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Is that really necessary, a challenge test?

Questions?
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We are regularly asked this question and our answer is often "yes, if...". In practice, it often turns out that the conditions to realize this "if" are very difficult and have considerable consequences for the product and/or the production process.

Listeria monocytogenes

The main reason for our response is the EU standard 2073/2005 and info page 85 of the NVWA. This includes specific requirements regarding the maximum limit values for Listeria monocytogenes for various types of food. This legislation states that in some cases 'additional studies' are required to ensure that Listeria monocytogenes cannot develop into unacceptable values.

Not necessary

There are a number of situations in which it is possible that the substantiation of the outgrowth does not have to be done by means of a challenge test. This is for example when:

  • The product has a low aw and/or pH
  • It's clear it's not a ready-made foodstuff
  • The product is pasteurized in the packaging
  • The shelf life of the product is less than 5 days

Please note that this is a guideline and whether this is actually sufficient, you can have it assessed by our experts.

Growth potential

Prior to performing a challenge test, a predictive calculation of the possible outgrowth of Listeria is performed. Based on the product properties and storage conditions, it is reasonable to predict what the growth will be during the shelf life. If it turns out that this growth is >0.5 log, then a challenge test should still be carried out to determine whether growth is actually taking place. A model calculation also serves to determine how many batches need to be tested during a challenge test.

Worst case scenario

Do you need to test all your products for the possible growth of Listeria? That is always possible, but it takes a lot of time and energy. It is easier and better to use a risk analysis to determine in which products the outgrowth is most likely to occur (high pH and/or aw or least conserved) and then to carry out the calculation on this and then to challenge it. Incidentally, this is not always easy, because the outgrowth depends on many factors.

Challenge test

For the execution of a challenge test, specific requirements apply that are mentioned in the EU technical guidance document. In contrast to a model calculation, in a challenge test the influence of the background flora is taken into account. This can influence the growth of Listeria monocytogenes, as a result of which in a few cases the result of a challenge test is more favorable than that of a model calculation.

Moving on...

What if the challenge test also shows that at the end of the shelf life Listeria monocytogenes is still above the standard? Then it is important to make product and/or process adjustments, so that one of the above situations is met. Please note that these adjustments also need to be substantiated by means of a calculation or challenge test.

Expertise

Eurofins Food Safety Solutions has a team of specialists who can assist you in substantiating the shelf life of your products. If you would like to know more, please feel free to contact the experts of Eurofins Food Safety Solutions via foodsafetysolutions@ftbnl.eurofins.com or +31 (0)88 8310330.

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