To the authors’ knowledge, a comparative assessment of DNAbased
quantification methods in the field of food allergen analysis
under pre-defined experimental framework conditions was performed
for the first time. Three quantification methods, the matrix-
adapted quantification, the quantification using an internal
standard material and the quantification by modified standard
addition were assessed using uniform performance criteria.
The matrix-adapted method shows a systematic divergence,
when the model-matrix differs from the sample matrix. The trueness
of the quantification results depends on the similarity of the
matrices. In principle, the corresponding model-matrix for each
examined sample or at least for each type of food (for example
boiled sausages) would be needed. This is reflected in the extreme
underestimation of the sesame content in boiled sausages and
muffin dough using breadcrumbs as model-matrix.
In contrast, the quantification method using an internal standard
material does not depend on a model-matrix. However, the
coefficient value needs to be determined for each batch of internal
standard material. In addition, high standard deviations of the
determined sesame contents were observed. The quantitative results
are calculated from initial target sequence copy numbers
determined using two independent real-time PCR systems. Therefore,
the variability of the copy numbers of both real-time PCR systems
contributes to the variation of the quantitative results.
Only the analyte of interest is needed for the quantification
using the modified standard addition, therefore, the quantitative
results do not depend on a model-matrix. Recoveries in the recommended
range of 70–120% were observed during the validation of
the method. The addition of the analyte to individual aliquots of
the sample material requires, however, at least four PCR analyses
per sample. Since only a DNA sequence specific for the analyte
needs to be detected, existing real-time PCR methods can be used
for the quantification of the allergen content without
modifications.