How Does the Kenyan Coffee Grading System Work?

Kenya's coffee grading system sorts beans by size after milling, using letters such as AA, AB, and PB. AA is the largest size class, AB covers a middle screen range, and PB stands for peaberry, the round single bean that forms when only one seed develops inside a cherry. Grade reflects size, not cup quality by itself.

The bright acidity that defines Kenyan coffee comes from growing conditions rather than the grade letters. The coffee belt sits in volcanic soil at 1,600 to 2,100 meters, where slower cherry ripening lets aromatic compounds accumulate. Kenya has two rainy seasons and harvests from October to December and June to August. Main coffee producing regions include Nyeri, Murang'a, and Kirinyaga.

Kenyan coffee is known for its clean and refreshing taste and bright fruit acidity, making it one of the most recognizable African beans in the minds of many coffee lovers. Why is Kenyan coffee so acidic? This is inseparable from its high-altitude growing environment, volcanic soil, and unique washed processing method. This article will systematically sort out the growing conditions and historical context of Kenyan coffee, introduce the ten major producing regions one by one, including Nyeri, Murang’a, Kirinyaga, explain in detail the official grading standards such as AA, AB, and PB based on bean size, and analyze the causes of its signature acidity. At the end, Front Street Coffee’s pour-over parameters for Kenya Asaliya are shared for practical reference.

Many friends who are new to specialty coffee, after discovering that coffee can actually be acidic, often ask one more question: which coffee has the most prominent acidity? Faced with this question, Front Street’s baristas almost always blurt out—Kenya. The characteristics of Kenyan coffee lie in its clean and refreshing taste, full and solid body, and bright, uplifting fruit acidity. Almost anyone who has tried it is deeply attracted by it.

Coffee Growing Conditions

Kenya is located in East Africa, with the equator passing through its center and the East African Rift Valley running north to south. The country has extensive highlands, with an average altitude of about 1,500 meters. Mount Kirinyaga, the second-highest peak in Africa, also known as Mount Kenya, reaches 5,199 meters, and its summit is covered with snow year-round.

As a tropical producing region, Kenya has two rainy seasons a year, with corresponding harvest periods from October to December and June to August. Kenya’s coffee-growing belt is mainly located in volcanic soil areas at altitudes of 1,600 to 2,100 meters. Due to the high altitude, the ripening cycle of coffee cherries is extended, allowing aromatic substances to fully accumulate within the beans, resulting in prominent fruit acidity and relatively hard beans.

Coffee Growing History

Although neighboring Ethiopia is recognized as the birthplace of coffee, Kenya’s history of coffee cultivation did not begin until the end of the 19th century. In 1893, missionaries introduced the Bourbon variety from Brazil to Kenya. In 1895, Britain colonized Kenya, designated it as the "East Africa Protectorate," and took control of all crops, including coffee.

Between 1900 and 1933, the colonial government established the Coffee Board (CB), responsible for licensing, inspection, and promotion of coffee. In 1934, auctions became one of the sales methods for Kenyan coffee, while the first coffee auction was not held until September 1935. In 1946, the Coffee Marketing Board (CMB) was established and officially became fully operational on July 1, 1947, but the agency was abolished in 1971.

Introduction to Kenya’s Coffee Producing Regions

There are mainly 10 coffee-producing regions in Kenya: Nyeri, Murang’a, Kirinyaga, Embu, Meru, Kiambu, Machakos, Nakuru, and Kisii.

[Nyeri/Nyeri]

The Nyeri producing region is located in central Kenya and is home to Mount Kenya, an extinct volcano. The fertile volcanic red soil provides unique conditions for producing Kenya’s top coffee. The region is dominated by cooperatives formed by smallholder farmers, while large estates are relatively rare. The growing altitude ranges from 1,200 to 2,300 meters.

[Murang’a]

The Murang’a producing region is under the jurisdiction of Central Province, with about 100,000 coffee growers in the area. This was one of the earliest areas where missionaries chose to settle. Murang’a also has fertile volcanic soil, and the number of smallholder coffee farmers exceeds that of estates. The growing altitude ranges from 1,350 to 1,940 meters.

[Kirinyaga]

The Kirinyaga producing region is located east of Nyeri, and its volcanic soil is equally fertile. Coffee produced by smallholder farmers is more common in this region, and local processing plants also produce many coffees of excellent quality. The growing altitude ranges from 1,300 to 1,900 meters.

[Embu]

The Embu producing region is adjacent to Mount Kenya, and its name comes from Embu town. About 70% of the local population is engaged in small-scale farming, and almost all coffee beans come from smallholder farmers, with overall production relatively low. The growing altitude ranges from 1,300 to 1,900 meters.

