Development of a model describing the inhibitory effect of selected preservatives on the growth of Listeria monocytogenes in a meat model system

• A central composite design of 7 independent factors at 5 level was set up with 90 runs.
• They are NaCl, pH, nitrite, acetate, lactate, propionate and mixed nisin-Hop alpha acid.
• The anti-Listerial activity of 90 formulations were done during 90 storage days at 4 °C.
• A predictive equation based on analyzed data was found.
• The optimized conditions for controlling the growth of Listeria monocytogenes was also found.

The objective of this study was to evaluate the impact of seven independent factors consisting of sodium nitrite, pH, sodium chloride, sodium acetate, sodium lactate syrup, calcium propionate and a blend of nisin and hop alpha acids on the growth rate of Listeria monocytogenes in ham as a model of ready-to-eat (RTE) meat products. A central composite consisted of seven factors mentioned above was designed and the response surface methodology was applied for creating a mathematic model to predict the growth rate of L. monocytogenes in RTE meat products. Six parameters showed a significant (P ≤ 0.1) influence on the growth rate of L. monocytogenes. Only the blend of nisin and hop alpha acids did not show any significant effect (P > 0.1) in the concentrations used in this study. Increasing concentration of sodium chloride, sodium nitrite, sodium acetate, potassium lactate and calcium propionate in meat reduced bacterial growth rate while increasing pH in meat increased the growth rate of L. monocytogenes. The current mathematical equation will be an important tool in order to reduce the required number of challenge studies performed in order to ensure a safe food product.