Development of Probabilistic Model to Predict Lactobacillus spp. Growth as a Function of NaCl and NaNO2

Introduction: NaCl and NaNO₂ have been commonly used in processed meats, and Lactobacillus spp. are commonly isolated from the products. However, the effect of NaCl and NaNO₂ on Lactobacillus spp. has not been evaluated

Purpose: This study developed probabilistic models to evaluate the effect of NaCl and NaNO₂ on Lactobacillus spp. growth.

Methods: A five-strain mixture of Lactobacillus spp. was inoculated in MRS (deMan Rogosa and Sharpe) broth supplemented with NaCl (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and NaNO₂ (0, 15, 30, 45, 60, 75, 90, 105, 120, 150, 180, and 210 ppm), and all samples were aerobically and anaerobically stored at 4-15°C up to for 816h. Growth (assigned the value of 1) or no growth (assigned the value of 0) for each combination was determined by turbidity every 24h. These growth response data were then analyzed by the logistic regression to calculate the growth probability of Lactobacillus spp. as a function of NaCl and NaNO₂at each temperature. Subsequently, validation was conducted to evaluate the model performance.

Results: For aerobic storage, NaCl and NaNO₂ significantly (P < 0.05) inhibited Lactobacillus spp. growth at 4, 7, 10, and 12°C, and the obvious synergistic effect of NaCl and NaNO₂ was also observed to inhibit Lactobacillus spp. However, the synergistic effect was not observed at 15°C. In anaerobically stored samples, the significant effect of NaCl and NaNO₂ was observed at 4, 7, and 10°C, and the synergistic effect was of NaCl and NaNO₂ was observed up to at 12°C. Validation result showed that the developed models were appropriate to predict the growth probability of Lactobacillus spp. at different concentrations of NaCl and NaNO₂.

Significance: The probabilistic models developed in this study should be useful in determining optimum conditions to inhibit Lactobacillus spp.