How Does the Coffee Beans Process Shape Kenyan AA Flavor?

Kenyan AA grade refers to the largest screen size of the bean, and the cup behind it comes from high-altitude growing regions, SL28 and SL34 varieties, and the K72 washed fermentation process. That combination produces the bright fruit acidity, dark plum and cherry tomato notes, and thick, juicy body the country is known for.

The coffee beans process matters as much as the variety. K72 calls for a long washed fermentation that helps build the dense berry-like acidity, while a medium-light roast and V60 pour-over bring out yellow sugar sweetness. Growing areas such as Thika, Kirinyaga, and Nyeri each add their own regional character to the cup.

Kenyan coffee stands out in the global specialty coffee scene with its bright fruit acidity and full-bodied berry flavors, and the AA grade is among its most closely watched representatives. This article will start with Kenya's geography and growing conditions, systematically sorting out the altitude, varieties, and flavor differences of six major producing regions including Thika, Kirinyaga, and Nyeri, and explain in detail the evolution of Kenya's coffee auction system and direct trade. At the same time, the article will take a deep look at the origins of classic varieties such as SL28 and SL34, as well as the famous K72-hour washed fermentation process, helping readers understand the reasons behind Kenyan coffee's high acidity and thick juicy mouthfeel. Finally, using Front Street Coffee's Kenya Asaliya as an example, it shares a medium-light roast approach and V60 pour-over parameters, presenting the specific flavor expression of dark plum, cherry tomato, and yellow sugar sweetness.

That bright fruit acidity of Kenyan coffee, along with its gorgeous, solid, and outstanding mouthfeel, is almost unforgettable to anyone who has tasted it. Front Street has encountered many beans from various Kenyan producing regions during cupping, and if high acidity is the soul of a good cup of coffee, then Kenyan coffee undoubtedly best represents that soul. Kenyan beans also have another unique trait: usually coffee with bright acidity does not also have a thick mouthfeel. For example, Ethiopian beans have a clean, refreshing direction on the palate, while Kenyan coffee can bring a berry juice sensation that coats the entire mouth, with a texture similar to tomato juice.

Kenyan Coffee Cultivation

Kenya is located in eastern Africa, with the equator passing through its center and the East African Rift Valley running north to south. It borders Somalia to the east, Tanzania to the south, Uganda to the west, Ethiopia and Sudan to the north, and faces the Indian Ocean to the southeast. Highlands are widespread across the country, with an average altitude of about 1,500 meters. Mount Kirinyaga (Mount Kenya) in the center has an altitude of 5,199 meters, with snow on its summit year-round, and is the second-highest peak in Africa.

Kenya is a tropical producing region with two rainy seasons each year, so it can also harvest two seasons, with 60% concentrated from October to December and the other 40% from June to August. Coffee is mainly planted in volcanic soil at altitudes of 1,600-2,100 meters from the capital Nairobi to the areas around the Kenyan highlands. This altitude is conducive to the development of coffee bean flavor because the lower temperatures in the highlands slow growth, allowing the aromatic components of the coffee beans to fully accumulate, giving more prominent fruit acidity and a harder texture. This fertile, crescent-shaped coffee zone is the main producing area for Kenya's specialty beans.

Kenyan Producing Regions

Kenyan coffee is mainly based on six major producing regions: Thika, Kirinyaga, Mt. Kenya West, Nyeri, Kiambu, and Muranga. The harvest periods of the six major producing regions are all concentrated from October to December each year (main crop season) and from June to August (secondary crop season).

Thika

Thika is a small town near Kenya's capital, Nairobi. A large number of coffee fields are distributed around Nairobi. Thika itself is an industrial town, but it is surrounded by agricultural areas and waterfalls. There are about 2,000 farmers in the Thika area. The history of coffee cultivation in Thika, Kenya, can be traced back to the late 19th century, when coffee tree species were introduced from the northern neighboring country Ethiopia. After local variety improvement, the common varieties currently include four: Bourbon, Kents (SL34, SL28), Typica, and Riuri 11. About 90% of the planted varieties are now SL34 and SL28. The new variety Batian, released in 2007, has not yet been planted on a large scale. The flavor performance of this producing region is bright fruit acidity, a thick berry juice sensation, and honey-like sweetness.

Altitude: 1,550-1,750 meters

Varieties: sl-28, sl-34

Kirinyaga

The Kirinyaga producing region is located on the slopes of Mount Kenya, adjacent to the Nyeri producing region, and is world-famous for coffee with strong flavor, rich layers, and a solid mouthfeel. Together with the Nyeri producing region, it is recognized as one of the two currently best-producing regions in Kenya. Producers in this region are mostly small coffee farmers who join cooperatives. The cooperatives play an integrating role and provide wet mills. Coffee farmers send coffee cherries to the cooperative's wet mill for processing. The flavor of this producing region has bright fruit acidity, a medium oily mouthfeel, and delicate sweetness.

