Probabilistic Models to Predict Listeria monocytogenes Growth at Low Concentrations of NaNO(2) and NaCl in Frankfurters

This study developed probabilistic models to describe Listeria monocytogenes growth responses in meat products with low concentrations of NaNO(2) and NaCl. A five-strain mixture of L. monocytogenes was inoculated in NBYE (nutrient broth plus 0.6% yeast extract) supplemented with NaNO(2) (0-141 ppm) and NaCl (0-1.75%). The inoculated samples were then stored under aerobic and anaerobic conditions at 4, 7, 10, 12, and 15℃ for up to 60 d. Growth response data [growth (1) or no growth (0)] for each combination were determined by turbidity. The growth response data were analyzed using logistic regression to predict the growth probability of L. monocytogenes as a function of NaNO(2) and NaCl. The model performance was validated with the observed growth responses. The effect of an obvious NaNO(2) and NaCl combination was not observed under aerobic storage condition, but the antimicrobial effect of NaNO(2) on the inhibition of L. monocytogenes growth generally increased as NaCl concentration increased under anaerobic condition, especially at 7-10℃. A single application of NaNO(2) or NaCl significantly (p<0.05) inhibited L. monocytogenes growth at 4-15℃, but the combination of NaNO(2) or NaCl more effectively (p<0.05) inhibited L. monocytogenes growth than single application of either compound under anaerobic condition. Validation results showed 92% agreement between predicted and observed growth response data. These results indicate that the developed model is useful in predicting L. monocytogenes growth response at low concentrations of NaNO(2) and NaCl, and the antilisterial effect of NaNO(2) increased by NaCl under anaerobic condition.