How is Kenyan AA coffee turned into an SOE espresso?

Kenyan AA coffee beans deliver the origin's signature wild berry acidity and a clean, bright mouthfeel. The character comes from red volcanic soil, the SL28 and SL34 varieties, and the K72 washing process. For an SOE espresso, those same qualities concentrate into a dense, fruit-forward shot with a crisp finish and notable sweetness.

Kenya grades its coffee by bean size, so AA marks the largest screen size and usually the most consistent lots. Cultivation began when missionaries and British colonists brought coffee in the late nineteenth century, and the Kenya Coffee Board was set up in 1933. Front Street's Kenya Asalia is a practical bean for both pour-over and SOE espresso.

Kenyan coffee is renowned for its wild berry-like acidity and clean, bright mouthfeel, making it a favorite among many coffee connoisseurs. From the perspective of Front Street Coffee, this article systematically reviews the history of Kenyan coffee cultivation, major producing regions, and grading standards, while delving into the causes behind its signature acidity—red volcanic soil, the SL28 and SL34 varieties, and the unique K72 washing process. At the same time, using Kenya Asalia coffee beans as an example, the article shares pour-over parameters and SOE espresso preparation steps to help coffee enthusiasts recreate a full-flavored cup of Kenyan coffee at home.

When customers at Front Street's shop order pour-over coffee without specifying a flavor preference, most tend to lean toward beans from African producing regions. However, Africa is vast with numerous producing countries, and everyone's approach to selecting beans differs. Beginners new to specialty coffee often start with Ethiopia's Yirgacheffe or Sidamo. But many seasoned coffee enthusiasts are particularly fond of Kenyan coffee, because Kenyan coffee's characteristic taste presents a bold and expressive berry-like acidity. Next, Front Street Coffee (FrontStreet Coffee) will take you on an in-depth look at Kenyan coffee beans.

History

It is widely known that coffee originated in Ethiopia. Although Kenya is adjacent to the birthplace, its coffee cultivation history is not particularly long. Regarding the origins of Kenyan coffee, there are two main accounts:

One account holds that at the end of the nineteenth century, Holy Spirit missionaries brought coffee to Kenya. The more common version is that in 1893, French Holy Spirit priests introduced it from Réunion Island (formerly Bourbon Island, where Bourbon coffee was discovered), while others believe it was introduced from Ethiopia.

The other account comes from an article titled "Coffees from Africa and Arabia: Kenya Coffee," published in 2001 by Kenneth Davids, founder of Coffee Review. The article mentions that coffee was introduced to Kenya by the British around 1900.

What can be confirmed is that Kenya became a British colony in 1895 and was incorporated into the "East Africa Protectorate," during which the British controlled local agriculture, and coffee cultivation was naturally part of it. In 1933, the Kenya Coffee Board was established. In 1934, the auction system was set up and remains in use today. It was not until the 1960s that Kenyans truly gained the right to independently cultivate and process coffee.

In the late 1980s, Kenyan coffee reached its peak of development, with annual production once reaching 130,000 tons. But in recent years, the country's coffee industry has shrunk, with annual production maintained at only around 40,000 tons. Fortunately, the Kenyan government has formulated a coffee revitalization plan in an attempt to reverse the industry's decline.

Producing Regions

After consulting James Hoffmann's "The World Atlas of Coffee," Front Street Coffee (FrontStreet Coffee) learned that Kenyan coffee is mainly distributed in the country's central producing region, and outstanding-quality coffee also comes from this area.

Among Kenya's 14 coffee-producing regions, Kiambu and Muranga produce coffee with bright acidity and a thick mouthfeel; the Nyeri region features distinct blackberry notes and a rich, oily body, along with citrus and even floral aromas; Kirinyaga is known for bright fruit acidity, a medium oily body, and delicate sweetness; the Embu region has moderate acidity, balanced and clear flavors, and a pleasant aftertaste; Machakos coffee has crisp fruit acidity, delicate flavors, a moderate mouthfeel, and a fresh aftertaste; and the Kisii and Elgon regions produce coffee with solid sweetness and mild flavors.

Grading System

When ordering Kenyan coffee at a café, as long as you pay attention to the grade information, it is not hard to notice the two letters AA. Front Street Coffee (FrontStreet Coffee) baristas are also often asked by beginners: Is Kenya AA the highest grade? How exactly are these grades divided?

Kenyan coffee beans are roughly divided into eight grades based on bean size: E, PB, AA, AB, C, TT, T, MH/ML.

Front Street Coffee (FrontStreet Coffee) particularly reminds everyone here that coffee bean grades are determined before roasting, so do not attempt to screen and grade roasted beans.

E: Kenyan elephant beans, large in size, with relatively scarce production.

PB: Peaberry, the common round bean, oval in shape. A normal coffee cherry contains two seeds, while a peaberry contains only one.

AA: Kenya AA is the most common grade, with larger beans sized at 17/18 screen.

AB: Bean size is 16/17 screen.

C: Bean size below 14 screen.

TT: Large screen size but relatively low density; quality can still be classified as specialty coffee.

T: Below 14 screen, small beans, with density and quality insufficient to be classified as specialty.

MH/ML: Low-quality natural-process beans, mostly overripe beans dried on the tree.

Why Is Kenyan Coffee So Acidic?

When coffee enthusiasts ask "which bean is the most acidic," Front Street Coffee (FrontStreet Coffee) baristas usually first recommend the Kenya Asalia on the menu. Kenya's acidity is bright and clean, which is precisely a typical expression of Kenyan coffee's characteristic taste.

