What are quakers in roasted coffee?

Quakers are unripe, underdeveloped coffee seeds that fail to roast properly - staying significantly lighter in colour than the surrounding beans after roasting. They're caused by unripe cherries making it through the processing and sorting chain and into the roast batch.

They're easy to spot: pale tan or cream-coloured beans standing out against the darker brown of properly developed coffee. They contribute peanut-like, papery, or bland flavours that can noticeably degrade the cup even at low numbers.

The primary prevention is at origin: selective harvesting of ripe cherry dramatically reduces quaker frequency. Float separation - which removes low-density beans including unripe ones - is also effective at the wet mill. In the roastery, quakers can be picked out by hand after roasting for high-quality specialty lots. The SCA's roasted coffee standard considers more than three quakers per 100 grams an indication of a substandard lot.