A Machine Learning Approach to Predict Listeria monocytogenes Growth by Integrating FSSP and PMP Simulations: A Focus on t100 as a Possible Endpoint Parameters for Predictive Models

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Listeria monocytogenes is one of the most challenging foodborne pathogens for its psychrotrophic nature as well as the ability to grow under a wide range of environmental conditions; thus, food producers and regulatory agencies always search for new strategies to reduce the risk. In this context, predictive microbiology represents a valuable tool for supporting risk assessment and food safety management. This study investigated the time required for a 2-log increase in L. monocytogenes population (t100) as an integrated time-to-threshold endpoint and developed a simulation-derived modeling framework combining outputs from the Food Spoilage and Safety Predictor (FSSP) and Pathogen Modeling Program (PMP). After a preliminary analysis based on DoE (Design of Experiments) theory, the dataset was expanded with 300 additional simulations and used to compare different modeling approaches (e.g., nonlinear models and Random Forest regression). The optimized Random Forest showed the best internal predictive performance; temperature and NaCl were the dominant predictors, followed by nitrite and pH, whereas simulation source and initial inoculum showed lower additional contributions. A separate FSSP-specific analysis showed that the inclusion of lactic acid, an input variable of this tool, did not improve the predictive performance of the model. Concerning the accuracy of the model, it is worth mentioning that error increases for high t100 values and near the boundaries of the represented environmental space. Nevertheless, t100 provides a useful integrated endpoint for combining heterogeneous simulated growth responses. However, the proposed model should be regarded as a simulation-derived metamodel whose performance has been assessed only by an internal cross-validation. Independent validation through challenge tests in representative food matrices is required before its applicability to practical food-safety decision making.