Purpose: The purpose of this study was to (i) determine thermal inactivation kinetics of MNV-1 and FCV-F9 in spinach, (ii) compare first-order and Weibull models in describing the data, and (iii) measure the uncertainty associated with the process.
Methods: Thermal inactivation kinetics (D- and z-values) were determined for various treatment times at 50, 56, 60, 65 and 72°C in 2 ml vials. Weibull and first-order models were compared to describe inactivation kinetics. Statistical evaluation and linear and non-linear regression analyses were performed using SPSS Statistical package. The comparison test (ANOVA, Post Hoc test) was used to analyze the effect of time on survival ratio.
Results: z-values determined for MNV-1 were 11.66 ± 0.42 using the Weibull model and 10.98 ± 0.58 for the First-order model and for FCV-F9 were 10.85 ± 0.67 and 9.89 ± 0.79, respectively. There was no difference in D- or z-value using the two models (P > 0.05). Relative uncertainty for dilution factor, personal counting and test volume were 0.005%, 0.0004% and ca. 0.84%, respectively. The major contribution to total uncertainty was from the model selected. Total uncertainties for FCV-F9 for the Weibull and First-order models were 3.53-7.56% and 11.99-21.01%, respectively, and for MNV-1, 13.14-16.94% and 3.10-7.01%, respectively.
Significance: Novel and precise information on thermal inactivation of norovirus surrogates in spinach was generated enabling more reliable thermal process calculations to control the virus. Consideration of uncertainty measurements, which allow quantitative indication of analytic variability for any result, is needed to enhance validity of represented data.