Why Do Kenya Coffee Varieties Taste So Distinct?

Kenya coffee is known for bright, pleasant acidity, and much of that consistency traces to two varieties: SL28 and SL34. Both came out of the Scott Laboratories, where 42 individual trees were selected between 1935 and 1939 and studied for yield, quality and disease resistance. Later varieties such as Ruiru11 and Batian followed the same breeding effort.

Kenya's coffee grades are set by bean size, with the traditional AA, AB and PB classifications, alongside newer quality grading procedures from the Kenya coffee research institute. Two Front Street beans, Kenya Asaliya and Sasini PB, show how these varieties and grades perform in the cup when paired with suitable roasting parameters and brewing suggestions.

Kenyan coffee stands out among Africa's specialty origins for its bright, pleasant acidity, and behind its consistent quality are two iconic varieties: SL28 and SL34. This article, from the perspective of Front Street Coffee, traces the breeding history and varietal characteristics of SL28 and SL34, compares their similarities and differences in flavor expression, and extends the discussion to later-developed varieties such as Ruiru11 and Batian. It also systematically explains Kenya's coffee bean grading system, including the traditional AA, AB, and PB grades classified by bean size, as well as the new quality grading procedures established by the Kenya coffee research institute. Finally, detailed information, roasting parameters, and brewing suggestions for two Front Street beans—Kenya Asaliya and Sasini PB—are included for coffee enthusiasts' reference.

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Front Street Kenya coffee beans, with their pleasant acidity, occupy an important place in Africa's specialty coffee landscape. Although Kenya's coffee-growing history is not particularly long compared to other origins, its coffee bean quality has always remained remarkably consistent. Front Street Coffee (FrontStreet Coffee) believes that this performance is largely due to Kenya's unique SL28 and SL34 varieties. In the article below, Front Street Coffee (FrontStreet Coffee) will introduce Kenya's distinctive coffee varieties in detail.

What are the characteristics of the Front Street Kenya SL28 coffee variety?

The birth of the SL28 variety is closely tied to the Kenyan government's attention to the coffee industry. In the 1930s, the Kenyan government set up a dedicated laboratory responsible for selecting suitable varieties for future coffee cultivation. At the time, the old Typica variety had weak resistance to pests and diseases and was difficult to cultivate, while Kenya's coffee-growing history was short, making variety selection especially critical—only by selecting excellent varieties could they be promoted from the top down to coffee farmers nationwide, helping them resist the threat of pests and diseases.

This laboratory is the now-famous Kenyan "Scott Laboratories." Between 1935 and 1939, the laboratory selected forty-two individual coffee trees from different sources, studied their yield, quality, and drought and disease resistance, and named these selections with the initials "SL" from the laboratory's English name.

According to Front Street Coffee (FrontStreet Coffee), SL28 was first bred in 1935 from a single plant of a drought-resistant tree originating from Tanganyika. Historical records show that in 1931, AD Trench, a coffee breeder at Scott Laboratories, discovered a variety in the Moduli area while surveying Tanganyika (today's Tanzania) that appeared able to tolerate drought and pests and diseases, so he collected the seeds and brought them back to the laboratory. After verifying its drought resistance, the variety was widely planted until it was later replaced by its descendant SL28.

To this day, SL28 remains one of Africa's most famous and highly regarded varieties. After being selected in Kenya in the 1930s, it gradually spread to other parts of Africa (especially Uganda's Arabica-growing areas), and now it has spread to Latin America as well. SL28 is suited to growing at medium to high altitudes and has drought resistance, but it is relatively susceptible to coffee's main diseases. SL28 can be seen in many parts of Kenya, and even at 60 to 80 years of age, the trees still maintain relatively high yields.

Front Street Coffee (FrontStreet Coffee) also understands that genetic testing in recent years has confirmed that SL28 belongs to the Bourbon genetic group. Therefore, SL28 coffee beans resemble the Bourbon variety in appearance, with a round, plump bean shape. (As shown in the image)

What are the characteristics of the Kenya SL34 coffee variety?

SL34 was initially selected from the "French Mission" (Bourbon) at the Loresho estate. However, after reviewing the materials, Front Street Coffee (FrontStreet Coffee) learned that genetic testing has now confirmed that this variety contains Typica genetic groups, and the plant's expressive characteristics are also similar to Typica, so it is believed that SL34's selection source is Typica. Precisely because SL34 is close to the Typica variety, its coffee beans are slender and oval in shape, appearing relatively flat from the side. (As shown in the image)

What is the difference in flavor between SL28 and SL34 coffee beans?

