LISTERIA-MONOCYTOGENES SURVIVAL MODEL VALIDATED IN SIMULATED UNCOOKED-FERMENTED MEAT-PRODUCTS FOR EFFECTS OF NITRITE AND PH

Previous modeling studies in broth cultures demonstrated that acidity and nitrite increased the inactivation rate of Listeria monocytogenes. To validate this effect during storage of simulated uncooked-fermented meat products, lean beef was ground with salt, adjusted to pH 4.0-5.1, and treated with nitrite at 0-300 mu g/mL. Samples were immediately inoculated with L. monocytogenes (10(7) CFU/g) and survivors were enumerated over 21 days storage at 37 degrees C. The time to achieve a four log decline as greatly affected by pH, ranging from 21 days at pH 5.0 to < 1.0 day at pH 4.0. Growth occurred at pH 5.1 after a long lag period. Nitrite additions did not affect survival, suggesting that the effective concentration was the rapidly decreasing residual nitrite level.