Estimating Listeria monocytogenes Growth in Ready-to-Eat Chicken Salad Using a Challenge Test for Quantitative Microbial Risk Assessment.

Currently, there is a growing preference for convenience food products, such as ready-to-eat (RTE) foods, associated with long refrigerated shelf-lives, not requiring a heat treatment prior to consumption. BecauseListeria monocytogenesis able to grow at refrigeration temperatures, inconsistent temperatures during production, distribution, and at consumer's household may allow for the pathogen to thrive, reaching unsafe limits.L. monocytogenesis the causative agent of listeriosis, a rare but severe human illness, with high fatality rates, transmitted almost exclusively by food consumption. With the aim of assessing the quantitative microbial risk ofL. monocytogenesin RTE chicken salads, a challenge test was performed. Salads were inoculated with a three-strain mixture of cold-adaptedL. monocytogenesand stored at 4, 12, and 16 degrees C for eight days. Results revealed that the salad was able to supportL. monocytogenes'growth, even at refrigeration temperatures. The Baranyi primary model was fitted to microbiological data to estimate the pathogen's growth kinetic parameters. Temperature effect on the maximum specific growth rate (mu(max)) was modeled using a square-root-type model. Storage temperature significantly influenced mu(max)ofL. monocytogenes(p< 0.05). These predicted growth models forL. monocytogeneswere subsequently used to develop a quantitative microbial risk assessment, estimating a median number of 0.00008726 listeriosis cases per year linked to the consumption of these RTE salads. Sensitivity analysis considering different time-temperature scenarios indicated a very low median risk per portion (<-7 log), even if the assessed RTE chicken salad was kept in abuse storage conditions.