Samples of peanut butter and chocolate were prepared using the DNeasy mericon Food Kit (standard protocol) and products from 3 other suppliers to amplify a segment of the tnrL chloroplast tRNA gene. (A) Average quantification value (Cq) is substantially lower for samples prepared with the DNeasy mericon Food Kit compared to the other suppliers. (B) Using inhibitor-free DNA, this assay gives a positive Cq shift between 2.9–3.5 when samples are diluted 1:10; lower shifts indicate the presence of inhibitors. To test for inhibitors carried over from the sample preparation procedure, samples were diluted 1:10 and the same DNA segment was amplified. Both food samples were inhibitor-free when prepared with the DNeasy mericon Food Kit. Samples prepared with products from the other suppliers showed strong inhibitor contamination.
A plasmid carrying an artificial DNA sequence was amplified in reactions spiked with inhibitors and containing the Multiplex PCR Master Mix of the mericon PCR Assays or the master mix provided by Supplier AB. Inhibitors and concentrations simulated potential contaminations carried over from conventional sample preparation methods. The Multiplex PCR Master Mix demonstrated a superior protective capacity compared with Supplier AB.
The DNeasy mericon Food Kit enables DNA extraction from all food samples in radically shorter time compared to conventional CTAB protocols.