We love exploring the spectrum of flavors we can find in coffee… but sometimes, we come across flavors that are a little less palatable. One of the most unusual of these flavors is known as the Potato Taste Defect--PTD, or potato defect in short. While the potato defect itself is safe and won’t cause a person any illness, it can certainly make one turn their head because of the raw potato aroma and flavor it can cause in a coffee.
Coffees susceptible to PTD come from the area surrounding the African Great Lakes, including the countries Rwanda, Burundi, Democratic Republic of Congo, and Uganda. The potato flavor is caused by a member of the chemical family of pyrazines, commonly produced by plants. However, it still remains a mystery as to what causes coffee plants to produce this chemical. Research suggests that it is linked to a stink bug that feeds off of a coffee cherry. The broken cherry skin then becomes an entry point for a bacteria that causes the flavor defect.
Potato defect occurs on occasion, and luckily, it affects one bean instead of an entire coffee tree. That said, one bean can cause an entire batch of brewed coffee to taste unpleasant! Some roasters choose not to purchase coffees from countries that are prone to having potatoes, but well processed coffees from these regions can taste so delicious, we think the occasional potato is worth the risk. The defect occurs on the farm before the coffee is even processed, and there are people who are actively working towards finding a solution to eradicate this defect.
If you open up a bag of coffee and smell a hint of potato, don’t fret. It’s likely only one bean, and it won’t affect the flavor of the other beans in the bag. Grind your coffee in smaller doses so that you can find the potato, and throw it out--or brew it for fun! Whenever we come across it in our roastery or cafes, we let others in the building smell and taste the coffee. It’s a great learning opportunity for us, and serves as a reminder that producing a good cup of coffee is a lot of hard work!
To learn more about the potato taste defect and what folks are doing on the farm to address the issue, check out this article on Daily Coffee News: Potato Taste Defect: What Roasters Need to Know
