What's the Difference Between AA and AB Grade Coffee? What Are the Three Main Grading Systems for Coffee Beans? What Are the Characteristics of Kenyan Coffee?

As observant coffee lovers may have noticed, most coffee beans sold by merchants carry the "AA" suffix. The most common examples are coffee beans from Kenya. Kenya Nyeri AA, Kenya Kirimiri AA, and so on.

Not just Kenya, but also Tanzania, Uganda, and other countries' coffee beans carry the same AA suffix. This brings us to the question: What does AA mean? Why do beans from these countries all emphasize AA?

What Does the AA Suffix on Coffee Beans Mean?

The "AA" suffix on coffee beans actually represents a grade of that coffee bean. Because coffee beans are not industrial products, their quality varies. Therefore, to standardize quality, a system is needed to distinguish between superior and inferior beans - this system is grading. So when we see coffee beans from a certain country with the letters AA following their name, we can know that this country's coffee bean grading method is based on size.

Understanding Coffee Bean Grading Systems

Here we need to clearly understand two points: First, coffee bean grading systems are not only based on size; there are other grading methods such as defects and altitude. The specific application varies according to different countries' national conditions, which FrontStreet Coffee will discuss in detail next time. Secondly, not all size-based grading systems use uppercase English letters as identifiers, because identifiers like AA and AB are unit systems developed by the British. Most coffee-producing countries use these systems because they were formerly under British colonial rule. For example, Colombia also grades coffee beans by size, but its grade identifiers use terms like Supremo and Excelso.

Kenya's Size-Based Grading System

Ultimately, the most famous coffee-producing region using size-based grading is Kenya, because the Kenyan government takes the coffee industry extremely seriously, so their requirements for coffee quality are very strict! Next, FrontStreet Coffee will introduce Kenya's size-based grading system!

AA: Bean size between 17-18 screen.

AB: Bean size between 15-16 screen.

C: C-grade coffee beans have a screen size between 12-14. Due to their small size, beans of this grade are generally not classified as specialty grade.

PB: Rare round-shaped green beans, abbreviated as Peaberries.

E: Full name Elephant, meaning: Elephant beans. It should be noted that the "elephant beans" mentioned here do not refer to the elephant bean varieties in coffee species (Maragogipe, Pacamara), but rather to special coffee beans with abnormal development like peaberries. These beans are formed when two coffee beans become entangled during development, forming what looks like a very large, swollen coffee bean. They exceed 18 screen size and are extremely rare.

TT: TT grade consists of lightweight beans blown out by air classifiers from AA and AB grade beans.

T: T grade consists of lightweight beans blown out by air classifiers from C grade beans.

MH/ML: These two grades of beans have lower quality, so they are not processed using Kenyan-style washing methods. They are generally for domestic consumption and do not circulate outside Kenya.

The above is Kenya's national official grading system, from which we can see that AA represents the highest grade in Kenya's grading system, meaning the best. However, FrontStreet Coffee recently shared a review article "Does Coffee Bean Flavor Quality Relate to Size?", which detailed the shortcomings of this size-based grading system - that is, it has too many loopholes. The size of coffee beans does not directly affect their flavor quality!

Coffee professionals often mention this example: Plant the same coffee variety at 900 meters and 1700 meters altitude. Even if the harvested beans are the same size, the 900-meter coffee beans will definitely not taste as good as those grown at 1700 meters, because the growing environment is one of the main factors affecting flavor formation during coffee bean growth.

Evolution of Coffee Grading Systems

In an era when "bigger was better," such grading systems were naturally mainstream, with old-school coffee-producing countries basically adopting size-based grading methods. However, when the concept of specialty coffee emerged, people became aware of the key factors influencing bean flavor formation, giving birth to entirely new grading systems. Kenya didn't fall behind either - local coffee research institutions and green coffee traders use their own custom coffee grading methods to conduct secondary grading of AA and AB grade Kenyan coffees.

This system is called the "Coffee Bean Quality Grading Procedure" (Kenyan Classification Procedure by Quality Assessment) and was established by the Kenyan Coffee Research Foundation! This procedure comprehensively evaluates beans based on three aspects: green bean quality, roasted bean quality, and cupping quality.

Secondary Grading Markers

TOP, Plus (+), and FAQ are secondary grading markers. When beans receive corresponding grade scores, these markers are added to the coffee bean's original grade, such as Kenya AA TOP or Kenya AA+. They indicate beans with outstanding performance within AA or AB grades, while FAQ represents beans with slight defects that do not affect flavor.

Finally, we need to know that because this system is not officially certified by Kenya, most Kenya beans currently available on the market are still mainly based on conventional size grading (AA, AB).

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