Coffee grading is used to get a measure of the quality of a batch of coffee beans. However, the names of the grade and the specific requirements for grading vary, including some companies that have classification standards unique to them. It is because of this that determining the specific standards the source of the coffee been uses for its grading is important to know, For most customers, the grade of the coffee they purchase will not matter a great deal as the coffee available is generally going to be decent.
Step one in the grading process is sifting and sorting the beans. A sample of unroasted coffee beans are sorted by size using screens or containers with multiple layers of different sized holes.
These holes allow certain sizes of bean through and keep others based on their size. Higher quality batches of beans will have a more uniform size, allowing a more even roast, with the best coffee grades having a maximum of 5% above and 5% below the main screen size, which is determined by weighing the beans in each screen.
To sort the beans, a sample is taken from the lot and they are inspected carefully for defects. Defects can include large rocks, shells and under ripened beans. Higher grades of coffee will have fewer defects than lower grade coffees. Some grading standards only grade on the size, number of defects and moisture content of the coffee and would stop here.
After sorting and sifting, the beans are roasted and cupped. Roasting is done by slowly drying out and heating the coffee bean to specific temperatures to achieve the right level of darkness.
Cupping allows the flavor and characteristics of the coffee to be evaluated. The graders are looking for the taste and aroma of the coffee, in addition to its body, acidity, and other characteristics. To cup coffee, a sample of beans is ground, then hot water is poured over them. After 3-4 minutes the crust, formed from the coffee grind and foam at the top of the cup, is broken and smelled to sample the aroma of the coffee. Two spoons are then used to remove the crust from the cup, leaving as much of the liquid behind as possible.
At this point, the taster uses a spoon to get some coffee out of the cup and slurp it. Slurping allows the coffee to aerate and spray over the tongue, making it easier to taste. After tasting, the coffee is either spit into a cup or swallowed. This process is very similar to wine tasting and the same cup may be tasted multiple times as it cools as the temperature will change the flavor.The Specialty Coffee Association has specific standards for how cupping should be done for grading.
Once the grading process is complete the coffee is given a final grade. These vary but will generally contain a specialty or extra-fine grade at the top and about 5 grades to assign.