snps (3)

4156897705?profile=RESIZE_710xIn a first for food authentication, German researchers have developed a new CRISPR/Cas9 based in vitro assay to distinguish a fine cocoa variety from a bulk cocoa variety. Ecuador is a major supplier of a fine single cocoa Variety Nacional (Arriba), but also produces a cheaper but less aromatic bulk cocoa “Colección Castro Naranjal 51” (CCN-51).  There are several characteristic SNPs (single nucleotide polymorphisms) that could be used to distinguish these two varieties. However, the detection of single base exchanges in order to differentiate raw material types or varieties is challenging, as some of the methods require the use of restriction endonucleases. The use of the programmable Cas9 endonuclease known from the genome editing system CRISPR/Cas9 is a powerful alternative. The detection of bulk cocoa in fine cocoa uses a SNP which is located within a PAM region (protospacer adjacent motif) mandatory for the Cas9 endonuclease. Consequently, only the bulk cocoa is attacked by the nuclease. The result can be recorded using agarose or capillary gel electrophoresis (AGE and CGE). Both methods yielded comparable results. AGE can be used for a semi-quantitative estimation and the more sophisticated CGE for quantitation based on a calibration line. The assay could reliably detect 10% CCN-51in an admixture with Arriba, which is a realistic level for routine applications.

This approach could be adapted to other authenticty applications which use SNPs for variety or species identification. Read the abstract here

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3823828176?profile=RESIZE_710xGreek researchers have evaluated using DNA markers SNPs (single nucleotide polymorphism) and SSRs (simple sequence repeats) combined with high resolution melting (HRM) to authenticate monvarietal olive oils and the quantitative determination of adulteration with other plant oils (maize and sunflower oils). The SSR-HRM was more efficient in distinguishing monovarietal olive oils, while the SNP-HRM assay was more reliable in discriminating olive oil blends. HRM was also used for the detection of adulteration of olive oil with oils of different plant origin by using plastid trnL indels and SNPs. The trnL-indels-HRM showed higher discrimination power than the trnL-SNP-HRM in determining adulteration in olive oil. 

Read the full paper here

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This open access chapter reviews the current DNA approaches to authenticating olive oil by identification of the variety or the plant species from which it was extracted. The chapter examines the current trends and critical issues on DNA targeted approaches used for traceability and authenticity of olive oil in this rapidly expanding field.

Read the chapter at: DNA based methods for olive oil

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