Why are challenge tests with Listeria monocytogenes necessary? – Part 2
Nov 17, 2025 - Foods
Why are challenge tests with Listeria monocytogenes necessary? – Part 2
Regulation (EC) No 2073/2005 on microbiological criteria requires food manufacturers to comply with certain food safety criteria for Listeria monocytogenes in Annex I, Chapter 1. The categories 1.2 and 1.3 should be considered in more detail:
Category 1.3
Category 1.3 includes ready-to-eat foods in which the growth of Listeria monocytogenes is not favored. The permissible limit is 100 CFU/g in each of 5 sub-samples throughout the entire shelf life.
This category includes in particular foods with the following characteristics:
- pH value ≤ 4.4 or aw value ≤ 0.92
- pH value ≤ 5.0 and aw value ≤ 0.94
- Shelf life of less than 5 days
Products with these characteristics are automatically classified in this category. Other foods, such as frozen products, may also be assigned to this category with scientific justification.
Category 1.2
Category 1.2 concerns ready-to-eat foods in which the growth of Listeria monocytogenes is favored. It is divided into two criteria:
- If the food business operator cannot demonstrate that the level of Listeria monocytogenes does not exceed 100 CFU/g until the end of the shelf life, then the stricter criterion applies: "Not detectable in 25g in each of 5 sub-samples". It applies to manufacturers and, according to the amendment regulation (EU) No 2024/2895 from 01.07.2026, also at the trade level during the shelf life.
- If the food business operator can demonstrate that the product does not exceed the value of 100 CFU/g throughout the entire shelf life, then it applies: "Limit: 100 CFU/g" at the trade level during the shelf life.
To provide this evidence, it is necessary to take a closer look at Annex II of the Regulation (EC) No 2073/2005.
Article 3, paragraph 2 of Regulation (EC) No 2073/2005 refers to Annex II. The legislator requires that the food manufacturer must, if necessary, conduct investigations according to Annex II. These investigations are to ensure that the established criteria are met throughout the product's entire shelf life. This particularly concerns ready-to-eat foods in which the growth of Listeria monocytogenes is possible and that may pose a health risk to the public. These investigations include:
- Analysis of chemical-physical characteristics (e.g., pH value, aw value, salt content)
- Evaluation of scientific literature (e.g., on frozen foods considered non-growth promoting)
- Possibly additional investigations:
- Mathematical prediction models
- Challenge tests (with artificially contaminated foods)
- Storage trials (with naturally contaminated foods)
If assignment to category 1.3 is not possible due to the chemical or physical properties of the food and lack of or insufficient scientific studies, tests such as challenge tests can help determine whether the growth of Listeria monocytogenes is favored or not.
The third part will deal with the question "What are challenge tests?"
You can find our fact sheet on Listeria monocytogenes under the following link.
In our Tentamus laboratories, we regularly conduct examinations on Listeria monocytogenes as well as challenge tests with Listeria monocytogenes. We provide fast and reliable results.
Our customer advisors are happy to answer any questions you may have.
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