Why Is Kenya Coffee So Acidic and How Is It Graded?

Kenya coffee gets its acidity from variety and processing rather than roast level. The SL28 and SL34 cultivars, grown in high-altitude regions, produce the wild berry and citrus sharpness the country is known for, and the K72 washed method, which soaks the beans after fermentation, reinforces that clarity and brightness in the cup.

Grading in Kenya is based mainly on bean size, with AA the largest screen size, followed by AB and other classes. AA beans generally roast more evenly, and are used for pour-over or as SOE, a single origin espresso, where the berry acidity stays prominent against a full body.

Kenyan coffee, with its wild berry acidity, has become a beloved favorite among many coffee connoisseurs. But where exactly does its acidity come from? How do variety, region, grading system, and processing method influence the flavors in the cup? This article, from the perspective of Front Street Coffee, systematically reviews the cultivation history, main producing regions, and AA grade classification standards of Kenyan coffee, deeply analyzes the contribution of SL28 and SL34 varieties and the K72 washed processing method to acidity and cleanliness, and includes the pour-over parameters and SOE preparation demonstration for Front Street Kenya Asalia coffee beans, taking you through a comprehensive understanding of the unique charm of this African star bean.

For those who order pour-over coffee at Front Street stores, if they aren't looking for a specific flavor, most tend to prefer African coffee beans. But Africa is such a large continent with so many countries—how does everyone choose their own bean? For coffee enthusiasts just starting out, their first choice is most likely Ethiopia's Yirgacheffe or Sidamo. However, many coffee connoisseurs are actually more partial to coffee beans from Kenya, because the characteristic taste of Kenyan coffee is a wild berry acidity. Next, Front Street Coffee will delve into Kenyan coffee beans with everyone.

History

As we all know, coffee originated in Ethiopia. Although it is adjacent to Ethiopia, the birthplace of coffee, the history of coffee cultivation in Kenya is not particularly long. There are two versions of Kenya's coffee cultivation history:

It is generally believed that coffee was brought to Kenya by Holy Spirit Church priests at the end of the 19th century. The more common account is that in 1893, French Holy Spirit priests brought it to Kenya from Réunion Island (Bourbon Island, the place where Bourbon coffee was discovered), while others believe it was brought in from Ethiopia.

There is another account: according to Kenneth Davids, founder of Coffee Review, in his 2001 article "Coffees from Africa and Arabia: Kenya Coffee," he mentions that coffee was introduced to Kenya by the British around 1900.

What we do know is that Kenya became a colony of the British Empire in 1895, was controlled by the British Empire, and was classified as part of the "East Africa Protectorate." Therefore, the British controlled agriculture in the region during that period, including coffee cultivation. In 1933, the Kenya Coffee Board was established. In 1934, the auction system was established and is still in use today. It was not until the 1960s that Kenyans began to have the right to cultivate and process their own coffee.

By the late 1980s, Kenyan coffee reached its peak development period, with annual production reaching 130,000 tons. But in recent years, Kenya's coffee industry has shown signs of decline, with annual production of only around 40,000 tons. Fortunately, Kenyan authorities have formulated a coffee revitalization plan to save the country's declining coffee industry.

Producing Regions

Front Street Coffee, upon reviewing James Hoffmann's book "The World Atlas of Coffee," learned that most of Kenya's coffee comes from the country's central producing regions, and high-quality coffee also comes from there.

Among Kenya's 14 coffee producing regions, coffee from Kiambu and Muranga has bright acidity and a thick mouthfeel; coffee from Nyeri has bright blackberry and heavy oily body, along with citrus and even floral notes; coffee from Kirinyaga has bright fruit acidity, medium oily body, and delicate sweetness; coffee from Embu has suitable acidity, with balanced and clear flavors and a surprising aftertaste; coffee from Machakos has refreshing fruit acidity, delicate flavors, moderate mouthfeel, and a delicate and fresh aftertaste; coffee from Kisii and Elgon has solid sweetness and mild flavors.

Grading System

When ordering Kenyan coffee at cafes, as long as you look closely at the grade, it's not hard to notice the letters AA. Front Street Coffee's baristas are also asked by some coffee enthusiasts just starting out: Is Kenya AA the highest grade? How are the grades distinguished?

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

Front Street Coffee needs to emphasize here that coffee bean grades are determined before roasting, so don't think about sieving roasted coffee beans.

E: Kenya E is called Elephant Bean, large in size, and relatively low in production.

PB: PB stands for Peaberry, which is what everyone knows as round beans, oval in shape. Normal coffee cherries contain two coffee seeds, while peaberries contain only one seed.

AA: Kenya AA can be said to be the most common grade, larger in size, with a screen size of 17/18.

AB: Screen size of 16/17.

C: Screen size below 14.

TT: Large screen size but low density, yet quality sufficient to be classified as specialty coffee.

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

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

Why Is Kenyan Coffee So Acidic?

When a coffee enthusiast asks "I want the most acidic bean," Front Street Coffee's baristas will first recommend the Kenya Asalia on the menu. Kenya's bright and clean acidity is also considered a characteristic taste of Kenyan coffee .

