Probabilistic Models to Predict Listeria monocytogenes Growth at Low Concentrations of NaNO₂and NaCl in Frankfurters

Abstract

This study developed probabilistic models to describe Listeria monocytogenes growth responses in meat products with low concentrations of NaNO2 and NaCl. A five-strain mixture of L. monocytogenes was inoculated in NBYE (nutrient broth plus 0.6% yeast extract) supplemented with NaNO2 (0-141 ppm) and NaCl (0-1.75%). The inoculated samples were then stored under aerobic and anaerobic conditions at 4, 7, 10, 12, and 15℃ for up to 60 d. Growth response data [growth (1) or no growth (0)] for each combination were determined by turbidity. The growth response data were analyzed using logistic regression to predict the growth probability of L. monocytogenes as a function of NaNO2 and NaCl. The model performance was validated with the observed growth responses. The effect of an obvious NaNO2 and NaCl combination was not observed under aerobic storage condition, but the antimicrobial effect of NaNO2 on the inhibition of L. monocytogenes growth generally increased as NaCl concentration increased under anaerobic condition, especially at 7-10℃. A single application of NaNO2 or NaCl significantly (p<0.05) inhibited L. monocytogenes growth at 4-15℃, but the combination of NaNO2 or NaCl more effectively (p<0.05) inhibited L. monocytogenes growth than single application of either compound under anaerobic condition. Validation results showed 92% agreement between predicted and observed growth response data. These results indicate that the developed model is useful in predicting L. monocytogenes growth response at low concentrations of NaNO2 and NaCl, and the antilisterial effect of NaNO2 increased by NaCl under anaerobic condition.

Mathematical Model for Predicting the Growth Probability of Staphylococcus aureus in Combinations of NaCl and NaNO2under Aerobic or Evacuated Storage Conditions

“…Because the predictions from the developed probabilistic models were expressed as numbers, growth was determined at more than 0.5 of growth probability (Yoon et al , 2012). In addition, growth responses (growth or no growth) from the sausages were determined at 1 Log CFU/g of S. aureus growth (Gwak et al , 2015; Koutsoumanis et al , 2004). Comparisons between predicted and observed growth response are presented in Table 3; the observed growth responses mostly agreed with the predicted growth responses.…”

“…During storage, S. aureus cell counts were enumerated on MSA (Becton, Dickinson and Company). If the S. aureus cell count increased by more than 1 Log CFU/g compared with that on day 0, the result was considered to be “growth”, otherwise “no growth” was recorded (Gwak et al , 2015; Koutsoumanis et al , 2004). …”

Evaluation of <i>Salmonella</i> Growth at Low Concentrations of NaNO₂ and NaCl in Processed Meat Products Using Probabilistic Model

“…Thirty frankfurters were immersed in 500 mL inoculum (3 log CFU/mL) in a sterilized plastic container for 2 min. The samples were air-dried under a laminar flow cabinet for 15 min to allow Salmonella attachment then transferred into vacuum bags ( Gwak et al, 2015 ). The bags were sealed for aerobic storage or vacuum packaged for anaerobic storage using a vacuum packager (HFV-500; Fujee Inc., Hwaseong, Korea).…”

Microbiological safety of processed meat products formulated with low nitrite concentration — A review

“…Therefore, microbiological safety of processed meat products with lower nitrite levels can be improved by a combination of pH and sodium chloride concentration. Gwak et al [ 7 ] and Tompkin [ 40 ] have also suggested that increased sodium chloride levels can control the growth of harmful bacteria in processed meat products with lower nitrite concentrations because the antimicrobial effect of nitrite is influenced by sodium chloride concentration, pH, reductants, iron content, and so on.…”

“…Meat products with lower nitrite (below conventional concentration of products) concentrations have been produced [ 5 ]. However, Doyle and Glass [ 6 ], and Gwak et al [ 7 ] have suggested that there are problems related to microbial safety of processed meat products with no or low nitrite concentrations. Therefore, the objective of this short communication was to review food safety of processed meat products formulated with no or low nitrite concentrations.…”