Inactivation of hepatitis A virus and murine norovirus on surfaces of plastic, steel and raspberries using steam-ultrasound treatment.

The leading causes of foodborne viral disease outbreaks are human norovirus and hepatitis A virus (HAV). Their environmental persistence enables contamination of kitchen surfaces and crops often consumed raw, such as berries. Many decontamination procedures are inefficient and unsuitable for surfaces of industrial kitchen environments and soft fruits. In this study, we investigated the efficiency of a novel surface decontamination technology, combining steam and ultrasound (steam-ultrasound). Plastic, steel or raspberry surfaces were spiked with the norovirus surrogate, murine norovirus (MNV), and HAV, and steam-ultrasound treated at 85, 90 and 95 °C for 0-5 s. Post treatment viruses were titrated for survival by plaque assay and for genome stability by real-time quantitative PCR (RT-qPCR) of nucleic acid extracts. Survival of viruses were estimated in a log-linear model and the treatment time requirements for each decimal reduction (D value) in viral survival were calculated. The estimated D values of MNV or HAV were 0.4-0.2 or 1.1-0.8 s on plastic, 0.9-0.7 or 1.4-0.8 s on steel and 1.6-1.7 or 3.2-4.7 s on raspberries. No clear trend of genome reduction was observed with tested treatment parameters. Raspberries treated up to 4 s retained its natural texture and visual appeal similar to untreated controls whilst monitored for 7 days. In conclusion, steam-ultrasound treatment can within seconds reduce the titre of foodborne viruses on surfaces of plastic, steel and raspberries. This may particularly benefit industrial scale production of soft fruits for raw consumption and for swift non-hazardous decontamination of industrial kitchen surfaces.