Modeling the effects of temperature and pH on Listeria monocytogenes growth in Mexican-style pork chorizo

Abstract

Temperature abuse often occurs during the elaboration and storage of Mexican-style pork chorizo that usually is prepared following a diversity of recipes with variations of the ingredients mainly the amount of vinegar added, causing fluctuation in the final pH of the product. The objective of this work was to study the effect and interaction of temperature (5-30°C) and pH (4.5-6.5) on the lag phase (LP), generation time (GT), and exponential growth rate (EGR) of Listeria monocytogenes inoculated in pork chorizo using response surface methodology. Regression models were developed to predict growth parameters. Predictive models were significant (p < 0.05), had no lack of fit (p > 0.05) and had an R2 > 0.94. These criteria indicate that the models satisfactorily describe the experimental data and can be used to estimate the LP, GT, and EGR of L. monocytogenes in pork chorizo as a function of pH and temperature within the studied limits. By simulating the growth of L. monocytogenes under temperature abuse storage and inadequate product's pH level, risk scenarios were identified. The optimal pH and temperature that maximize LP and GT, and minimize EGR were pH = 4.79 and temperature = 8.66 °C. Under these conditions, LP = 142 h, GT = 22.3 h, and EGR = 0.0135 Log (CFU/g)/h were predicted. Pork chorizo producers can use the models generated in this study to estimate the potential risk of L. monocytogenes growth as a function of the pH and temperature within the range established in this work.