When we buy coffee we can see a number of things on the packet. Information will often include the country the beans originated from, the farm they came from and then additional terms that relate to the quality. We will try here to make sense of what the sizing of the coffee bean means.
Coffee sizes are called ‘grades’. The size of a coffee bean is important as there is a correlation between the size of a bean and its quality. Whilst others factors will affect taste, all things being equal, a larger coffee bean should produce a better tasting brew than a small bean.
What further confuses the consumer is that different countries use the word ‘grading’ differently. The Speciality Coffee Association of America for examples uses the word grading to consider more than just size. Other countries use grading to describe the elevation of the bean. So do beware.
Consistency of Size
What matters to roasters is that within a bag the beans are of a consistent size. Larger beans roast more slowly than smaller beans so you don’t get a consistent roast of the beans if they are of different sizes. To ensure this consistency beans are sifted through screens which are metal sheets with holes punched in them of a certain size. This prevents beans of different sizes being put together.
Numbering System Used
The metal screens are numbered 8 through to 20. These numbers refer to how many 64ths of an inch the holes are. So a size 9 screen has holes that are 9/64 inch wide. What you will find is that even numbered screens tend to be used for Arabica selections and odd numbered screens are for Robustas. It is important to note that this system is not perfect so variances are allowed.
A further complication is that sorting happens in different countries so local terminology will come in. An example is a screen size 20 bean will have an industry classification of ‘very large’, in Africa and India the term that will be used for these beans is ‘elephants’. These beans are actually the exception to the rule that big beans are the best. They often break up during roasting.
To further show the different terminology used let’s take screen size 16. The industry classification for this is ‘large’, in Central and South America the term used is Segundas, in Columbia Excelso and Africa and India the term is AB.
Most roasters look for coffee that is screen size 16-18. These tend to be of a superior quality. Anything smaller than 14 tends to be used for cheaper coffees.
Superior, Supremo, AA
These are terms you may see on packaging. AA refers to a larger than normal bean. Kenyan AA coffee beans for example are grade 18 in size. If you see AA on a packaging it will usually relate to really good quality beans.
Supremo is used in Columbia. They pass through size 18 and are seen to reflect a quality coffee bean. Excelso, is also used in Columbia, these beans are slightly smaller than Supremo but pass through size 16 sieve perforations. In summary all of these terms suggest a quality coffee bean.