The Difference Between Kenyan Coffee Beans AB and AA Grade: The Relationship Between Kenyan Coffee Grading and Coffee Bean Prices

Introduction to Kenyan Coffee

When it comes to African coffee beans, most people immediately think of either Ethiopian or Kenyan coffee. Ethiopian coffee beans offer fresh, clean acidity, while Kenyan coffee is known for its rich berry fruit juice, such as tomato juice notes and plum acidity that leave a lasting impression. Many coffee enthusiasts ask FrontStreet Coffee's baristas: What is Kenyan AA?

Kenyan AA is a grading system for coffee beans in Kenya. Now, follow FrontStreet Coffee as we explore Kenya as a country, understanding Kenyan coffee through its growing regions, varieties, FrontStreet Coffee's roasting approach, cupping, and brewing methods.

Kenyan Coffee Growing Regions

Kenya is located in eastern Africa, with the equator crossing through its central region and the East African Rift Valley running north to south. It borders Somalia to the east, Tanzania to the south, Uganda to the west, and Ethiopia and Sudan to the north, with the Indian Ocean to the southeast. The country is predominantly highland, with an average elevation of 1,500 meters. Mount Kirinyaga (Mount Kenya) in central Kenya reaches 5,199 meters and has snow-covered peaks, making it Africa's second-highest mountain.

Kenya's coffee growing regions are most famous for seven main areas: Thika, Kirinyaga, Mt. Kenya West, Nyeri, Kiambu, Ruiri, and Muranga. The foothills of Mt. Kenya and the Aberdare Range are the primary growing areas. Specialty coffee regions mainly include Thika, Nyeri, Kirinyaga, and Muranga.

Nyeri Region

Located in central Kenya, Nyeri is home to the dormant volcano Mount Kenya. The region's red volcanic soil nurtures Kenya's finest coffee. Agriculture is extremely important in this area, with coffee being the primary crop. The Nyeri region has more smallholder cooperatives than large estates. Elevation: 1,200 to 2,300 meters. Harvest period: October to December (main season) and June to August (secondary season).

Muranga Region

Belonging to the Central Province, this region has approximately 100,000 coffee farmers. This inland region was one of the first areas chosen by missionaries for settlement because the Portuguese prohibited them from living in coastal areas. This is another region that benefits from volcanic soil, with more smallholder coffee farms than estates. Elevation: 1,350 to 1,950 meters. Harvest period: October to December (main season) and June to August (secondary season).

Kirinyaga Region

Situated on the slopes of Mount Kenya, adjacent to the Nyeri region, Kirinyaga is world-renowned for coffee with intense, complex flavors and solid mouthfeel. Together with Nyeri, it is recognized as one of Kenya's two finest regions. Most producers in this area are small-scale coffee farmers who join cooperatives, which play a coordinating role by providing washing stations where farmers bring their coffee cherries for processing.

"Kirinyaga" originally referred to Mount Kenya, but during British colonial rule, the name was considered difficult to remember, so the mountain's name was changed to "Mt. Kenya" instead of "Kirinyaga." Mount Kenya is Africa's second-highest peak, and although located in the tropics, its summit is often covered with snow. Kirinyaga means "white peaks." Mount Kenya is not only a UN protected area but also a popular tourist destination where wildlife congregates and feeds on the surrounding foothills and grasslands.

"Kirinyaga" comes from the Kikuyu people, meaning "white mountains," and is considered the dwelling place of gods. The Kikuyu are Kenya's largest ethnic group, accounting for one-fifth of the total population. Elevation: 1,300 to 1,900 meters. Harvest period: October to December (main season) and June to August (secondary season).

Thika Region

Located in a small town near Kenya's capital, Nairobi. There are many coffee fields around Nairobi, and while Thika is an industrial town, it is surrounded by agriculture and waterfalls. The Thika region has approximately 2,000 farmers. The cultivation history of Kenyan Thika coffee dates back to the late 19th century, when coffee varieties were introduced from the northern neighboring country Ethiopia. After variety improvement, the common varieties now include Bourbon, Kents (SL34, SL28), Typica, and Riuri 11. Currently, about 90% of coffee varieties are SL34 and SL28. The new variety Batian, released in 2007, has not yet been widely cultivated. Coffee from this region features bright fruit acidity, rich berry juice flavors, and honey-like sweetness. Elevation: 1,550-1,750 meters.

Kenyan Coffee Varieties

SL28 Coffee Variety

SL28 is one of Africa's most famous and respected varieties. Therefore, it has spread from its selection in Kenya in the 1930s to other parts of Africa (particularly Uganda's Arabica growing areas) and now to Latin America. The SL28 variety is suitable for medium to high altitude areas, has drought resistance, but is sensitive to major coffee diseases. SL28 is found in many parts of Kenya and remains highly productive even at 60-80 years of age.

SL28 was selected in 1935 as a single variety from drought-resistant populations in Tanganyika. In 1931, A.D. Trench, Senior Coffee Officer at Scott Laboratories, led visitors to Tanganyika (now Tanzania). According to historical records, he noticed a variety growing in the Modi region that seemed to have tolerance to drought, disease, and pests. Seeds were collected and brought to Scott Laboratories, where their drought resistance was confirmed.

