Modeling the Effect of Temperature on the Growth Rate and Lag Time of Listeria innocua and Listeria monocytogenes.

Several mathematical models which predict growth rate and lag time as a function of temperature were compared. The growth rate and lag time of Listeria innocua PFEI and Listeria monocytogenes Scott A PFEI were determined in brain heart infusion broth between 275 and 319 K. TableCurve 3.01 was used to fit model parameters to the L. monocytogenes data and to evaluate growth rate and lag time models. The growth rate models were validated using L. monocytogenes data from real dairy food systems. L. innocua grew faster than L. monocytogenes at temperatures below 315 K and grew slower than L. monocytogenes at temperatures higher than 315 K. At temperatures below 281 K, the lag time of L. monocytogenes was longer than that of L. innocua . The r and F values show that the 4-parameter growth rate models fit the data better than the 6-parameter models. The 4-parameter Zwietering Square Root Model gives the best fit of all the models used to predict growth rate. The 2-parameter models predict lag time better than the models containing more parameters. The 2-parameter Square Root Model gives the best fit of all the models evaluated when a traditional method of determining lag time is used. The 2-parameter New Model gives the best fit of all the models, when the Solberg method of determining lag time is used. Four growth rate models are not only suitable for modeling the growth rate of L. monocytogenes in brain heart infusion broth but are also suitable for modeling its growth rate in the selected real dairy food systems.