Why is Kenyan Coffee So Acidic? Understanding Kenya AA, AB, PB Grade Classifications and Regional Flavor Profiles

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When beginners in specialty coffee learn that coffee can actually be acidic, they naturally ask, "What is the most acidic type of coffee?" When faced with this question, FrontStreet Coffee's baristas immediately think of Kenyan coffee. Kenyan coffee is characterized by its clean, refreshing taste, substantial mouthfeel, and bright fruit acidity. Anyone who has tried Kenyan coffee has been captivated by its charm.

Coffee Growing Conditions

Kenya is located in East Africa, with the equator running through its central region and the East African Rift Valley stretching from north to south. Kenya's terrain is predominantly highland, with an average altitude of 1,500 meters. Mount Kirinyaga (Mount Kenya), Africa's second-highest peak, stands at 5,199 meters with year-round snow cover on its summit.

Kenya is situated in tropical growing regions with two rainy seasons annually, resulting in harvest periods from October to December and June to August. Kenya's coffee-growing areas are mainly distributed in volcanic regions at altitudes between 1,600 and 2,100 meters. Due to the suitable growing altitude, coffee cherries require extended time to mature, allowing full absorption of aromatic components into the coffee beans, resulting in prominent fruit acidity and harder bean density.

Coffee Growing History

Kenya's neighboring country, Ethiopia, is renowned as the "birthplace of coffee," but Kenya's coffee cultivation history can only be traced back to the late 19th century. In 1893, missionaries introduced Bourbon varieties from Brazil to Kenya. In 1895, Britain colonized Kenya, incorporating it into the "East Africa Protectorate" and controlling all agricultural crops in the country, including coffee.

Between 1900 and 1933, the colonial government established the Coffee Board (CB), which was responsible for coffee licensing, inspection, and promotion. In 1934, auctions began as a method for selling Kenyan coffee, though the first coffee auction wasn't held until September 1935. The Coffee Marketing Board (CMB) was established in 1946 and began full operations on July 1, 1947, but was abolished in 1971.

Kenyan Coffee Growing Regions

Kenya has ten main coffee-growing regions: Nyeri, Murang'a, Kirinyaga, Embu, Meru, Kiambu, Machakos, Nakuru, and Kisii.

Nyeri

The Nyeri region is located in central Kenya, home to Mount Kenya's extinct volcano. It boasts fertile volcanic red soil, providing excellent conditions for producing Kenya's finest coffee. In this region, smallholder cooperatives are more common than large estates. The growing altitude in this area ranges from 1,200 to 2,300 meters.

Murang'a

The Murang'a region belongs to the Central Province and has approximately 100,000 coffee farmers. It was among the first areas where missionaries chose to settle. This region also has fertile volcanic soil, with more smallholder coffee farmers than estates. The growing altitude here ranges from 1,350 to 1,940 meters.

Kirinyaga

The Kirinyaga region is located east of the Nyeri region and also features fertile volcanic soil. In this region, coffee from smallholders is common, and processing plants also produce many excellent quality coffees. This region's growing altitude ranges from 1,300 to 1,900 meters.

Embu

This region is near Mount Kenya, and the Embu region gets its name from Embu city. Approximately 70% of the local population in Embu engages in small-scale agriculture, but almost all coffee beans come from smallholder farmers, resulting in relatively low production. The Embu region's growing altitude ranges from 1,300 to 1,900 meters.

Meru

Most coffee in the Meru region is grown by smallholder farmers on the slopes of Mount Kenya and the Nyambene Hills. The name Meru comes from the people of this region, the Meru people. In the 1930s, they were among the first Kenyans to produce coffee, thanks to the Devonshire White Paper signed in 1923, which guaranteed the importance of rights for African people in Kenya. The Meru region's growing altitude ranges from 1,300 to 1,950 meters.

Kiambu

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

Machakos

The Machakos region is a relatively small county located in central Kenya. The Machakos region gets its name from Machakos town. Coffee production in this region includes both estates and smallholder farmers. The growing altitude in this region ranges from 1,400 to 1,850 meters.