SL34 Coffee Variety

SL34 was first selected in the late 1930s at Scott Agricultural Laboratories in Kenya. SL34 was selected from a tree at the Kabete Loresho estate in Kenya, which was known as the "French Mission."

In 1893, French missionaries established a mission in Taita Hills, Kenya, where they planted Bourbon coffee seeds from Réunion Island. In 1899, seedlings from Taita Hills were taken to another French mission in St. Austin (near Nairobi), and from there, seeds were distributed to settlers willing to grow coffee, which became the origin of so-called "French Mission" coffee. Because French missionaries historically transported coffee seeds directly from Réunion Island, French Mission is widely understood to be a Bourbon variety. However, recent genetic testing shows that SL34 is related to the Typica genome. This has created different controversies about the story that SL34 was selected from French Mission stock.

After separately cupping coffees from both varieties, FrontStreet Coffee believes that SL28 and SL34 have similar flavor profiles, both featuring complex, varied berry-like acidity and caramel-sweet aftertaste. Compared to SL28, SL34 has a heavier mouthfeel, with acidity tending toward berries like blackberry, with overall sweet-sour balance and caramel aftertaste. When SL28 cools down, it tends more toward blueberry-like acidity, with slightly elevated acidity and higher sweetness, matching Bourbon's characteristic high sweetness.

Kenyan Coffee Processing Method - Kenyan 72-Hour Washing

Kenya employs a repeated washing method after fermentation. Processing begins on the same day as harvest, selecting the highest quality coffee cherries for pulping and fermentation. Fermentation time is 24 hours, after which the beans are washed with clean river water. Then, they undergo another 24-hour fermentation in clean river water, followed by washing again. This cycle is repeated 3 times, reaching 72 hours total, thus called the Kenyan 72-hour fermentation washing method, abbreviated as [K72]. FrontStreet Coffee believes that coffee beans processed with the Kenyan 72-hour fermentation washing method, fermented at low temperatures for extended periods and finally dried and dehydrated, result in beans with brighter, cleaner, yet fuller flavors.

Kenyan Coffee Bean Grading

AA Plus (AA+): AA grade with particularly excellent cup quality (flavor, mouthfeel).

AA: Bean size: Screen Size 17-18.

AB: Bean size: Screen Size 15-16, accounting for the majority of production.

C: Bean size: smaller than AB.

TT: Lighter-weight beans sifted from AA and AB grades using air classifiers.

T: Lighter-weight beans sifted from C grade using air classifiers.

E Elephant Bean: Large mutant beans where two beans merge into one, also called elephant ear beans.

PB Peaberry: Round beans classified by shape, unrelated to flavor or weight.

Kenyan Coffee Profile

Region: Thika, Kenya

Processing Station: Asali Honey Processing Station

Elevation: 1,550-1,750 meters

Grade: AA TOP

Varieties: SL28, SL34

Processing Method: Kenyan 72-hour washing

FrontStreet Coffee Roasting Recommendations

Preheat roaster to 200°C, set damper to 3. After 30 seconds, turn on flame, adjust heat to 160, keep damper unchanged. Return to temperature point at 1'34", maintain heat, color changes to yellow at 5'30", grassy smell disappears, enter dehydration phase. Reduce heat to 130, lower heat to enter Maillard reaction. When reaching 178°C, reduce heat again to extend Maillard reaction time, open damper to 3.5.

At 7'45", dehydration is complete, reduce heat to 80. At 8'30", wrinkles and black spots appear on bean surface, toast smell turns to coffee aroma, preluding first crack. At this time, pay attention to listen for first crack sounds. At 8'52", first crack begins, open damper to 5, reduce heat to 50 to reduce caramelization degree. When first crack begins, heat absorption is strong, so it's recommended to maintain heat at this stage to prevent stalling. First crack development takes more time, which helps reduce acidity and develop flavors. Post-first crack development time is 2 minutes 10 seconds, drop at 191.6°C.

FrontStreet Coffee Cupping Report

Wet aroma has mature tomato and floral notes. Entry reveals cherry tomato and plum flavors, with bright acidity, clean mouthfeel, medium body, prominent sweetness in the mid-section with juice-like quality. Aftertaste features berry fragrance and brown sugar sweetness, with green tea aroma.

FrontStreet Coffee Brewing Recommendations

FrontStreet Coffee, considering that this bean uses a light-to-medium roast approach, will adopt higher water temperature and a faster flow rate dripper, mainly because high temperature is needed to extract its bright acidity characteristics, but we don't want over-extraction due to high temperature, so we choose the faster flow V60 dripper.

Coffee-to-water ratio: 1:15 (15g coffee: 225ml water)

Water temperature: 90°C~91°C

Grind size: Fine sugar (78% retention on #20 standard sieve)

First pour 30g of water for 30-second bloom, then pour 95g more (electronic scale shows about 125g), completing in about 1 minute. When water level drops to 2/3 of the coffee bed, pour the remaining 100g (electronic scale shows about 225g), completing in about 1 minute 40 seconds. At 2'00", drip filtration is complete, remove dripper, extraction finished.

Brewing Flavor

Entry reveals plum and cherry tomato flavors, with strong, solid acidity in mouthfeel, prominent sweetness in the mid-section with juice-like quality. Aftertaste features berry fragrance and brown sugar sweetness, with green tea aroma.

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