Challenge test: what, how and why?

As a food company, you must meet the requirements of the Dutch Food and Consumer Product Safety Authority (NVWA). This includes a study of the shelf life of your ready-to-eat food product. The challenge test is an indispensable part of this.

With a challenge test, our experienced expert team investigates the extent to which a microorganism can grow in your product. For example, you will know what Listeria monocytogenes does in your product in the event of contamination. We find this out by intentionally adding microorganisms and then measuring it.

According to what guidelines is a challenge test Listeria monocytogenes performed?

At Normec Foodcare, we perform challenge tests according to the 'EURL LM document Technical guidance document on challenge tests and durability studies for assessing shelflife of ready to eat foods related to Listeria monocytogenes', called TGD for short. This is the European guideline for challenge testing. It also follows additional requirements of the NVWA (Dutch Food and Consumer Product Safety Authority) in the Netherlands and the FAVV (Federal Agency for the Safety of the Food Chain) in Belgium. A big advantage is that with challenge testing you immediately meet the requirements described in Information Sheet 85 and also already Manual 85.

This is how a challenge test works

We take a measurement at the beginning (day 0), as well as several moments during and at the end of the test's shelf life. This is how we calculate how Listeria monocytogenes grows and we determine whether the product serves as a breeding ground for Listeria monocytogenes can serve. If this is the case, you can use the result of the challenge test to establish intermediate limits to ensure that the limit (as in Listeria monocytogenes: 100 cfu/g) is not exceeded to during the shelf life.

During the challenge test we also include various parameters, including, for example, preservation, pH, salt, water activity and other microorganisms such as general germ count, yeasts and fungi and lactic acid bacteria. This gives you a complete picture about the growth and/or inhibition of Listeria monocytogenes.

Substantiation of production batches

With only measuring the Listeria monocytogenes you're not there yet. There is an increasing scrutiny of the substantiation of the production batches used in the test. Before the food company commissions a challenge test from a laboratory, the company must have relevant information on the product to be tested. Among other things, this information must be used to demonstrate that the products examined during the challenge test are representative of the regular production batches produced by the company. For example, production processes and specific product characteristics (such as preservatives, salt, pH, etc.) of the food product under investigation are requested, including variability between and within production batches.

To ensure that variability, a preliminary study can be conducted prior to the challenge test in which a minimum of five pH and aw measurements are requested per batch and for a minimum of three product batches (from different production days).

Want to know more?

Still have questions about the challenge test or want to know more about how to prevent Listeria outbreak. The specialists of Normec Foodcare have years of experience and are ready to support you where needed.