What should be considered when conducting stress or challenge tests with Listeria monocytogenes?

A technical guideline (EURL Lm TECHNICAL GUIDANCE DOCUMENT for conducting shelf-life studies on Listeria monocytogenes in ready-to-eat foods) was published by the EU Commission, which describes the procedure for conducting challenge tests with Listeria monocytogenes.

Some important aspects of it:

• The conditions during the shelf life must be considered (including foreseeable changes compared to the information on the packaging, such as refrigerator temperatures in households).
• A mixture of at least 2 strains of Listeria monocytogenes should be used for contamination. Not only laboratory strains should be used, but also strains isolated from similar foods or even from the respective food company.
• The food should be contaminated at the beginning of the challenge test with a germ concentration of about 100 CFU/g.
• DIN EN ISO 20976-1:2019-09 (https://www.beuth.de/de/norm/din-en-iso-20976-1/297296778)