Nakuru

The Nakuru region is located in central Kenya's growing areas and features the highest altitude coffee cultivation within the central region. Due to certain coffee plants growing at high altitudes being affected by dieback disease and ceasing growth, some areas face challenges. The Nakuru region gets its name from Nakuru town. The growing altitude in this region ranges from 1,850 to 2,200 meters.

Kisii

The Kisii region is located in the southwestern part of Kenya's coffee-growing areas, near Lake Victoria, and is relatively small in area. Most coffee in this region comes from cooperatives formed by independent small-scale producers. The growing altitude in this region ranges from 1,450 to 1,800 meters.

Kenyan Coffee Grading System

Those who have read FrontStreet Coffee's articles about Kenyan coffee will undoubtedly notice the mention of Kenya AA. During its colonial period, Kenya developed its coffee economy with the entire system leaning toward refined management. Kenya's coffee breeding, grading, and processing methods were far ahead of many coffee-producing countries at that time. It wasn't until decades later that other countries recognized the advantages of this refined management and began to emulate it, gradually diminishing Kenya's unique position.

1. Classification by particle size, shape, and weight:

E: Elephant bean, 18 mesh and above (including round beans), containing large round beans, similar to PB but in smaller quantities

AA: 17-18 mesh

AB: 15-16 mesh, a mixture of A and B grades, with beans 17 mesh (6.8mm) and above classified as A grade, and 16 mesh (6.3mm) and above as B grade

TT: Light beans screened from AA and AB using an air classifier

PB: 15 mesh and above, round beans (peaberry), accounting for approximately 10% of Kenyan coffee

C: 12-14 mesh, and light beans screened from PB using an air classifier

T: Below 12 mesh, containing more defective beans, broken beans, and light beans

HE: Beans outside the above grades are classified as HE (Hulled Ears)

2. Unprocessed green beans not officially graded are classified as UG (ungraded):

E, AA, AB, PB → UG1

C, TT, T, HE → UG2

3. MBUNI (sun-dried beans, non-washed processing):

All green beans undergo gravity separation

MH: Heavy mbuni, yellow beans, no black beans, broken pieces, dried fruit, or other defects, typical sun-dried flavor in cupping, no taste defects

ML: Light mbuni, yellow-green, with some insect-damaged or black beans, no musty beans or broken pieces, no earthy or other bad flavors in cupping

The above is Kenya's national official grading system. Additionally, Kenyan exporters or green bean traders have introduced special grading (not officially recognized by Kenya) for AA and AB grade coffee beans, in order of TOP, PLUS (+), and FAQ.

Reasons for Kenyan Coffee's Flavor Characteristics

Beans from Central and South America rarely ferment in washing tanks for more than 36 hours, but Kenyan washing periods last up to 72 hours. After fermenting for 30-48 hours, the coffee in parchment is removed from the washing tank. At this point, the mucilage on the bean surface has been completely removed, but it still requires 24 hours of soaking in clean water. After cupping multiple beans, FrontStreet Coffee found that this additional fermentation step should be related to the bright, clean flavor characteristics of Kenya AA coffee.

How to Brew Kenyan Coffee

Taking FrontStreet Coffee's Kenya Asalia as an example:

FrontStreet Coffee: Kenya · Asalia Coffee Beans

Region: Asali Processing Station, Thika Region, Kenya

Altitude: 1,550 - 1,750 meters

Varieties: SL28, SL34

Processing: K72 Washed Processing

Flavor Notes: Black plum, cherry tomato, snow pear, brown sugar, plum

FrontStreet Coffee's Pour-Over Parameters:

Dripper: Hario V60

Dose: 15 grams

Ratio: 1:15

Temperature: 90°C

Grind: EK43s #10 (80% pass-through on #20 standard sieve)

First pour 30 grams of water for a 30-second bloom, followed by a second pour to 125 grams. When the water level drops to just before exposing the coffee bed, perform the third pour to 225 grams and stop pouring. Wait until all water has dripped through the filter into the serving pot before removing the filter. Total extraction time is 2'00".

Important Notice :

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