Purpose: This study developed mathematical models to determine optimum combinations of sodium chloride and sodium nitrite to prevent Enterococcus spp. growth in processed meat products.
Methods: A five-strain mixture of Enterococcus spp. was incubated in deMan, Rogosa and Sharpe (MRS) broth plus NaCl (0-1.75%) and sodium nitrite (0-120 ppm) at 4-15oC under aerobic and anaerobic conditions. Growth (referred to as 1) or no growth (referred to as 0) of Enterococcus spp. was determined by turbidity, and the growth response data were analyzed by the logistic regression to calculate the growth probability of the bacteria. The growth probabilities were validated to evaluate the model performance.
Results: In aerobic condition, at 4°C, the growth of Enterococcus spp. was not observed, but the growth of the bacteria in MRS broth was observed at 7-15°C, and higher sodium chloride concentration required low sodium nitrite concentration to inhibit Enterococcus spp. growth, and vice versa. However, at 120 ppm of sodium nitrite, sodium nitrite did not increase the inhibition of Enterococcus spp. For anaerobic condition, there was also no observation for Enterococcus spp. growth at 4°C, and at 7-12°C, Enterococcus spp. growth was inhibited at low sodium chloride concentration if sodium nitrite concentration was higher, and vice versa. At 15°C, single effect of sodium chloride on inhibition of Enterococcus spp. was not observed, but combination of sodium chloride and sodium nitrite inhibited Enterococcus spp. growth. Validation result suggested that the performance of developed probabilistic model was appropriate.
Significance: The probabilistic models developed in this study can determine optimum combinations of low sodium chloride and sodium nitrite concentration to inhibit Enterococcus spp. in processed meat products.