It is estimated that the consumption of special coffees in 2015 will be superior to 10 million bags (60Kg), representing approximately 28 billion cups and, in the consumer market, the importance of US$144 billion/year. According to the Specialty Coffee Association of America (SCAA), one sample of roasted coffee is classified as special when it presents, among other criteria, the absence of unripe beans that do not develop during the roasting, namely the Quaker. The greater incidence of Quaker is associated to the production of natural coffees due to the inefficiency of the available current technologies. However, it is frequent to find natural coffees sold as special containing variable amounts of Quaker, thus leading one to question if the criteria adopted by SCAA are valid. Furthermore, there are no scientific evidences that prove the impact of such beans over the sensory quality, as well as about the threshold of its perception. Thus, we aimed to assess this threshold and possible impacts of Quaker on special coffee through adaptations on the SCAA protocol. The study was conducted using natural Arabic coffee produced in Brazil. To assess the presence and impacts of Quaker three categories of beans were created following the Agtron color system. For the category A(#61.2) 0-30 beans/cup were used, while for B(#80.4) and C(#95.4) 0-16 beans/cup. The sensory assessment was performed by five tasters with certification Q-Grader with three repetitions per treatment (Category x Concentration). Adaptations were made on the sensory evaluation form to provide a better description of attributes. It was observed that the categories B and C had a significant influence on the quality of natural special coffee, thus providing a sharp flavor of unripe coffee. The perception of harmful effects was evident from 13 beans/cup (category C), thus influencing directly the global grade, sweetness, astringency and completion.