Front Street Coffee: Kenya · Asalia Coffee Beans

Region: Thika, Kenya

Altitude: 1550m—1750m

Processing Method: K72 Washed Processing

Variety: SL28, SL34

If we want to discuss in depth how the acidity of Kenyan coffee beans comes about, we must mention Kenya's local growing environment, coffee varieties, and processing methods.

The red volcanic soil where Kenya grows coffee contains large amounts of phosphoric acid. In addition, Kenya's common SL28 and SL34 coffee varieties are Bourbon variants. Through cupping multiple Kenyan coffee beans, Front Street has also found that the berry acidity in these two varieties, SL28 and SL34, is prominent.

The reason Kenya's coffee flavor is so clean and bright is thanks to Kenya's unique post-processing method—the Kenya 72-hour washed processing method. The Kenya 72-hour washed processing method is also known as the K72 washed processing method.

After the coffee cherries are depulped, the parchment beans with mucilage still attached are placed into fermentation tanks without water for dry fermentation. Every 6—8 hours, water is introduced to wash the parchment beans and drained, repeating the dry fermentation. This stage takes 24 hours.

In the second stage, the fermentation tank is not filled with water; fermentation lasts 12—24 hours, then the beans are manually directed into washing channels, where most of the mucilage is removed by agitation.

The second stage repeats the fermentation step once more. In this stage, the fermentation tank is filled more fully with water, then secondary fermentation takes place in clean water. The secondary soaking lasts 12—24 hours, during which the small amount of residual sugar and mucilage on the surface of the parchment beans continues to ferment and is finally removed. Finally, the coffee beans are moved to drying beds for sun drying.

Front Street believes that coffee beans that have undergone Kenya 72-hour washed processing can have a cleaner, brighter yet fuller flavor.

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

Dripper: Hario V60

Water Temperature: 90℃—93℃

Dose: 15 grams

Coffee-to-Water Ratio: 1:15

Grind Size: EK43s #10 (80% passing rate on China Standard No. 20 sieve)

Front Street uses a three-stage pouring method: use 30 grams of water for a 30-second bloom, then pour in a circular motion to 125 grams in the second stage, wait for the water level to drop until the coffee bed is about to be exposed, continue pouring to 225 grams and stop, then remove the dripper once the coffee liquid has fully flowed into the server. Extraction time is 2 minutes.

When it comes to enjoying single-origin coffee, besides pour-over, SOE—which has become increasingly popular in cafes in recent years—has also become one of the extraction methods many people make at home. For the above fruity Kenyan coffee beans, some customers have asked Front Street whether they can be made into SOE americano or SOE latte. The answer is undoubtedly yes, of course there's no problem.

In Front Street's view, a good SOE first depends on good beans, then a roast level suitable for espresso machines, and only then ideal extraction and serving. The so-called "suitable roast" here is reflected in SOE in three requirements: first, to preserve the "terroir" of the producing region; second, to give the resulting espresso a good balance; and a crucial point—to provide the maker with higher extraction stability. Otherwise, either the coffee tastes bad or has no SOE characteristics at all, or the extraction difficulty is too high, and by the time the whole bag of beans is used up, you still haven't dialed in a satisfactory cup of SOE coffee.

Below, Front Street uses the equipment available in the store as a reference and the Kenya · Asalia coffee beans introduced earlier to demonstrate how to make an SOE.

Front Street's store coffee machine is the commercial single-group "Lelit Bianca," which can adjust extraction by changing pressure, with a maximum pressure of 11 bar. Home coffee machines only need to reach 9 bar of pressure to satisfy extraction and milk frothing functions, paired with an espresso grinder.

Front Street uses a double basket capacity, with a dose of about 18–20 grams; Front Street uses 20 grams of coffee powder when serving. Usually the ratio of coffee powder to coffee liquid is 1:1.5–1:2.5. 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 20–35 seconds, because under 20 seconds the coffee usually tastes thin, while over 35 seconds it is easy to over-extract and produce astringent and burnt bitterness. Front Street's espresso mostly falls within the range of 28–30 seconds.

Front Street first wipes the basket dry, turns on the grinder, grinds a double dose of coffee powder, places it on an electronic scale to adjust up or down until reaching 20 grams. Then use a tool to distribute the grounds evenly, tamp the coffee puck firmly to ensure more stable extraction. Then turn on the extraction switch to release water, moistening the group head while washing away stuck coffee grounds, gently lock the portafilter onto the group head, and begin pulling the extraction. When the electronic scale shows 40 grams of extracted coffee liquid at about 30 seconds, you can turn off the extraction switch. Pour the coffee liquid into an Espresso cup and enjoy.

The extracted Kenya · Asalia SOE can be drunk directly, but the taste will be very intense, so remember to pair it with a glass of water to rinse your mouth. When tasting, you can sense the light yellow crema and the berry, tomato, and cookie aromas of the coffee liquid below. If you cannot accept the strong bitterness of espresso, Front Street suggests that according to your preference, add ice water or warm water at a 1:4 ratio to make a refreshing and mellow Kenyan SOE americano, or add steamed fresh milk at a 1:6 ratio to soften the mouthfeel, making a delicious cup of Kenyan SOE latte.

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