Quaker
also: quaker bean
An underripe bean that fails to brown in roasting and tastes papery, peanutty, or cereal-like.
A quaker is a bean that was picked underripe and lacks the sugars needed to brown properly during roasting. When you roast a batch, quakers stay pale and yellowish-tan while everything around them turns brown, so they are easy to spot in light against a dark background. They are a recognized defect.
Why it matters: quakers do not just look wrong, they taste wrong. Without enough sugar to caramelize, they bring papery, peanutty, cardboard, or stale-cereal flavors that dull and flatten the cup. A few in a brew can mute sweetness and clarity; many will noticeably degrade it.
They are most common in natural process coffees, where underripe cherries are harder to spot and remove before drying, and in machine-harvested lots. Because they only reveal themselves after roasting, the usual fix is hand sorting the roasted beans on a tray and picking out the pale ones, a routine step for careful roasters and a worthwhile habit for home roasters. In grading, related issues are counted under the defect system.