Purpose: The purpose of this study was to (i) characterize the thermal inactivation behaviour of HAV in deli meat, (ii) compare first-order and Weibull models in describing the data in terms of selected statistical parameters, and (iii) calculate z-values and activation energy by each model.
Methods: Turkey deli meat purchased from a local market was cut into circular pieces (diameter = 3 cm). One-hundred µl of HAV with an initial titer of 7.27 ± 1.46 log PFU/ml was used to inoculate deli meat surfaces, and allowed to air-dry for 30 min under the biosafety cabinet. Inoculated samples were vacuum-sealed in a plastic bag to -100 kPa with a MultivacA300/16 vacuum-packaging unit. Sealed bags were placed into a holding unit prior to heating in a thermostatically controlled water-bath with temperature monitored by thermocouples. Survivor curves (D-values) and thermal death curves (z-values) were generated for different treatment times (0-6 min) at different temperatures (50, 56, 60, 65 and 72°C). Weibull and first-order models were compared to describe survivor curve kinetics and thermal death times. A comparison test (ANOVA, Post Hoc test) was used to analyze the effects of the temperature and time on survival ratio.
Results: Calculated D-values from the first-order model (50-72°C) ranged from 1.01 to 42.08 min for HAV. Using the Weibull model, the tD for HAV to destroy 1 log (D = 1) at the same temperature was 1.0 to 31.10 min. At 72°C, the required treatment time to achieve 6-log reduction was 6.06 min for the first-order model, and 6.92 min for the Weibull model. The z-value for HAV was 12.90 ± 0.64°C for first-order model and 16.36 ± 3.87°C for the Weibull model. The calculated activation energies for the first-order model and the Weibull model were 173 and 151 kJ/mole, respectively.
Significance: This study provides novel and precise information on thermal inactivation of HAV in turkey deli-meat enabling more reliable thermal process calculations to inactivate HAV and control outbreaks.