Green tea extract assisted low-temperature pasteurization to inactivate enteric viruses in juices

The current popularity of minimally processed foods is an opportunity for natural antimicrobial agents to be combined with mild heat treatments to act synergistically in reducing viral foodborne pathogens. Viral inactivation by heat-treatments (at 25, 40, 50 and 63 °C for 30 min) combined with aged green tea extract (aged-GTE) was initially evaluated in phosphate buffered saline (PBS) against murine norovirus (MNV-1) and hepatitis A virus (HAV) by cell culture, and against human norovirus by in situ capture RT-qPCR. The combination of aged-GTE and heat treatment at 50 °C for 30 min exerted strong antiviral activity, reducing by more than 5 log MNV-1 infectivity in PBS. Heating at 40 °C for 30 min reduced the binding of norovirus to porcine gastric mucine (PGM) to 41.5% and the addition of aged-GTE further decreased the binding to 4.7%. Additionally, the reduction of MNV-1 and HAV infectivity was investigated in two different types of juices exposed to mild heat treatments alone, and combined with aged-GTE. The addition of aged-GTE increased to more than 4 log the inactivation of MNV-1 in juices exposed to 50 °C for 30 min. However, this synergistic effect of aged-GTE combined with heat treatments was not observed for HAV in any of the juices. Aged-GTE, then, could be considered as an additional control measure to improve the food safety of mild heat pasteurized juices.