A Coffee Testing Question


As science advances, so does the complexity of the world it unleashes. Take the coffee business, for example. Single-serve technologies, cold-brew techniques, and nitrogen infusion, among others, have changed the way coffee is packaged, brewed, and served.

Each change offers advantages, but also new challenges. Single-serve delivers convenience, but has posed recycling complications. Cold-brew offers smoother coffee, but calls for special food-safety techniques.

On a molecular level, genetics have decoded the Robusta genome, but not that of Arabica. Testing techniques can now detect coffee DNA within samples, but are more advanced than the body of knowledge on which they base results. Without adequate information and validation, modern testing techniques can yield misleading results.

That’s why a popular new methodology – “SNP” for its use of Single Nucleotide Polymorphisms – cannot accurately verify whether roast-and-ground coffee comes exclusively from Arabica beans. In fact, Arabica is a natural cross between a species called Coffea eugenioides and Robusta and, evolutionarily, a young species at just one million years old.


Arabica and Robusta coffee cherries. Photo: Highroad Coffee

So, coffee labeled “100% Arabica” – which has become a marketing mantra as well as scientific distinction – actually contains genetic material from its Robusta parent. It’s possible to determine Robusta’s genetic makeup since the genome has been decoded. But, what blend of genetic material from Robusta and from C. eugenioides constitutes pure Arabica awaits the decoding of its genome.

Furthermore, extracting DNA from roasted coffee is highly unreliable. The quantity and quality of the DNA will be very low, since roasting temperatures degrade the DNA. In fact, the degradation breaks down the DNA into its basic components, known as amino acids, which are the same across all plant organisms. Reliable coffee DNA should be extracted from fresh leaves or green coffee beans, and it should be matched against samples retained by an expert botanist. Bottom line, the ability to extract viable DNA fragments from roasted coffee is low to zero.

Science offers other tests, however, that pick up a natural oil that is found in Robusta and not Arabica.

The substance, known as 16-o-methyl cafestol, can be detected with good sensitivity by analytic testing techniques such as liquid chromatography (LC). If Robusta has been mixed into Arabica roast-and-ground coffee, LC will pick up the presence of the oil. Additionally, any Robusta in a brewed Arabica coffee even approaching as little as 5%, would easily be detected by coffee “cuppers,” on whose expertise roasters rely to ensure the quality of their products.

If you have questions, contact Joe DeRupo at jfderupo@ncausa.org, who will consult with members of the NCA Scientific Advisory Group for answers.


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