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This study (open access) compared four different test approaches (DNA barcoding rbcL, DNA barcoding matK , ITS2 barcoding vs the NCBI database, ITS2 barcoding vs the BOLD database) in an authenticity survey of 100 herbal infusions on the Portuguese market.  Samples included 94 single-species products and six polyherbal formulations.

The authors report that DNA extraction was successful for 94 samples, while six single-species products failed to amplify any of the tested barcodes. Among the 88 remaining single-species samples, ITS2 showed the highest amplification success (100 %), outperforming the barcodes rbcL (94 %) and matK (84 %).

Sanger sequencing confirmed the labelled species in 69.3 % of cases with rbcL and 48.9 % with matK. While 63 samples would be considered authentic solely based on barcoding (i.e., if either rbcL or matK matched the label), ITS2 metabarcoding revealed that many of these contained additional undeclared species, indicating that barcoding alone overestimated product authenticity. Of the 85 samples successfully analysed by ITS2 metabarcoding, only 27 (32 %) fully matched their label, while 58 (68 %) contained either additional undeclared species or complete substitutions. Several products contained undeclared species in significant proportions, indicating potential economic adulteration.

The authors conclude that their results revealed (i) the importance of curated and comprehensive databases, with a higher number of species being identified by NCBI database, (ii) the superior sensitivity of ITS2 metabarcoding, and (iii) the widespread mislabelling in commercial herbal products.

Photo by Alice Pasqual on Unsplash

One of the frequently encountered types of adulteration is the adulteration of meat and animal products. In its most recent annual report [1] , the Food Fraud Network showed data that in the top ten product categories, fish and fish products take the second place, meat and meat products the third and poultry the fifth. Jointly, these three animal product categories eclipse any other product category.

There are different types of fraud that can be found in animal products. These include addition of illegal substances like melamine to milk, the treatment of tuna with carbon monoxide, and the replacement of high-quality species with lower quality ones, or even illegal ones. An example for this can be found in the publication by Fang and Zhang [2], where the addition of murine meat to substitute mutton has been reported.

Since there are many animal species that can be used for adulteration, using a species-specific PCR is often not economically viable when the adulterant species is not known. Here, the DNA barcoding approach is the better choice to cover a much wider range of species.

In the literature, numerous publications can be found that describe different primer sets to be used for barcoding. Unfortunately, not all methods have been thoroughly validated for the species they can, and, equally important, cannot detect.

The German §64 Food and Feed Law Methods Group for Animal and Plant Speciation has developed a tool that will help scientists to quickly determine which species can be detected and which cannot with a specific set of primers.

The tool, called BaTAnS – short for Barcoding Table for Animal Species – lists relevant publications, identifies the level of validation that has been performed for a specific method (and set of primers).

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