Silverskin

Silverskin is the thin, papery membrane (botanically the seed coat, or testa) that clings tightly to the surface of a coffee bean, including down in the center crease. It sits just inside the parchment layer, so it remains on the bean even after hulling removes the parchment.

Why it matters: during roasting, the silverskin dries out and loosens, then flakes off as the light, flyaway flakes roasters call chaff. Around and after first crack, most of it sheds, especially with washed coffees; some naturals and certain varieties hold onto more. Roasters collect this chaff in a tray or cyclone because too much buildup is a fire risk and can scorch the beans.

For most drinkers, silverskin is simply the brown flakes you see in a home roaster, a popcorn popper, or even occasionally in a bag of fresh beans. It is harmless. An optional milling step called polishing buffs off residual silverskin for a cleaner-looking green bean, though it makes little difference to flavor.