High hydrostatic pressure processing (HPP) is an innovative nonthermal technology that allows for pathogen inactivation and maintains the raw character of foods such as oysters, salsa, guacamole, ready-to-eat meats, and juices. Compared to thermal processes HPP has an insignificant effect on flavor compounds, vitamins, and pigments. It is important that consumers and industry understand and accept the use of HPP to inactivate viruses like hepatitis A virus, Aichi virus, and norovirus.

A large percentage of foodborne outbreaks are caused by viruses. Hepatitis A virus (HAV) is a human enteric virus causing an illness characterized by sudden onset of fever, malaise, nausea, anorexia, and abdominal pain, followed by jaundice. Water, shellfish, and salads are the most commonly implicated food sources in HAV outbreaks. There are an estimated 83,000 HAV cases in the U.S. each year. Aichi virus (AiV) was first recognized in 1989 in Japan. AiV causes gastroenteritis and is often associated with the consumption of oysters. Norovirus (NoV) is a major cause of foodborne illness in humans with an estimated 23 million illnesses each year in the United States. NoV is a highly contagious virus causing gastroenteritis, and can be spread by water, air, person-to-person contact, or through contaminated foods. Feline calicivirus (FCV) is used as the laboratory surrogate for NoV.

Salsa was chosen as a model food in this study because there have been foodborne outbreaks involving green onions and tomatoes, both ingredients found in salsa products. Oyster slurry was chosen as a model food because raw oysters are often associated with foodborne illnesses. Salsa and oyster slurry samples were inoculated with a known concentration of virus (HAV, FCV, and AiV) and treated for 1, 5, and 10 min at 9°C at 250, 400, and 500 MPa. Samples inoculated with the pressure-resistant AiV were additionally treated with pressure-treatment temperatures of 50°C, 60°C, and 80°C. The virus was recovered, serially diluted, and analyzed for infectivity using TCID₅₀ in mammalian cell culture. No virus activity was observed after a 400 MPa (1 min) treatment for HAV and FCV was inactivated after a 250 MPa (1 min) treatment in fresh salsa. HAV was reduced by 7-log TCID ₅₀/ml and FCV was reduced by 6.5-log TCID₅₀/ml. After a 250, 400, and 500 MPa, 5 min treatment in oyster slurry, HAV was reduced by 1.37-log, 2.39-log, and 2.21-log TCID₅₀/ml, respectively. FCV in oyster slurry was reduced by 6.77-log TCID₅₀/ml after 250 MPa, 5 min treatment. There was no reduction of AiV seen with all pressures tested (250, 400, and 500 MPa) in both salsa and oyster slurry until the mixture was heated which was effective in reducing the virus. HPP has been shown to inactivate viruses including HAV and FCV, and can be used for ready-to-eat foods like salsa. Salinity of oyster slurry has an obvious protective effect on the viruses.

Knowledge gained from successful inactivation of viruses in a fresh salsa product or oyster slurry by HPP is beneficial information for consumers and industry. This work will help consumers become aware of the importance of this technology and accept its use in industry.