Deterministic Approach and Monte Carlo Simulation to Predict Listeria monocytogenes Time to Grow on Refrigerated Ham: A Study Supporting Risk- based Decisions for Consumers' Health

This study assessed the growth of Listeria monocytogenes in ready-to-eat (RTE) ham during storage under conditions simulating domestic practices with the intention to offer support in the elaboration of food safety policies that should better protect consumers against food poisoning at home. RTE ham, artificially contami-nated at either medium (102-103 CFU/g) or high (104-105 CFU/g) concentration, was stored at both isother-mal (4t in a refrigerator able to maintain a relatively constant temperature and 5t and 7t in a refrigerator with fluctuating temperature) and dynamic (5t and 7t with intermittent exposure to ambient temperature, e.g. 25t) conditions. Under isothermal conditions, the increasing storage temperature determined a signifi-cantly increased (p < 0.05) capacity of L. monocytogenes to grow. The kinetic growth parameters were derived by fitting the Baranyi and Roberts model to the experimental data and, based on the maximum specific growth rates, it was estimated the temperature dependence of L. monocytogenes growth in RTE ham. At medium con-tamination level, sanitary risk time calculation revealed that, unlike storage at 5t and 7t, storage at 4t of the RTE ham extends the time period during which the product is safe for consumption by similar to 40 and 52%, respec-tively. However, the real temperature fluctuations included in the Monte Carlo simulations at low L. monocy-togenes counts (1, 5 and 10 CFU/g) have shortened the safety margins. Stochastic models also proved to be useful tools for describing the pathogen's behavior when refrigeration of the RTE ham alternates with periods of ham being kept at room temperature, considered dynamic conditions of growth.

Automated summary

This study assessed the growth of Listeria monocytogenes in ready-to-eat ham during storage under conditions simulating domestic practices, aiming to provide support in the development of food safety policies for protecting consumers against food poisoning at home.