Quakers are defective coffee beans that fail to roast properly, remaining stubbornly light-coloured. In the classification of coffee according to the SCAA (Specialty Coffee Association of America, the standard classification system), quakers are listed as important defects :

In the Specialty Grade no quakers are permitted in 300 grams of beans. In the Premium Grade only 3 quakers are permitted and in the Exchange Grade 5 quakers are permitted in 300 grams

Quakers can have a strong influence on the coffee's flavour profile, imparting a spoiled taste to the brew.