Modeling the effects of temperature, sodium chloride and green tea and their interactions on the thermal inactivation of Listeria monocytogenes in turkey

The interactive effects of heating temperature (55 – 65C), sodium chloride (NaCl, 0-2%), and green tea 60% polyphenol extract (GTPE, 0-3%) on heat resistance of a five-strain mixture of Listeria monocytogenes in ground turkey were determined. Thermal death times were quantified in bags submerged in a circulating water bath set at temperatures 55, 57, 60, 63, and 65C. The recovery medium was tryptic soy agar with added 0.6% yeast extract and 1% sodium pyruvate. The D-values obtained were analyzed by second order response surface regression for temperature, NaCl and GTPE. The data indicated that all three factors interacted to affect the inactivation of the pathogen. The D-values obtained for turkey with no NaCl or GTPE at 55, 57, 60, 63 and 65C were 36.32, 20.84, 13.15, 4.13 and 2.88 min, respectively. While NaCl exhibited a concentration-dependent protective effect against heat lethality on L. monocytogenes in turkey, addition of GTPE rendered the pathogen more sensitive to the lethal effect of heat. GTPE levels up to 1.5% interacted with NaCl and reduced the protective effect of NaCl on heat resistance of the pathogen. Food processors can use the predictive model to design an appropriate heat treatment for inactivating L. monocytogenes in cooked turkey products without adversely affecting the quality of the product.