Altitude: 1,300~1,900 meters

Varieties: SL-28, SL-34, Ruiru11, Batian.

Mt. Kenya West

Mt. Kenya West includes Kisii and the Bungoma area of Mount Elgon. Among them, Kisii is located in southwestern Kenya, not far from Lake Victoria, and is a relatively small producing region. Most coffee beans come from common cooperatives formed by small producers. The coffee flavor of this producing region is very different from that of the central producing regions, with roasted nuts and soft fruit acidity, and is widely loved by buyers who do not like bright acidity.

Altitude: 1,450~1,800 meters

Varieties: SL-28, SL-34, K7

Nyeri

Nyeri, located in central Kenya, is where the extinct volcano Mount Kenya is found. The red soil of this region nurtures Kenya's best coffee. Agriculture is extremely important here, and coffee is the main crop among them. Common cooperatives formed by smallholder farmers are more common than large estates. This region has two harvests, but coffee from the main crop season is usually of higher quality. This producing region has a bright berry juice sensation, plus citrus and slight floral notes. The coffee beans grown here have made Kenyan coffee famous worldwide.

Altitude: 1,200~2,300 meters

Varieties: SL-28, SL-34, Ruriu11, Batian

Kiambu

This producing region in central Kenya has the highest-altitude coffee-growing area in the region. However, some coffee trees at high altitudes develop dieback and then stop growing. This producing region is named after the town of Nakuru. Coffee cultivation here includes both estates and smallholder farmers, but the yield is relatively small.

Altitude: 1,850~2,200 meters

Varieties: SL-28, SL-34, Ruiru11, Batian

Muranga

The Muranga producing region belongs to Central Province, and there are about 100,000 coffee farmers in this area. This inland producing region was where the first missionaries chose to settle because the Portuguese prohibited them from living in the coastal areas. This is another producing region that benefits from volcanic soil, with more smallholder coffee farmers than estates. The coffee of this producing region has bright acidity and a thick juice mouthfeel.

Altitude: 1,350~1,950 meters

Varieties: SL-28, SL-34, Ruiru11, Batian

Kenyan Coffee Auctions and Direct Trade

Almost all Kenyan coffee must be sold through the coffee exchange located in the capital, Nairobi. Every Tuesday during the harvest season, the coffee exchange holds a coffee auction. Licensed traders receive green bean samples in advance, choose the green beans they prefer after cupping, and the highest bidder wins in the subsequent auction. Kenya's coffee auction system is considered the model for today's popular COE competitions and is regarded as the most transparent and efficient trade method, effectively encouraging growers to pursue quality and achieving the result of high prices for high quality.

Although the coffee auction system has effectively raised the selling prices of high-quality coffee, it is not without drawbacks: first, the existence of many trade intermediaries erodes the interests of coffee farmers, and the high prices obtained at auction cannot be fully passed back to the coffee farmers who work hard; second, auctioned coffee is difficult to trace accurately for production information, and for the increasingly prosperous specialty coffee market, traceability is an important criterion for evaluating green coffee. Based on the above factors, the Kenyan government has begun to relax restrictions on direct coffee trade. Nationally certified agents can directly sell coffee beans to customers such as specialty coffee roasters abroad. Direct trade can give farmers producing high-quality coffee more rewards.

FrontStreet Coffee: Kenya Asaliya Coffee Beans

Producing region: Thika producing region, Kenya

Altitude: 1,550-1,750 meters

Varieties: SL28, SL34

Processing method: washed processing

Coffee Bean Varieties

SL-28 and SL-34. These are two of the 40 varieties obtained from the research plan led by Guy Gibson of Scott Laboratories. The laboratory cultivated and named them in 1930 AD. According to SL laboratory botanists, SL28 and SL34 are genetic variants. They account for the vast majority of Kenya's high-quality coffee production, but these varieties are susceptible to leaf rust. SL34 has French missionary, Bourbon, and more Typica ancestry. The bronze leaf color and broad-bean-shaped beans have excellent sweetness, balance, and complex, varied flavors, as well as notable citrus and dark plum characteristics.

Ruiru 11: In 1985, when global leaf rust broke out on a large scale, Kenya developed this hybrid variety under that background with emphasis on yield rather than quality, but its flavor quality is far inferior to the earlier sl28 and sl34, and it has not developed in the specialty coffee world. However, many suppliers, even importers of famous coffees, mix this hybrid bean into blends to reduce costs.

