These tests provide a statement about whether Listeria monocytogenes can multiply in the food. This statement is very important for manufacturers of ready-to-eat, perishable foods for two reasons:

1. As part of their duty of care, every food business operator must ensure that their products do not pose a health risk until the end of shelf life. Because Listeria monocytogenes is widely distributed in the environment, contamination with these bacteria cannot be completely ruled out in the production of many foods. It is therefore important to know whether Listeria monocytogenes can multiply in these foods during their shelf life. If the growth of Listeria monocytogenes is favored, the hygiene and safety levels during production must be even higher.
2. The Regulation (EC) 2073/2005 on microbiological criteria requires in Annex I, Chapter 1 that certain food safety criteria for Listeria monocytogenes are met. Ready-to-eat foods that favor the multiplication of Listeria monocytogenes must not show Listeria monocytogenes presence in 5 samples of a batch, each 25g, at the production level (Criterion 1.2 in Chapter 1 of Annex I). If this is not complied with or this food safety criterion is exceeded, and the ready-to-eat food is already on the market, a public recall is threatened.

However, if ready-to-eat food does NOT favor the multiplication of Listeria monocytogenes, it is sufficient according to this regulation that the food safety criterion of 100 CFU/g is not exceeded in 5 sub-samples of the batch at the production level.

For ready-to-eat foods with a pH value of ≤ 4.4 or an aw value of ≤ 0.92, the food safety criterion of 100 CFU/g applies directly at the production level. The same applies if the ready-to-eat products have a pH of ≤ 5.0 and an aw of ≤ 0.94 or have a shelf life of less than 5 days. This is noted in the footnotes of Chapter 1 of Annex I of Regulation (EC) 2073/2005, as it is assumed in these cases that Listeria monocytogenes does not grow under these conditions, or the food safety criterion of 100 CFU/g for Listeria monocytogenes in ready-to-eat foods at the trading level is not exceeded.

The food business operator must provide this proof of the growth potential of Listeria monocytogenes in ready-to-eat foods to the authority. Otherwise, in case of doubt, the authority must assume that the stricter criteria for Listeria monocytogenes ("not detectable in 25g in each of 5 sub-samples of the batch") must be complied with for the products.

To provide this proof to the authority, contamination or challenge tests are required for many perishable foods unless the ready-to-eat food meets the above-mentioned chemical-physical properties or has a shelf life of less than 5 days.