The challenge of challenge testing to monitor Listeria monocytogenes growth on ready-to-eat foods in Europe by following the European Commission (2014) Technical Guidance document.

European Regulation (EC) No. 2073/2005 lays down the microbiological criteria for certain microorganisms in foods and the implementing rules to be complied with by food business operators (FBOs) in Europe when implementing general and specific hygiene measures. In relation to Listeria monocytogenes, this regulation covers primarily ready-to-eat (RTE) food products, and requires different microbiological criteria depending on the ability of the food product to support growth of L. monocytogenes. In addition, this regulation establishes that food safety is the responsibility of the FBO. The FBO can conduct studies to evaluate the growth of L. monocytogenes that may be present in the product during the shelf-life under reasonably foreseeable storage conditions of distribution, storage and use in order to investigate compliance with the criteria throughout the shelf-life of the product. The European Union Community Reference Laboratory for L. monocytogenes published a revised technical guidance document in June 2014 for conducting shelf-life studies on L. monocytogenes in RTE foods. This review article describes the recently published European guidance document, with special focus on the design of challenge studies to determine the growth potential of L. monocytogenes on foods. Information is given particularly on what a challenge test is and when one is advisable. The factors to be considered and the laboratory methodology to be applied when performing a challenge test to determine the growth potential of L. monocytogenes in a defined food matrix are also described. Results of recent research articles applying challenge tests to determine the growth of L. monocytogenes in a range of foodstuffs are summarized and discussed. Finally, recommendations for obtaining data that can contribute to any further revision of the guidance document and for addressing the main challenges of challenge testing for FBOs are presented.