimization for higher titer replication as well as availability for various research labs and cost may be current hindrances for their routine use in testing and research (Ettayebi et al., ). Due to the current difficulty in assessing HNoV infectivity and current unavailability of animal models, animal caliciviruses such as murine norovirus (MNV‐1), feline calicivirus (FCV‐F9), porcine enteric sapovirus, and Tulane virus (TV) are used as surrogates for research purposes (Cromeans et al., ; D'Souza, ; Hirneisen & Kniel, ; Lacombe et al., , ).…”

Research Progress in Viral Inactivation Utilizing Human Norovirus Surrogates

“…Similar to human norovirus, TV binds to histo-blood group antigens and causes diarrhea in rhesus macaques (Farkas et al, 2008;Zhang et al, 2015). Additionally, other surrogates such as bacteriophage MS2 (Lacombe et al, 2017) and echovirus (Schiff et al, 1984) have also been used to study inactivation. In addition to viral surrogates, infectious human norovirus from human fecal specimens may also be used in combination with RT-qPCR.…”