Survival and Inactivation by Advanced Oxidative Process of Foodborne Viruses in Model Low-Moisture Foods

Abstract

Enteric viruses, such as human norovirus (NoV) and hepatitis A virus (HAV), are the major causes of foodborne illnesses worldwide. These viruses have low infectious dose, and may remain infectious for weeks in the environment and food. Limited information is available regarding viral survival and transmission in low-moisture foods (LMF). LMFs are generally considered as ready-to-eat products, which undergo no or minimal pathogen reduction steps. However, numerous foodborne viral outbreaks associated with LMFs have been reported in recent years. The objective of this study was to examine the survival of foodborne viruses in LMFs during 4-week storage at ambient temperature and to evaluate the efficacy of advanced oxidative process (AOP) treatment in the inactivation of these viruses. For this purpose, select LMFs such as pistachios, chocolate, and cereal were inoculated with HAV and the norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), then viral survival on these food matrices was measured over a four-week incubation at ambient temperature, by both plaque assay and droplet-digital RT-PCR (ddRT-PCR) using the modified ISO-15216 method as well as the magnetic bead assay for viral recovery. We observed an approximately 0.5 log reduction in viral genome copies, and 1 log reduction in viral infectivity for all three tested viruses following storage of select inoculated LMFs for 4 weeks. Therefore, the present study shows that the examined foodborne viruses can persist for a long time in LMFs. Next, we examined the inactivation efficacy of AOP treatment, which combines UV-C, ozone, and hydrogen peroxide vapor, and observed that while approximately 100% (4 log) inactivation can be achieved for FCV, and MNV in chocolate, the inactivation efficiency diminishes to approximately 90% (1 log) in pistachios and 70% (< 1 log) in cereal. AOP treatment could therefore be a good candidate for risk reduction of foodborne viruses from certain LMFs depending on the food matrix and surface of treatment.

Keywords: Advanced oxidative process; Bead-based assay; Hepatitis A virus; Low-moisture foods; Norovirus surrogates.

Fig. 1

Log reduction of viral genome copies compared to T₀. FCV A-C, MNV D-F, and HAV G-I recovered by the ISO-15216 method and the bead-based method in inoculated pistachios, chocolate, and cornflakes over 4-week incubation determined by ddRT-PCR. The data represent the mean of six replicates. The Y axis is log reduction compared to T₀, the X axis is the time post-inoculation. Error bars represent standard deviation

Fig. 2

Log reduction in infectious viral particles for a FCV, b MNV, and c HAV over 4-week incubation determined by plaque assay. The ISO-15216 method was employed for virus recovery. The data represent the mean of six replicates. The error bars represent standard deviation

Fig. 3

Schematic presentation of the processes used in the Advanced Oxidative Process (AOP) unit, which is an instrument consisting of a conveyor belt that moves through a treatment chamber with spray nozzles that release hydrogen peroxide (6%) at a flow rate of 50 mL/min, 4 UV-C bulbs (254 λ, 82 ϕ/watts each), and 4 ozone generating bulbs (187 λ, 2.3 mg/h ozone each)

Fig. 4

The average log reduction in viral infectivity after treatment in AOP for 30 and 60 s for a FCV, b MNV, and c HAV compared to the untreated controls in all three LMFs. The data represent the mean of three replicates. The error bars represent standard deviation. *P < 0.01