Requirements for food matrices

Food matrices significantly influence the results of analysis, and the sampling procedures and methods used for analysis generally depend on the matrix information.

Samples composed of several ingredients of different characteristics are more difficult to handle, whereas liquid samples are generally considered homogeneous or easy to homogenize by shaking.

An example of this is cereal bars, which may have an uneven distribution of allergens in a single component, as they are usually composed of different dispersed ingredients. They must therefore be thoroughly homogenized before test samples are taken for analysis.

Sometimes certain types of analysis can give false positives or negatives, due to certain components present in the matrix that make it unsuitable for such analysis.

Examples of these components can be tannins or polyphenols, which can mask the presence of allergens. On other occasions the results may give a false positive, due to the presence of compounds very similar to the allergenic substance being detected.

There are other components that can affect the results, those with high acid values can damage the DNA and prevent DNA detection, and allergenic proteins may still be present. Depending on the process, a high level of sugar may disrupt DNA extraction.

Ethanol, if present, can cause false negative results because it denatures the antibodies. Therefore, it is highly recommended to provide all the information about the composition of the sample prior to analysis, so that the laboratory can select the appropriate method for analysis. Ideally, however, the laboratory should receive from the manufacturer an allergen-free sample of the food matrix containing the allergen, verified by another method, so that the laboratory can validate the preparation and detection of the sample.

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