Temperature-assisted pressure inactivation of Listeria monocytogenes in Turkey breast meat

Ready-to-eat turkey breast meat samples were surface-inoculated with a five-strain cocktail of Listeria monocytogenes cultures to a final concentration of approximately 10(7) CFU/g. The inoculated meat samples were vacuum-packaged and pressure treated at 300 MPa for 2 min, 400 MPa for I min, and 500 MPa for I min at initial sample temperatures of 1, 10, 20, 30, 40, 50, and 55 degrees C. L. monocytogenes was most resistant to pressure at temperatures between 10 and 30 degrees C. As temperature decreased below 10 degrees C or increased over 30 degrees C, its pressure sensitivity increased. This enhanced inactivation effect was more pronounced when meat samples were treated at higher temperature than at lower temperature. For example, a 1-min treatment of 500 MPa at 40 degrees C reduced the counts by 3.8 loglo, while at I and 20 degrees C the same treatment reduced counts by 1.4 and 0.9 log(10), respectively (P < 0.05). The survival curves of L. monocytogenes were obtained at 300 MPa and 55 degrees C, 400 MPa and 50 degrees C, and 500 MPa and 40 degrees C. With increasing treatment time, the three survival curves showed a rapid initial drop in bacteria counts with a diminishing inactivation rate or tailing effect. The survival data were fitted with a linear and a nonlinear, Weibull, models. The Weibull model consistently produced better fit to the survival data than the linear model. (c) 2007 Elsevier B.V. All rights reserved.