Modeling the Effect of Low Concentration of NaCl and NaNO2 on the Growth Probability of Pseudomonas spp

Introduction: Recently, the consumers’ demand for low NaCl and NaNO₂ processed meat products has been increased, but microbial safety of the meat products has not been fully studied.

Purpose: This study developed probabilistic models to determine the optimum combinations of NaCl and NaNO₂ to produce growth-no growth interface of Pseudomonas spp. growth.

Methods: The combinations of NaCl (8 concentrations; 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and NaNO₂ (9 concentrations; 0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm) were prepared in nutrient broth, and placed in 96-well microtiter plate, followed by inoculation of a five-strain mixture of Pseudomonas spp. in each well. All microtiter plates were aerobically incubated at 4-15°C for 144-528h. Growth (referred to as 1) or no growth (referred to as 0) for each combination was then determined every 24h by turbidity. The growth response data were then analyzed by the logistic regression to produce probabilistic model for Pseudomonas spp. growth. Eventually, the predicted growth probabilities were compared to the observed growth to evaluate model performance.

Results: NaCl and NaNO₂ were significantly effective (P < 0.05) on inhibiting Pseudomonas spp. growth during storage at 4-12°C. The combination matrix composed of NaCl and NaNO₂ concentrations was prepared by the developed probabilistic model, and the result showed that at low NaCl concentration, higher NaNO₂ level was required to inhibit Pseudomonas growth at 4-15°C. However, at 15°C, there was no significant effect of NaCl and NaNO₂. A validation result showed that the performance of the probabilistic model developed in this study was appropriate.

Significance: The developed probabilistic models in this study should be useful in determining optimum conditions for low NaCl and NaNO₂ to inhibit Pseudomonas spp. growth in processed meat products.