Grading and sorting are done by size and weight. Coffee cherries are also reviewed for color flaws or other imperfections. Beans are separated by being passed through a series of screens with graduated hole sizing. By using vibrating air table, employing gravity, they are sorted automatically by density and to isolate defective (e.g., hollow or nicked) coffee beans, which can harm the taste of the final product.
Typically, the bean size is represented on a scale of 10 to 20. The number represents the size of a round hole diameter.
Finally, defective beans are removed either by hand or by machinery. Beans that are unsatisfactory due to deficiencies (unacceptable size or color, over-fermented beans, insect-damaged, unhulled) are removed. This process could be done both by machine and by hand, ensuring that only the finest quality coffee beans are packed.
Grade AA: Specialty Grade Coffee Beans
This is the highest grade of beans, and to be classified as Grade AA Coffee. The beans need to have no primary defects and 0-3 full defects, with a maximum of 5% above and below the specified screen size. When cupping, these beans need to have a distinct attribute in one of the areas of taste, acidity, body or aroma, and be free of cup faults and taints. These beans also need to have zero of what is referred to as “Quakers” which are unripe or poorly roasted beans.
Grade A: Premium Grade Coffee Beans
The second highest grade, and the one you most often would be drinking, these beans are the same as Grade AA coffee beans, but are allowed a maximum of 3 Quakers and 0-8 defects.
Grade AB: Exchange Grade Coffee Beans
These beans will have 50% above screen 15 and 5% below it, with a maximum of 5 Quakers, free from faults, but between 9-23 full defects are permissible. Supermarket brands are using these beans.
Grade B: Standard Grade Coffee Beans
These will have 24 to 86 full defects per 300g.
Grade Y: Off Grade Coffee Beans
These beans have more than 86 full defects per 300g, often used in the instant coffee industry.