Development of a predictive model for the growth of Listeria monocytogenes in fresh goat cheese “Jben” under varying temperature conditions

Listeriosis outbreaks have been linked to cheese consumption, prompting this study to focus on goat’s jben, a traditional Moroccan dairy product, to assess and model the growth of Listeria monocytogenes at various storage temperatures (4 – 30 °C). Lab-scale jben samples were prepared following a traditional Moroccan recipe and inoculated with a three-strain cocktail of L. monocytogenes at approximately 2 – 3 log CFU/g. These inoculated samples, with a pH = 6.701 ± 0.09 and aw = 0.915 ± 0.006, were stored under different isothermal conditions (4, 10, 20, 25, and 30 °C) and analyzed microbiologically using plate count methodology to quantify pathogen levels. Predictive microbiology models, utilizing mathematical equations, were employed to estimate microbial behavior in the product. The Baranyi model was used to describe the growth kinetics of cheeses stored under different temperature levels and was integrated with the Ratkowsky model through global regression analysis. This approach linked L. monocytogenes concentrations with storage temperature and time. Results showed that the pathogen's growth potential increased with higher storage temperatures. Analysis conducted using MATLAB provided estimated Ratkowsky model parameters: b = 0.0154 log CFU/h⋅°C, = 1.5 °C. Growth rates, modeled with the extended Ratkowsky square root model, ranged from 0.0118 to 0.1804 log CFU/h across the temperature range of 4 to 30 °C. The proposed model aims to predict L. monocytogenes growth over a wide range of storage temperatures, offering a foundation for making informed decisions about the microbiological safety of jben.