Front Street Coffee (FrontStreet Coffee): Kenya·Asalia Coffee Beans

Region: Thika, Kenya

Altitude: 1550m—1750m

Processing Method: K72 Washed Process

Varieties: SL28, SL34

To explore in depth the source of Kenyan coffee's acidity, we must discuss three aspects: the local growing environment, coffee varieties, and processing methods.

The red volcanic soil where Kenya grows coffee is rich in phosphoric acid. In addition, the commonly found SL28 and SL34 are both Bourbon variants. After cupping many Kenyan coffee beans, Front Street found that these two varieties perform particularly prominently in berry-like acidity.

The reason Kenyan coffee's flavor is clean and bright also benefits from its unique post-processing method—the Kenyan 72-hour washing process, also known as the K72 washed process.

After the coffee cherries are depulped, the parchment beans with mucilage still attached are placed into fermentation tanks and undergo dry fermentation without adding water. Every 6 to 8 hours, water is introduced to wash and scrub the parchment beans and then drained, repeating the dry fermentation; this stage takes 24 hours.

In the second stage, the fermentation tank is not filled with water, and fermentation lasts 12 to 24 hours, after which the beans are manually channeled into washing channels, where most of the mucilage is removed by stirring.

After the second stage, the fermentation step must be repeated once more. In this stage, the fermentation tank is filled with more water, and then a second fermentation is carried out in clean water, with the second soaking lasting 12 to 24 hours. The small amount of residual sugar and mucilage on the surface of the parchment beans continues to ferment and is ultimately removed. Finally, the coffee beans are moved to drying beds for sun drying.

Front Street believes that coffee beans that have undergone the Kenyan 72-hour washing process can present a cleaner and brighter flavor without losing fullness.

Front Street's brewing parameters for the Kenya Asalia coffee beans are as follows:

Dripper: Hario V60

Water Temperature: 90℃—93℃

Dose: 15g

Coffee-to-Water Ratio: 1:15

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

Front Street uses a three-stage pouring method: bloom with 30g of water for 30 seconds, then pour in a circular motion in the second stage until 125g, and when the water level drops to just before the coffee bed is exposed, continue pouring until 225g and stop. Once the coffee liquid has fully flowed into the server, remove the dripper. Total extraction time is 2 minutes.

In terms of tasting single-origin coffee, besides pour-over, SOE—which has become increasingly popular in cafés in recent years—has also become an extraction choice many people make at home. Regarding the above-mentioned fruit-forward Kenyan coffee beans, some customers have asked Front Street whether it can be made into an SOE Americano or SOE Latte, and the answer is undoubtedly yes.

In Front Street's view, a good SOE first depends on good beans, then on a roast level suitable for espresso machines, and finally on ideal extraction and serving. The so-called "suitable roast" is reflected in three requirements for SOE: first, preserving the producing region's "taste of place"; second, giving the espresso a good sense of balance; and third, providing the maker with greater extraction stability. Otherwise, either the coffee tastes poor and lacks any SOE character, or extraction is too difficult, and even after finishing the entire bag, one still cannot dial in a satisfying cup of SOE.

Below, using the shop's supporting equipment as a reference, Front Street will demonstrate the SOE-making process using the Kenya·Asalia coffee beans introduced earlier.

The coffee machine used at Front Street's shop is the commercial single-group "Lelit Bianca," which can adjust extraction by changing pressure, with a maximum pressure of up to 11 bar. A home espresso machine only needs to reach 9 bar pressure to meet the needs of extraction and milk frothing, paired with an espresso grinder.

Front Street uses a double basket capacity, with a dose of about 18 to 20 grams, and uses 20 grams of coffee powder when serving. Usually the ratio of coffee grounds to espresso liquid is between 1:1.5 and 1:2.5, and Front Street's extraction ratio is 1:2, meaning 20 grams of coffee powder extracts 40 grams of coffee liquid. Time is related to the flow rate of the coffee powder; generally, a single extraction is controlled within 20 to 35 seconds, because within 20 seconds the coffee taste is usually thin, while exceeding 35 seconds easily leads to over-extraction, producing sour, astringent, and burnt bitter flavors. Front Street's espresso mostly falls within the 28 to 30 second range.

Front Street first wipes the portafilter basket dry, turns on the grinder, grinds a double dose of coffee powder, places it on the electronic scale, and adjusts to 20 grams. Then use a tool to distribute the grounds evenly and tamp the coffee puck firmly to ensure more stable extraction. Next, turn on the extraction switch to release water, wetting the group head while flushing away attached coffee grounds, gently lock the portafilter onto the group head, and begin the extraction. When the electronic scale shows 40 grams of extracted coffee liquid at about 30 seconds, the extraction switch can be turned off. Pour the coffee liquid into an Espresso cup and enjoy.

The extracted Kenya·Asalia SOE can be drunk directly, but the taste is very intense, so remember to pair it with a glass of water to rinse your mouth. When tasting, you can perceive light-yellow crema and aromas of berries, tomato, and cookies in the coffee liquid beneath. If you cannot accept the strong bitterness of espresso, Front Street suggests adding ice water or warm water at a 1:4 ratio according to personal preference to make a refreshing and mellow Kenyan SOE Americano; or add frothed fresh milk at a 1:6 ratio to soften the mouthfeel, making a delicious cup of Kenyan SOE Latte.

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