title: Determination of the thermal inactivation kinetics of the human norovirus surrogates, murine norovirus and feline calicivirus.
abstract: Studies are needed to bridge existing data gaps and determine appropriate parameters for thermal inactivation methods for human noroviruses. Cultivable surrogates, such as feline calicivirus (FCV-F9) and murine norovirus (MNV-1), have been used in the absence of human norovirus infectivity  assays. This study aimed to characterize the thermal inactivation kinetics of MNV-1 and FCV-F9 at 50, 56, 60, 65, and 72°C for different treatment times (0 to 60 min). Thermal inactivation was performed using the capillary tube method with titers of 4.0 × 10(7) (MNV-1) and  5.8 × 10(8) (FCV-F9) PFU/ml in triplicate experiments, followed by standard plaque assays in duplicate for each experiment. Weibull and first-order models were compared to describe survival curve kinetics. Model fitness was investigated by comparing the regression coefficients  (R(2)) and the chi-square (χ(2)) and root mean square error (RMSE) values. The D-values calculated from the first-order model (50 to 72°C) were 0.15 to 34.49 min for MNV-1 and 0.11 to 20.23 min for FCV-9. Using the Weibull model, the t(D)  values needed to destroy 1 log PFU of MNV-1 and FCV-F9 at the same temperatures were 0.11 to 28.26 and 0.06 to 13.86 min, respectively. In terms of thermal resistance, MNV-1 was more sensitive than FCV-F9 up to 65°C. At 72°C, FCV-F9 was slightly more susceptible to heat inactivation.  Results revealed that the Weibull model was more appropriate to represent the thermal inactivation behavior of both tested surrogates. The z-values were calculated using D-values for the first-order model and the t(D) values for the Weibull model. The z-values  were 9.31 and 9.19°C for MNV-1 and 9.36 and 9.31°C for FCV-F9 for the first-order and Weibull models, respectively. This study provides more precise information than previous reports on the thermal inactivation kinetics of two norovirus surrogates for use in thermal process calculations.
authors: Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
authors: Hayriye
authors: H
authors: Bozkurt
authors: Doris H
authors: DH
authors: D'Souza
authors: P Michael
authors: PM
authors: Davidson
mesh_terms: D000818:Animals; D019540:Area Under Curve; D017250:Caliciviridae Infections / Q000517:prevention & control; D017927:Calicivirus, Feline / Q000254:growth & development; D015169:Colony Count, Microbial; D005517:Foodborne Diseases / Q000517:prevention & control / Q000821:virology*; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D029322:Norovirus / Q000254:growth & development*; D038301:Virus Inactivation