What does “chaff” refer to in coffee?

"Chaff" refers specifically to the outer skin that flakes off during the roasting process of coffee beans. As coffee beans are roasted, they undergo various physical and chemical changes, one of which includes the loosening of this outer layer. When the beans are roasted, the heat causes the chaff to separate from the bean, resulting in a light, papery coating that can be seen around the roasted beans.

This detachment is a normal part of the roasting process, and the chaff is typically removed during the post-roasting phase to ensure a clean and high-quality product. Understanding what chaff is and its role in this process helps in recognizing the importance of cleanliness in coffee processing and the characteristics of the final roasted product.