Scientists assess relevance of second analysis for food testing

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Experts in Belgium have given reasons why they believe a second analysis is not needed when doing microbiological testing.

The Scientific Committee of the Federal Agency for the Safety of the Food Chain (FASFC) proposed an amendment to the draft decree on the taking and analysis of samples in foodborne outbreaks. The advisory body provides advice on the assessment and management of risks in the food chain.

Experts said a second microbiological analysis is not scientifically relevant, given that the analysis of the first sample by an accredited laboratory provides a reliable assessment of the microbial safety of the lot.

Repeating the analysis, possibly on a sample from another lot where the bacterial flora may have evolved, will not provide a more accurate representation of initial contamination. The heterogeneity of contamination in lots is also a key factor, as the uneven distribution of microorganisms means that an initial positive result might not be reproduced during a second analysis, said experts.

Two-stage system
The operator still has the option to request a documentary examination, carried out by an independent expert, at their own expense.

Field sampling by FASFC for microbiological analyses of foodstuffs is carried out in two stages.

An initial sample is taken as part of an inspection at an operator’s premises. No measures are taken by the agency at this stage if the result of the analysis is non-compliant.

If the first sample is non-compliant, a new sample is taken from the company. At the same time, the operator is asked to take a sample for counter-analysis. This second sampling generally takes place at least one week to 15 days after the initial sampling.

This means it is possible that the first foodstuff or batch analyzed is no longer available. If this is the case, sampling is done on a different batch or a similar foodstuff.

If the result of this second sampling is non-compliant, action is taken by FASFC. These measures may be cancelled if the result of the counter-analysis is compliant.

Reasons for conclusion
The Scientific Committee said a second microbiological analysis is neither technically possible nor scientifically relevant for several reasons including the second sampling being carried out on different foods or batches.

Another issue is microorganisms are not distributed homogeneously in most matrices tested by FASFC. The presence of pathogens can vary considerably in batches. A first positive analysis indicating contamination, and a different result during a counter-analysis could reflect this variability rather than a real absence of contamination, especially if the levels are low.

Accredited laboratories perform the testing and are subject to audits and ring tests. The probability of false positives is low, and the Scientific Committee said it considers results of these labs to be sufficiently reliable to avoid the need for a second microbiological analysis.

A new scientific committee has also recently been selected. The chair is Dr. Lieve Herman, of the Research Institute for Agriculture, Fisheries and Food (ILVO), and vice-chair is Dr. Nicolas Korsak, from the University of Liège.

During the next four years, the 22 experts from the academic world and research institutes in Belgium will provide scientific advice to FASFC on a range of topics.

Bruno De Meulenaer is one of seven members from Ghent University, while Nick De Regge is one of four members from Sciensano, the Belgian national public health institute. 

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Source: https://www.foodsafetynews.com/2025/02/scientists-assess-relevance-of-second-analysis-for-food-testing/