1a. Objectives (from AD-416):
Objective 1: To determine whether an in vitro cultivable enteric monkey calicivirus, the Tulane virus, can be used as a surrogate for human NoV and to develop an organ culture and/or germ-free pig model to assess the survival of human NoV (Jiang, Li and Lee). Objective 2. To determine the effectiveness of four processing technologies (viz., high pressure processing, gamma irradiation, UV, and washing with sanitizers) on inactivation of human NoV, HAV and RV in, fresh and frozen berries (strawberries, raspberries and blueberries), berry purees, green onions, salsa and shellfish (Gurtler and Niemira). Objective 3. To determine the mechanism of viral inactivation by the four processing technologies. We will investigate whether viral capsid proteins, viral enzymes, genetic materials, and receptor binding activity are damaged or denatured by the processing technologies. (Jiang, Li, Lee, Chen, Wu, and Ozbay) Objective 4. To determine the effect of processing on the quality attributes of high risk foods. Sensory quality, important nutrients in the high risk foods, color, texture, and other important properties will be evaluated (Su, Chen, Wu, and Ozbay). Objective 5. To train graduate and undergraduate students in non-thermal processing technologies, food virology, and food safety; and to develop a “Foodborne Viruses and Food Safety” course and food virus module for classroom education nationwide (Chen, Wu, and Ozbay). Objective 6. To work with equipment manufacturers to design appropriate equipment for use in the targeted food products and to provide technical consultation to the food industry (Su, Chen, Wu, and Ozbay). Objective 7. To provide outreach education and training to the food industry and consumers in the area of foodborne viruses and food safety impacts of non-thermal technologies on high risk foods (Worobo and Pivnarik).
1b. Approach (from AD-416):
Contribute expertise related to gamma irradiation, high pressure processing, microbiology and food science, lab supplies and associated equipment. Collaborating universities will contribute to experiments, administer funds, hire and equip temp employee(s) and students in their campus labs, and coordinate the project. USDA-ARS, FSIT will undertake the research objective stated above. This will be accomplished by: Determining the effectiveness of four processing technologies (viz., high pressure processing, gamma irradiation, UV, and washing with sanitizers) on inactivation of human NoV, HAV and RV in fresh and frozen berries (strawberries, raspberries and blueberries), berry purees, green onions, salsa and shellfish. a. High pressure processing, and gamma irradiation in combination with GRAS antimicrobials will be evaluated for the elimination of human NoV, HAV and RV in fresh and frozen berries (strawberries, raspberries and blueberries), berry purees, green onions, salsa and shellfish. A greater than or equal to 5-log reduction will be tested at 700 MPa for 2, 4, 6, 8, 10, 12, and 14 min, 750 MPa for 1, 2, 3, 4, 5, 5, and 7 min, and 800 MPa for 0.5, 1, 1.5, 2, 2.5, 3, and 3.5 min. Gamma irradiation will be in dose ranges of 0 (control), 0.25, 0.5, 0.75, 1.0, 1.5, 2.0 kGy.
3. Progress Report:
ARS scientists and their post-doctoral research associate examined the effects of a surfactant and organic acids on inactivation of a surrogate virus, Tulane virus (TV), for human norovirus (NoV). Surrogates are needed because actual human NoV is nonculturable in the lab. We determined that exposing the surrogate TV to either 2% lactic acid (LA) + 2.8% sodium dodecyl sulfate (SDS) or 1% LA + 1.4% SDS at pH 3.8 can produce a 5 and 2 log PFU/ml reduction in TV, respectively. In addition, treatments of 0.5% LA + 0.7% SDS at pH 2.0 demonstrated a 5 log reduction. This information can be used to develop sanitizing washes to disinfect fresh fruits and vegetables, and prevent NoV outbreaks. ARS scientists worked together with collaborators from Ohio State University and University of Delaware (UD) to determine the effects of high pressure processing (HPP) on (A) human NoV, and (B) a potential surrogate NoV-like particle. It was determined that treating human NoV GII.4 strain for 5 min with 600 MPa of HPP prevented its binding to porcine gastric mucin cells by up to 5 log, and inactivated the virus (as determined by RT-PCR). Thus, it was concluded that VLPs (which are destroyed by HPP at 700 MPa, but not at 600 MPa) may be an effective HPP surrogate for human NoV, and that 600 MPa HPP for 5 min can inactivate human NoV. Further, ARS scientists, with collaborators from UD, examined the effects of post-processing storage conditions on HPP inactivation of Vibrio spp. in oysters. HPP at 300 MPa for 2 min, followed by 5-day ice storage or 7-day freezing, completely inactivated > 7 log Vibrio. This treatment regimen could be used to inactivate Vibrio spp. and prevent illnesses associated with oysters.