What does the coffee grading system in Kenya actually measure?

Kenya grades its coffee into eight classes: AA, AB, PB, C, E, TT, T, and MH/ML. The core criteria are bean size, shape, color, and density, with screen size and overall quality carrying the most weight. AA beans fall between 17 and 18 screen sizes and are known for strong density; AB is the next common grade seen on retail bags.

The system exists because coffee is an agricultural product whose quality varies from lot to lot, so grading creates uniform commercial lots and supports fair pricing. Types of coffee grown in Kenya include SL28, SL34, Batian, K7, and Ruiru11, all with relatively large beans. Exporters sometimes grade a second time, which is where labels like AA TOP come from.

Kenyan coffee is world-renowned for its clean, crisp, juice-like bright acidity. What exactly do the commonly seen labels in China such as "AA," "AB," and "AA TOP" represent? This article systematically sorts out Kenya's coffee bean grading system—from the specific classification criteria of the eight grades AA, AB, PB, E, C, TT, T, and MH/ML, to interpreting the characteristics of major varieties such as SL28 and SL34, and analyzing the commercial logic behind exporters' secondary grading. At the same time, it focuses on the Thika region, introducing the origin background and flavor performance of Front Street Kenya Small Tomato, an AA-grade K72 washed bean, along with detailed parameters and a three-pour method for high-concentration, high-extraction iced brewing.

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When it comes to coffee with prominent acidity, Kenya is often the first name that comes up. Coffee from this East African producing country is known for its clean, transparent mouthfeel and solid yet bright, juice-like acidity. In the domestic market, Kenyan labels such as "AA" or "AB" are commonplace, and some packages even say "AA TOP." What exactly do these letter combinations mean, and how big is the gap between them?

First, one thing must be made clear: coffee beans are essentially an agricultural product, so their quality inevitably varies. Precisely because of this, every coffee-producing country establishes a grading system to divide coffee beans into homogeneous commercial lots that meet established quality standards, thereby promoting the formation of a fair pricing mechanism.

Kenya is no exception. At present, the country's rating criteria include bean size, shape, color, and density, with the core indicators being bean size and overall quality. There are eight grades in total: AA, AB, PB, C, E, TT, T, and MH/ML, among which "AA" and "AB" are precisely the two levels most commonly encountered by domestic consumers.

The main coffee varieties grown in Kenya include SL28, SL34, Batian, K7, and Ruiru11. They share one common trait—relatively large beans. For this reason, in theory, the larger the bean, the better its quality performance.

AA-grade coffee beans fall between 17 and 18 screen sizes, with excellent density, and are regarded locally as representing high quality, with an elegant mouthfeel and rich flavor. AB grade falls between 16 and 17 screen sizes. Although its quality is not as good as AA, its price is more affordable, and since its output is the highest among all grades, accounting for about 40% of Kenya's total coffee, it enjoys very high market acceptance.

In addition, Kenya has two special grades classified by bean appearance. One is Peaberry (PB), a round green bean, in which the coffee fruit does not form the usual two flat beans but instead develops only a single round bean. The other is Elephant (E grade), formed when two coffee beans become intertwined during development, creating an unusually large single coffee bean that can reach 21 screen sizes or above. Both are abnormal bean types from atypical development. In Kenyan coffee, peaberry (PB) accounts for only about 5%, and elephant beans (E) are even rarer, so they circulate in small quantities on the market and command higher prices.

C-grade coffee beans fall between 12 and 14 screen sizes and are on the small side. TT grade consists of lightweight beans separated from E, AA, and AB grades using an airflow sorter, while T grade consists of defective beans picked out from C grade. Neither belongs to the specialty coffee category. MH/ML grade is regarded as low-quality coffee beans, usually mixed with unripe and overripe beans, so it is supplied only to the domestic market and not used for export.

However, bean size cannot directly determine whether flavor is good or bad. Therefore, some Kenyan exporters or green bean traders formulate their own grading standards and conduct a secondary assessment of exported coffee, mainly dividing it into "TOP," "Plus (+)," and "FAQ" based on cupping scores. It should be noted that this grading system has not received official Kenyan certification, and standards vary from merchant to merchant, so it can only serve as a reference; ultimately, one still has to look at the actual cupping performance of the coffee beans.

Looking back at history, Kenyan coffee was first introduced during the British colonial period. The colonial economy drove the development of the coffee industry and also enabled Kenya to establish a management system far more refined than that of many producing countries of the same period in areas such as selection and breeding, grading, and processing methods. Therefore, from the local perspective, reaching AA or AB grade is already considered to indicate excellent mouthfeel and flavor.

Front Street Kenya Small Tomato comes from the K72 washed processed coffee beans of the Asali Processing Plant in the Thika region, using the commonly seen Kenyan varieties SL28 and SL34, and is graded AA.

Thika is a small town under the jurisdiction of Nairobi, Kenya's capital. A large number of coffee fields are distributed around Nairobi. Thika itself is an industrial town, but it is surrounded by farmland and waterfalls. The area has about 2,000 coffee growers. The history of coffee cultivation in the Thika region can be traced back to the late 19th century, when coffee tree species were introduced from neighboring Ethiopia to the north. After local variety improvement, the four commonly seen varieties at present are Bourbon, Kents (SL34, SL28), Typica, and Ruiru 11. Today, about 90% of the planted varieties are SL34 and SL28. Through cupping, Front Street found that the flavor of this region presents bright fruit acidity, a thick berry juice sensation, and honey-like sweetness. The altitude range is between 1,550 and 1,750 meters.

Because this bean is plump and round, and also to fully bring out the solid, bright fruit acidity of Kenyan coffee, Front Street uses a light roast. After brewing, it presents the flavors of small tomato and smoked plum, with juice-like acidity and a clean, gentle mouthfeel.

Below, Front Street demonstrates the brewing process of a cup of iced Kenya Small Tomato coffee using a high-concentration, high-extraction method. The specific parameters and technique are as follows:

Dose: 15 grams

10x hot water: 150 grams

5x ice: 75 grams

Water temperature: 92°C

Grind size: 83% passing through a No. 20 sieve (EK43s setting 9, C40 setting 22)

Dripper: Hario V60

Technique: three-pour method

First, place 75g of ice cubes into the server, then pour 15g of ground coffee into the dripper and gently tap it level. For the first pour, use a small flow rate of 3 to 4 ml/s to pour 30g of hot water from the center outward in a small spiral, and let it bloom for 30 seconds; after 30 seconds, use the same technique to pour the second stage of 60g of water, being careful not to raise the water level too high, otherwise it can easily lead to underextraction; when the coffee liquid is about to finish draining, pour in all the remaining 60g of hot water at a flow rate of 3 ml/s, ensuring the total extraction time is controlled between 1 minute 50 seconds and 2 minutes.

After iced brewing, Front Street Kenya Small Tomato coffee shows rich berry notes. On the palate, it immediately offers the acidity of cherry tomato, smoked plum, and snow pear, accompanied by a faint caramel aftertaste. With the help of the ice cubes, the mouthfeel is especially fresh and crisp, leaving a deep impression.

The above content is compiled by CoffeeHunters, a coffee news website.