Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2013
Publication Date: 9/6/2013
Citation: Li, X., Chen, H., Kingsley, D.H. 2013. The influence of temperature pH and water immersion on the high hydrostatic pressure inactivation of GI.1 and GII.4 human noroviruses. International Journal of Food Microbiology. 167:138-143. Interpretive Summary: In this publication, a recently developed PGM binding assay was used to assay for inactivation of human norovirus by high pressure processing (HPP). For the first time, use of this assay has provided a more detailed evaluation of optimal HPP conditions for human norovirus inactivation. Results indicate that refrigeration temperatures are ideal for HPP inactivation of human norovirus. Also the most common form of human norovirus, termed GII.4, is more sensitive to pressure than the prototype Norwalk strain, the only other previous human norovirus evaluated. Inactivation of norovirus on the surface of blueberries was also demonstrated. Curiously results indicate that acidic pH inhibits pressure inactivation of human norovirus, which has important implications for acidic juices and berry products treated by high pressure. Overall, this work can provide guidelines for industry when developing high pressure treatment protocols.
Technical Abstract: Detection of human norovirus (HuNoV) usually relies on molecular biology techniques, such as qRT PCR. Since histo-blood group antigens (HBGAs) are the functional receptors for HuNoV, HuNoV can bind to porcine gastric mucin (PGM), which contains HBGA-like antigens. In this study, PGM conjugated magnetic beads were used to collect and quantify potentially infectious HuNoV strains GI.1 and GII.4 treated by high hydrostatic pressure (HHP). Both GI.1 and GII.4 strains used in this study showed increasing pressure sensitivity as judged by loss of PGM binding with decreasing temperature over a range of 1 to 35 degrees C. Both GI.1 and GII.4 were more resistant to pressure at pH 4 than at neutral pH. Because GI.1 was significantly more resistant to pressure than GII.4, it was used to evaluate HuNoV pressure inactivation in blueberries. GI.1 on dry blueberries was very resistant to pressure while immersion of blueberries in water during pressure treatments substantially enhanced the inactivation. For example a 2 min 600 MPa treatment of dry blueberries at 1 and 21 degrees C resulted in greater than 1 log reduction while a 2.7 log reduction of GI.1 was achieved by a treatment at 500 MPa for 2 min at 1 degree C when blueberries were immersed in water. In total, this novel study provides unique information for designing pressure processing parameters (pressure, temperature, and time) and product formulations (such as pH) to inactivate HuNoV in high-risk foods such as berries.