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Oregano has been identified as one of the herbs most susceptible to adulteration. Methods based on DNA, spectroscopic analysis and even microscopy have already been used. In this paper, a new approach for authentication of oregano, which combines metabarcoding by NGS (next generation sequencing) and metabolomics/chemometrics by NMR, has been developed. The industry standard for oregano permits only 2% extraneous matter. A previous survey on oregano has shown that the most common plant adulterants are olive, sweet marjoram and myrtle leaves, and non-leaf plant material. In this study, 92 oregano, 38 sweet marjoram, and 2 olive leaf samples from 6 different countries in total were used. Metabarcoding by NGS was used to identify the nature of oregano products and possible adulterations. Metabolomic profiles obtained by NMR correlated well with oregano species and their regional origin. Using chemometric analysis, it was possible to quantify of the percentage of an adulterant with error rates of 3–7%.

Read the open access paper here

A Ph.D thesis from the University of Milan-Bicocca in English is publicly available. The thesis gives a good overview of DNA barcoding, NGS (Next Generation Sequencing) and metabarcoding, and isothermal nucleic acid amplification. The research carried out looked at applying DNA barcoding to processed foods, which required smaller DNA fragments. However, the approach is not suitable for mixed species samples, and NGS and metabarcoding approaches were more successful. Finally, an isothermal amplification assay was applied to authenticate truffles.

You can read the 253 page thesis here   

JRC (the EU Commission's Joint Research Centre) has just published a report summarising 20 years of EU funded projects on the development of emerging technologies to identify fish species and improve fish trade traceability. The report covers methods based on DNA amplification, DNA sequencing, DNA arrays, proteomics and chemical profiling.

Read the report at: JRC fish species report