Rwanda’s ‘Specialty Coffee’ Under Attack by Stink Bugs

Rwanda is gaining a worldwide reputation for its bourbon and other specialty coffee, a crop grown in the country’s rich volcanic soils. Specialty coffee comprises almost one-third of Rwanda’s agricultural exports. But a sizable portion of the crop is being compromised by a defect called “potato taste.” There is growing evidence that potato taste may be in part caused by the antestia, or “stink bug.”

At the beginning of January, University of California entomologist Thomas Miller joined a team of Rwandan researchers to examine the causes and impacts of potato taste, and its possible connection to the antestia bug. Cathy Majtenyi asked Professor Miller more about his research trip.

 

MAJTENYI: “Describe what is meant by specialty coffee.”

MILLER: “Ordinary coffee does not have any taste qualifications, but specialty coffee is very much like the wine industry: the taste and smell and odor is everything. And they have strict standards that they use to judge the quality of the coffee crop. Usually the bourbon variety of arabica coffee is the one that they use for that. Specialty coffees usually are determined by the buyers. They are based on this very strict, what they call “cupping” taste process. Specialty coffee has very high standards, and in fact it is very common to lose upwards of a third or a fourth of the crop because it does not meet the standards.”

MAJTENYI: “Potato taste” has been defined as a defect that compromises the quality of coffee and is threatening to deter international buyers from purchasing Rwandan coffee. Tell me more about potato taste and what causes this defect.”

MILLER: “Potato taste is something that the tasters come up with. For want of a better word, they have dozens and dozens of characteristic potato flavors: walnut, berry, cedar, a whole bunch of them. To me, it tastes like old toenails. It has to do with the subtle aroma and taste of the coffee. For some reason, potato taste is peculiar to this East African area. It may have something to do with the volcanic soil. It may have something to do with the insect complex that is unique here. The exact cause of potato taste is not really known because there are so many elements that go into the final taste of coffee.

MAJTENYI: “You and your team were in Rwanda under the auspices of the Global Knowledge Initiative. You indicated that you wanted to learn more about potato taste and its possible connection with the antestia bug. What are you doing with the knowledge that you gained?”

MILLER: “Global Knowledge Initiative hopes at the end of this process to put in place the steps necessary to address the potato taste problem broadly. They asked me to participate because I am giving them advice on how to include work on the bug, because there is a loose association between potato taste and the bug.  We are collecting biological samples in collaboration with the industry here and the university (National University of Rwanda). We are designing approaches to put together teams to address the issue. My purpose is to help them collaborate and connect with other people in the world who can weigh in on this problem.”