[Meru]

Coffee in the Meru producing region is mostly grown by smallholder farmers on the slopes of Mount Kenya and the Nyambene Hills. The name Meru comes from the local Meru people. In the 1930s, they became the earliest Kenyans to engage in coffee production, thanks to the Devonshire White Paper signed in 1923, which safeguarded the rights of Kenyan Africans. The growing altitude ranges from 1,300 to 1,950 meters.

[Kiambu]

The Kiambu producing region is located in central Kenya and is dominated by large coffee estates. However, with the advancement of urbanization, the number of estates has decreased. Coffee from Kiambu is usually sold under sub-region names, such as Thika, Ruiru, and Limuru. There are also a considerable number of smallholder farmers in the area. The growing altitude ranges from 1,500 to 2,200 meters.

[Machakos]

Machakos is a relatively small county in central Kenya, and the producing region is named after Machako town. Coffee production here is made up of both estates and smallholder farmers. The growing altitude ranges from 1,400 to 1,850 meters.

[Nakuru]

The Nakuru producing region is located in central Kenya and has the highest-altitude coffee-growing areas among the central producing regions. This is because some high-altitude plants stop growing due to dieback. The producing region is named after Nakuru town. The growing altitude ranges from 1,850 to 2,200 meters.

[Kisii]

The Kisii producing region is located in the southwest of Kenya’s coffee-producing areas, near Lake Victoria, and is relatively small. Coffee in the area is mostly produced by cooperatives formed by independent small producers. The growing altitude ranges from 1,450 to 1,800 meters.

Kenya’s Coffee Grading System

Friends who have followed Front Street’s content on Kenyan coffee can easily notice the existence of Kenya AA. Kenya developed its coffee economy during the colonial period, and the entire system leaned toward refined management. Its level in breeding, grading, and processing methods far exceeded that of many coffee-producing countries at the time. It was not until decades later, when other countries also recognized the advantages of refined management and followed suit, that Kenya’s standout position gradually changed.

1. Distinguished by size, shape, and weight

E: elephant bean, above screen 18 (including round beans), includes large round beans; like PB, relatively small in quantity

AA: screen 17-18

AB: screen 15-16, a mixture of Grade A and Grade B; above screen 17 (6.8 mm) is Grade A, and above screen 16 (6.3 mm) is Grade B

TT: light beans screened out from AA and AB by an air separator

PB: above screen 15, round beans, peaberry, accounting for about 10% of Kenyan coffee

C: screen 12-14, as well as light beans screened out from PB by an air separator

T: below screen 12, with more defective beans, broken beans, and light beans

HE: grades outside the above become HE (Hulled Ears)

2. Raw beans that have not undergone official standard grading are UG (ungrade)

E, AA, AB, PB→UG1

C, TT, T, HE→UG2

3. MBUNI (natural beans, non-washed processing)

All raw beans undergo gravity separator sorting

MH: heavy mbuni, heavy beans, yellow, no black beans, fragments, dried fruit, or other defects; cup profile shows typical natural processing flavor, with no flavor defects

ML: light mbuni, yellow-green, with a small amount of insect-damaged beans or black beans, no stinker beans or fragments, and no earthy taste or other bad flavors in the cup

The above is Kenya’s official national grading system. In addition, Kenyan exporters or green coffee traders have added special grading for AA-grade and AB-grade green coffee beans (not officially recognized by the Kenyan state), in order as TOP, PLUS (+), FAQ

Reasons for the Taste Characteristics of Kenyan Coffee

The fermentation time of Central and South American beans in washing tanks usually does not exceed 36 hours, while Kenyan washed fermentation lasts as long as 72 hours. After 30 to 48 hours of fermentation, parchment beans are removed from the tank. At this point, the mucilage on the bean surface has basically been removed, but they still need to be soaked in clean water for 24 hours. After cupping many beans, Front Street observed that this additional fermentation process should be closely related to the bright and clean flavor of Kenyan AA-grade coffee.

How to Drink Kenyan Coffee

Take FrontStreet Coffee Kenya Asaliya as an example:

FrontStreet Coffee: Kenya·Asaliya Coffee Beans

Producing region: Asali processing plant, Thika producing region, Kenya

Altitude: 1,550 meters—1,750 meters

Variety: SL28, SL34

Processing method: K72 washed processing

Flavor description: smoked plum, cherry tomato, snow pear, yellow sugar, plum

FrontStreet Coffee Pour-Over Parameters Sharing

Dripper: Hario V60

Dose: 15 grams

Coffee-to-water ratio: 1:15

Water temperature: 90℃

Grind size: EK43s#10 (80% passing through No. 20 standard sieve)

Pour 30 grams of water in the first stage for a 30-second bloom, then pour in the second stage up to 125 grams for staging. When the water level drops to the point where the coffee bed is about to be exposed, pour in the third stage until 225 grams and stop pouring. Wait for the water in the dripper to completely drip into the server, then remove the dripper. Total extraction time 2'00".

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