NONTHERMAL INACTIVATION MODELS FOR LISTERIA-MONOCYTOGENES

The effects of temperature, lactic acid (or pH), sodium chloride, and sodium nitrite on the non-thermal inactivation of a three strain mixture of Listeria monocytogenes were examined in brain heart infusion broth. A total of 249 survivor curves representing 157 combinations of the four variables were generated. The survivor curves were described mathematically by fitting data using linear and nonlinear primary models. Supplemental studies demonstrated that (1) preculturing the microorganism in an acidic environment or in media containing glucose increased acid tolerance, (2) survivor curve tailing was not due to the presence of a more resistant subpopulation, and (3) the rate of nonthermal inactivation was independent of initial population density. Response surface models were developed for predicting the effects and interactions of the four independent variables on the inactivation of Listeria monocytogenes under adverse environmental conditions.