Wild stenophylla coffee growing in forest in Sierra Leone. Photo by Aaron Davis, RBG Kew. Used with permission.
Five years ago, after embarking on a mission to find samples of the coffee species stenophylla in the wild in West Africa, renowned coffee plant scientist Aaron Davis spoke with Daily Coffee News about the species’ potential commercial appeal.
“We just don’t know,” Davis said in 2019. “It might be disgusting, but unless we give it a shot, we’ll never know.”
Much has changed in the five years since. Stenophylla has gotten its shot, with a high-profile tasting in late 2020 leading to a high-profile study in 2021 that told the world that stenophylla, in fact, could potentially offer flavors and cup scores in the same league as commercialized arabica.
Why does any of this matter?
According to the current protectors and proponents of stenophylla, it matters because the species — native to what is now Sierra Leone and other parts of upper West Africa — exhibits greater tolerance to heat as climate change threatens arabica production all over the globe.
Now, Davis and colleagues at Royal Botanic Gardens, Kew (UK) — including Eliot Jan-Smith and Melanie-Jayne Howes — have shined a light on why, chemically, stenophylla may offer similar flavors to arabica.
The research team also identified some chemical properties of the species — whose plants produce characteristic black ripe fruits as opposed to the deep reds or yellows of arabica — that may give it unique, differentiating qualities in the cup.
“Given similarities in flavour perception, yet differences in green bean chemistry, our study may be useful for gaining a better understanding of the chemical basis of coffee flavour,” the study authors wrote. “It may also offer opportunities for sensory diversification and thus coffee market differentiation, against a background of a changing climate and the need to sustain global coffee supplies for the future.”
In more direct terms, Jan-Smith told DCN, “The need to develop great tasting, climate resilient coffee is crucial to safeguarding the long-term sustainability of the speciality coffee sector.”
Green Coffee Chemistry Study
In an open-access study published March 19 in the Nature journal Science of Food, the researchers examined 26 different coffee samples of arabica, robusta and stenophylla.
Using liquid chromatography–mass spectrometry (LC–MS) and applied metabolomics approaches, the researchers measured key compounds that have proven to be associated with coffee’s sensory qualities, including caffeine, trigonelline, sucrose, and certain acids such as chlorogenic acids and citric acid.
Similarities to Arabica
One of the study’s standout findings is that stenophylla is comparable to arabica regarding several important molecules linked to flavor.
Caffeine, recognized for imparting bitterness and providing coffee’s signature stimulating effect, showed similar relative levels in both species — an outcome that helps explain why some tasters may have found stenophylla to exhibit an “arabica-like” taste.
The study also found similarities between stenophylla and arabica in: trigonelline, another compound associated with bitterness through roasting; sucrose, a precursor to desirable caramelization; and citric acid, one of the few organic acids detectable in brewed coffee.
Discovery of Theacrine
The researchers found that stenophylla is the first coffee species known to have the alkaloid theacrine, a compound that has been discovered in certain teas and is believed to affect taste.
While theacrine’s role in coffee remains to be studied, the authors suggested it could potentially contribute complexity to the cup or offer an alternative to caffeine.
Beyond the presence of theacrine, the researchers also found plenty of dissimilarities in the chemical composition of green stenophylla and arabica, including a potential chemical marker for arabica that the authors identified as “mozambioiside.”
They wrote, “While this study highlights the similarities in green bean chemistry between stenophylla and arabica, we also report clear dissimilarities between the two species.”
Moving forward, the authors call for more research into stenophylla, particularly in regard to potential commercial cultivation.
In a statement to DCN, Melanie-Jayne Howes said, “These novel insights into coffee chemistry show that there is potential to diversify the coffee experience, from both the sensory and quality perspectives, in a warming world.”
[Note: This story has been updated. The original version contained a photo that incorrectly identified arabica coffee as stenophylla. The photo was removed and a new photo has been included.]
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Nick Brown
Nick Brown is the editor of Daily Coffee News by Roast Magazine.
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