Coffee Bean Processing Method: Kenyan 72-Hour Wash

Kenya adopts a repeated cyclic processing method of fermentation followed by washing. Post-processing is carried out on the day of harvest, selecting the highest-quality coffee cherries for depulping and fermentation. The fermentation time is 24 hours, and after 24 hours they are washed with clean river water. Then they are fermented again with clean river water for 24 hours and washed again. After repeating the cycle 3 times, it reaches 72 hours, so it is called the Kenyan-style 72-hour fermentation washed processing method, abbreviated as [K72].

① First wash and fermentation

After the coffee cherries are harvested, they first go through water-flow specific gravity sorting. The principle is to use the density and mass differences of the coffee fruit itself for screening; coffee beans with high density (heavy mass) sink into the water, while coffee beans with low density float. Fully ripe, high-quality coffee cherries have high density, and these are selected for further processing.

After selecting high-quality and sufficiently ripe fruit, the skin is removed, and they are washed and soaked so that the mucilage attached to the outer layer of the green beans undergoes fermentation. Pectin has natural sugars and alcohols, which play a crucial role in the development of coffee sweetness, acidity, and overall flavor. The fermentation time lasts as long as 24 hours. After fermentation, 80-90% of the pectin can be removed, leaving only the flavor inside the coffee beans.

② Second wash and fermentation

Next comes the second washing and fermentation procedure. After the coffee beans from the previous stage are cleaned, they are soaked in water again for 24-48 hours. This process increases protein and amino acids, and the acidity of the coffee beans thus develops complex, delicate layers in the mouthfeel. Finally, all remaining pectin is removed, and the coffee beans are moved to raised drying beds for sun drying.

The fermentation time lasts as long as 24 hours. After fermentation, 80-90% of the pectin can be removed, leaving only the flavor inside the coffee beans. Finally, all remaining pectin is removed, and the coffee beans are moved to raised drying beds for sun drying. The drying time depends on weather conditions and generally takes about 5-10 days to complete. Front Street believes that coffee beans processed by the Kenyan 72-hour fermentation washed method are fermented for a long time at low temperatures and finally completed after drying and dehydration, which can give the beans a brighter, cleaner yet fuller flavor.

Coffee Bean Grading System (Graded by Size)

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

AA screen size: 17-18 mesh.

AB screen size: 15-16 mesh, accounting for most of the production.

C screen size: smaller than AB.

TT: from AA and AB grade beans, lighter-weight beans blown out by an airflow sorter.

T: from C grade beans, lighter-weight beans blown out by an airflow sorter.

E Elephant Bean: a large mutant bean formed by two beans combined, also called elephant ear.

PB Peaberry: classified by appearance, unrelated to flavor or weight.

For green coffee beans of the two grades AA and AB, a special grading based on cupping results has been added (not officially recognized by the Kenyan state, but set by exporters), from high to low as TOP, PLUS (+), FAQ. The flavor grade of Kenya Asaliya on FrontStreet Coffee's bean list has reached the TOP grade. However, as mentioned earlier, this is not an officially recognized grading system. Several Kenyan producing-region coffee beans purchased by FrontStreet Coffee do not each carry a flavor grade, so there is no need to obsess too much over this. Generally, once they reach the AA and AB grades, the flavor is already by default considered very high quality.

The Kenya Asaliya launched by FrontStreet Coffee comes from AA-grade coffee beans from the Thika producing region. Next, Front Street will talk about how we roast this bean and brew this bean to see how the flavor performs.

FrontStreet Coffee Roasting Analysis

When FrontStreet Coffee roasts this Kenyan coffee bean, considering the need to highlight its rich fruit acidity and full berry juice mouthfeel, a medium-light roast is used.

Front Street Brewing Suggestions

FrontStreet Coffee, considering that this bean uses a medium-light roasting method, will use a higher water temperature and a faster-flow dripper, mainly because high temperature is needed to extract its bright acidic tone, but we do not want high temperature to cause over-extraction, so a faster-flow V60 dripper is chosen.

Coffee-to-water ratio: 1:15

Coffee grounds: 15g

Total water poured: 225ml

Water temperature: 91°C

Grind size: fine granulated sugar texture | EK43s setting 10 (80% pass rate on No. 20 standard sieve)

For the first stage, pour 30 grams of water for a 30-second bloom, then pour 95 grams (electronic scale shows about 125 grams), finishing the pour in about 1 minute. When the water level drops to 2/3 of the coffee bed, pour the remaining 100 grams (electronic scale shows about 225 grams), finishing the pour in about 1 minute 40 seconds. Drip completes at 2'00", remove the dripper, and extraction is complete.

Brewing flavor: on the palate there are flavors of dark plum and cherry tomato. In the mouthfeel, the acidity is strong and thick, the mid-palate has prominent sweetness with a juicy sensation, and the finish has berry aroma and yellow sugar sweetness, along with green tea aroma.

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