Coffee: Production, Quality and Chemistry
CHAPTER 17: Coffee Certification
Published:11 Jan 2019
Although coffee grading may refer to different things and concepts, in this chapter it is understood as defect removal and bean sizing in order to refine the natural quality of the coffee lot and to bring it to standards demanded by different markets. This type of grading is performed in three stages – cleaning, sizing, and sorting of defects, usually carried out in this order. Cleaning is undertaken by two machines – precleaners and destoners – that are usually equipped with magnets, sizing by graders with screens of different sizes and shapes, and defect removal by densimetric separators and color sorters that take out beans with low density and unwanted colors, respectively. Different markets require different bean size distributions and defect contents that are associated with appearance and, most importantly, quality. Bean size affects the aspect of coffee more than its cup quality that is related with the number and type of defects found in it as well as by processing, climate, variety, etc. Some countries have established export types or qualities associated mostly with bean size and defect count, e.g.: Colombia Supremo and Kenya AA. Other countries have this grading system also linked to cup quality and deliver mostly to clients’ requirements, for example, Brazil. The usual practice by roasters and soluble makers is to use coffees from different origins and qualities to make their own blends, with single-origin coffees still representing a very small part of the market in importing countries.