Red deer (Cervus elaphus)-specific real-time PCR assay for the detection of food adulteration

We present a red deer-specific real-time PCR assay which, combined with a reference real-time PCR assay published previously, allows the quantification of the red deer content in food products. Thus, it can be applied to detect food adulteration. The primer/probe system of the red deer-specific real-time PCR assay amplifies a 87 bp long fragment of the protein kinase C iota gene. To eliminate cross-reactivity with closely related species, the forward primer was designed to contain one deliberate base mismatch adjacent to one red deer-specific base. The red deer-specific real-time PCR assay did not show cross-reactivity with 23 animal and 50 plant species tested. LOD and LOQ, determined by analyzing a serially diluted DNA extract containing 1% (w/w) red deer DNA in pig DNA, were 0.05% and 0.4%, respectively. The accuracy was validated by analyzing DNA mixtures, meat extract mixtures, meat mixtures and model game sausages with known red deer content. The highest accuracy was obtained when the calibration mixture was similar to the analyzed sample in both the composition and concentration of the animal species of interest. High recoveries were not only obtained for raw samples but also after subjection to thermal treatment, including brewing (15 min at 75-78 °C), boiling (90 min at 100 °C) and microwave treatment (15 s, 40 s or 2 min at 650 W). The red deer-specific real-time PCR assay was found to be robust with respect to small deviations in the reaction volume or the annealing temperature and the use of another real-time PCR instrument.