Purpose: This study developed predictive models to describe the effect of sodium chloride on inhibiting Pseudomonas and Salmonella growth in low-sodium nitrite frankfurters.
Methods: A five-strain mixture of Pseudomonas and a five-strain mixture of Salmonella were inoculated on low-sodium nitrite (0 and 10 ppm) frankfurters formulated with sodium chloride (1.0, 1.25 and 1.5%) at 3 log CFU/g. Pseudomonas (cetrimide agar) and Salmonella cell counts (xylose lysine desoxycholate agar) were enumerated during storage at 4, 10, and 15°C for up to 60 days under aerobic and vacuum storage. The modified Gompertz model was fitted to the growth data to calculate maximum specific growth rate (μmax; log CFU/g/h) and lag phase duration (LPD; h). The parameters were further analyzed with the square root model (μmax) and a polynomial model (LPD) as a function of temperature and sodium chloride. The model performance was evaluated by root mean square error (RMSE).
Results: Pseudomonas growth was observed (P < 0.05) only under aerobic storage. In frankfurters at 0 and 10 ppm of sodium nitrite, μmax of Pseudomonas decreased, but LPD increased as sodium chloride concentration increased. For both vacuum and aerobic storage, Salmonella growth was observed only at 10°C and 15°C, μmax of Salmonella growth was higher (P < 0.05) at 0 ppm than 10 ppm of sodium nitrite, and the antimicrobial effect of sodium nitrite became more obvious as sodium chloride concentration increased. RMSE from validation was 0.521 - 1.019.
Significance: This result indicates that the developed models should be useful in describing the sodium chloride effects on inhibiting Pseudomonas and Salmonella growth in low-sodium nitrite frankfurters.