The determination of ready-to-eat foods into Listeria monocytogenes growth and no growth categories by challenge tests

To assess the potential for a food to allow the growth of Listeria monocytogenes throughout its shelf life and be compliant with European Commission regulations, a challenge test was designed by the EU Community Reference Laboratory. The procedure for the determination of the growth potential includes the following: product characteristics, shelf-life of the product, number of batches, choice of the strain(s), preparation of the inoculum, preparation and inoculation of the test units, storage conditions, measurement of physico-chemical characteristics of the food and microbiological analysis to measure any increase in the pathogen load. The results are then used to assign a ready-to-eat food into a growth or no growth category, and if the food is able to support the growth of L. monocytogenes, to quantify the behavior of this bacteria in a food between production and consumption.