A Note from Jenny: Discovering Mamuto's DNA
A Genetic Testing Project
June 16, 2026
For years, we believed Mamuto’s distinctive blackberry and blackcurrant notes - now incredibly rare in Kenya - came from the SL28 variety. These flavors have come to define Mamuto and, in many ways, have become an international reference point for what buyers seek in Kenyan coffee. So, we set out on a journey to understand exactly what contributes to these famous tasting notes and how we could preserve them.
Our first step was to find out exactly what was growing at Mamuto. We never had definitive proof of what was actually planted, so we needed to identify the coffee varieties growing across the farm.
That curiosity led us to begin genetic testing.
Mamuto has six plots in total. The oldest was planted in the 1960s, making some trees more than 65 years old, with additional plots established in the 1970s, 1980s, and 1990s. When the farm originally received seedlings, they were all believed to be SL28.
Last year, we tested that assumption by analyzing the DNA of ten green coffee beans. The results were surprising: we found SL34, K7, SL09, and even one Batian, but not a single SL28. SL34 is also known for sweet blackberry notes, while K7 and SL09 are predecessors of SL28. Batian, a newer climate-resilient hybrid, has not yet shown the flavor profile we seek. You will notice Mamuto’s label has changed to reflect the true varieties contributing to its sweet blackberry note: SL34 and heirloom varieties.
This discovery launched our formal, long-term DNA identification project. Over the next four to six years, our goal is to determine where Mamuto’s signature blackberry character truly comes from, and, eventually reproduce those genetics through a dedicated nursery.
On my most recent visit, I began that work by walking the farm’s two oldest plots. Together, they contain roughly 600 trees. I selected, tagged, photographed, and collected leaf samples from 15 trees for DNA testing.
When harvest arrives in October, those identified trees will be harvested separately and cupped individually. This is delicate work - each tree may produce only two pounds of coffee cherry, yielding about half a pound of green coffee for evaluation. We will repeat this process year after year as we work to isolate the source of this remarkable flavor.
What’s been truly exciting is how spectacular this year’s crop has been, showcasing Mamuto’s signature syrupy blackberry note with remarkable clarity and deep sweetness. Quite simply, it is one of the best harvests we’ve ever had.
In addition to understanding the true DNA of Mamuto’s beans, we’re also learning that greater genetic diversity on a farm can improve climate resilience. As the project evolves, we continue to uncover new insights and will share those discoveries along the way.
Over the years, we have collaborated on many projects at Mamuto: adding drying beds, conditioning bins, and storage buildings; introducing moisture meters; and continuously refining processes to improve quality. This DNA project feels like a natural continuation of that shared commitment. Our hope is that, together we can preserve one of coffee’s most special and elusive flavors while creating a source of knowledge for others along the way.
What made our last visit to Mamuto in January of 2026 especially meaningful was not only the work itself, but the people. I spent time with the Mathagu brothers. They have managed the farm since 2018 when their father Walter passed away. What began as a side project for them has become a true family effort, and I had the chance to meet many of their children - another generation eager to learn, contribute, and eventually carry the farm forward.
Coming from a multi-generational coffee family myself, I feel a strong connection to this kind of long, evolving relationship. I’m grateful for the knowledge and perspective passed down to me by my father, and I recognize something familiar in how trust and understanding have been built at Mamuto.
2026 marks a meaningful milestone: twenty years for me at George Howell Coffee and twenty years of working with Mamuto. Two decades of collaboration, learning, and friendship.
We look forward to updating you as we continue this journey.
Sincerely,
Jenny Howell
