Purpose: The purpose of this study was (i) to characterize the thermal inactivation behavior of HAV in clams, (ii) to compare first-order and Weibull models in describing the data in terms of selected statistical parameters, and (iii) to calculate z-values and activation energy for each model.
Methods: Fresh clams were purchased from a local seafood market and homogenized using a Waring blender. Five milliliters of HAV stock (7.04 ± 1.34 log PFU/ml) were added to 25 g of homogenized clams and held at 4°C for 24 h. An aliquot (6 ml) of the homogenized inoculated clam sample was added to moisture barrier vacuum-sealed plastic bags. Thermal inactivation was performed for up to 6 min at 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 temperature and time on survival ratio.
Results: The D-values for HAV were in the range of 47.37 ± 1.23 to 1.55 ± 0.12 min for the first-order model and 64.43 ± 3.47 to 1.25 ± 0.45 min for the Weibull model at temperatures ranging from 50 to 72°C, respectively. The z-values determined for HAV in clams were 12.97 ± 0.59°C using the Weibull model and 14.83 ± 0.0.28°C using the first-order model. The calculated activation energies for the first-order model and the Weibull model were 145 and 170 kJ/mole, respectively.
Significance: The results of this study could be used to develop commercial or home thermal process recommendations for clams with negligible risk for the presence of infectious HAV.