Inactivation of Listeria innocua inoculated in liquid whole egg by high hydrostatic pressure

Abstract

The resistance of Listeria innocua, as a model microorganism for Listeria monocytogenes, to high hydrostatic pressure in liquid whole egg was studied at several pressures (300, 350, 400, and 450 MPa), temperatures (- 15, 2, and 20°C), and times (5, 10, and 15 min). Listeria innocua was added to liquid whole egg at approximately 106 CFU/ml. Listeria innocua was not totally inactivated in any of the treatments. In general, reduction was better at 2°C than at room temperature, but the greatest inactivation was obtained at 450 MPa at 20°C for 15 min (over 5 log of reduction). The results indicate that microbial inactivation was increased with prolonged exposure to pressure. D values for Listeria innocua were obtained at 400 MPa for two temperatures (2 and 20°C), and different times (0 to 20 min). The microbial inactivation followed apparent first-order kinetics, exhibiting a decimal reduction time of 7.35 min at 2°C and 8.23 min at 20°C.