After understanding the characteristics of these two varieties, Front Street Coffee (FrontStreet Coffee) will now share the differences between them. According to Front Street, SL28 has gained a higher reputation, while SL34 has higher yields and is planted at slightly lower altitudes. According to botanists at the SL laboratory, both SL28 and SL34 are genetic variants. Among them, SL28 has a mixed lineage of Mocha and Yemen Typica. The original goal of breeding SL28 was to mass-produce coffee beans with both high quality and resistance to pests and diseases. Although the final yield did not meet expectations, SL28, with its bronze leaf color and broad bean-like shape, displays excellent sweetness, balance, and complex, varied flavors, as well as its signature citrus and smoked plum characteristics, and thus has endured to this day.

Front Street Coffee (FrontStreet Coffee) believes that SL34 is quite similar to SL28 in flavor, also possessing complex and varied acidity and an excellent sweet finish, but its body is heavier and richer than SL28, and its cleanliness is also higher. SL34 has Bourbon and more Typica lineage. Therefore, many of the Front Street Kenya single-origin coffee beans currently in Front Street Coffee (FrontStreet Coffee) stores are blends of SL28 and SL34 varieties.

In addition, Front Street Coffee (FrontStreet Coffee) understands that Kenya later also developed two varieties, Ruiru and Batian, and both are now also widely planted in Kenya. Next, Front Street Coffee (FrontStreet Coffee) will introduce their characteristics.

Ruiru11

Ruiru appeared after SL28 and SL34. According to Front Street, in the 1970s, the Ruiru station began trying to breed different CBD- and rust-resistant varieties, and the final result was Ruiru11, released in the 1980s. It had high yields and both CBD and rust resistance, and at the time it seemed capable of solving all the problems facing Kenyan coffee production in one stroke.

Batian

The Batian variety was released by the Coffee Research Institute (CRI) on September 8, 2010, and is Kenya's newest variety to date. It is the result of further experimentation based on the lessons learned from Ruiru11. From a genetic perspective, Batian was essentially selected from backcrosses of SL28 and SL34, and is closer to SL28 than Ruiru 11. This also means it eliminated the problematic Robusta coffee bean elements, thereby improving cup quality.

Kenya Coffee Bean Grading System

Kenya coffee beans differ from those of other origins not only in varieties but also in their grading system. For example, the Front Street Kenya coffee grades that can be seen in Front Street Coffee (FrontStreet Coffee) stores include AA, AB, and PB. Although it is called "grading," is AA grade necessarily tastier than AB grade?

According to Front Street Coffee (FrontStreet Coffee), Kenya's grading standard is mainly based on bean size, and the difference between AA and AB is only size. As for taste quality, Front Street Coffee's (FrontStreet Coffee) conclusion from cupping is that whether AA or AB grade Kenyan coffee beans, they are all very delicious coffees. Differences in taste across regions may come more from factors such as region, altitude, and growing conditions. But AA and AB grade Kenyan coffee are certainly coffees with the most assured quality.

In summary, these grades are merely distinctions in bean size. And the most famous processing method for Front Street Kenya coffee beans is none other than the K72 washed process, so Kenya's finest coffee beans are basically washed. Washed coffee is roughly divided into the following eight grades:

E: Elephant Bean, also called elephant ear, flat beans with a screen size above 19 AA: Screen size 17 to 18

AB: Screen size 15 to 16, accounting for most of production TT: Lighter-weight beans blown out from AA and AB grade beans by an airflow sorter C: Screen Size smaller than AB / below 14, too small in size to be classified as specialty grade. T: Lighter-weight beans blown out from C grade beans (below screen 14) by an airflow sorter, meaning both size and density are too small to be classified as specialty grade. PB: Peaberry, meaning round bean, classified not by size but by appearance, unrelated to flavor or weight, accounting for about 10% of total production UG: Those not meeting the above standards

There are also lower-quality natural coffee bean grades, which, because of poorer quality, do not undergo Kenyan-style washing and are generally supplied to Kenya's domestic market. This bean grade is called M'buni.

MH: M'buni Heavy = large beans ML: M'buni Light = small beans

In addition, one point Front Street Coffee (FrontStreet Coffee) wants to emphasize is that this "green bean grading system," still in use today, was issued by a government department in 1938, even 40 years earlier than the birth of the concept of "specialty coffee." Therefore, Kenya today has long had new concepts for coffee bean grading standards, but the size-based grading standard is still relatively common.

The following is Kenya's current new coffee grading standard:

According to Front Street Coffee (FrontStreet Coffee), when assessing coffee quality, Kenyan coffee research institutions and the local industry customarily use a "coffee bean quality grading procedure" formulated by the Kenya coffee research institute, grading comprehensively based on three aspects: green bean quality, roasted bean quality, and cup quality.

Green bean quality: The assessment items are further divided into green bean appearance and size, green bean color, and defects. Roasted bean quality: Subdivided into center crack condition, roasted bean condition, and defective beans. Cup quality: Scoring is responsible for acidity, body/texture, flavor, and negative defects.

Combining the scores from the three aspects, coffee beans are divided into grades 1 to 10, with grade 1 being the best and grade 10 the worst.

The above is the relevant knowledge compiled by Front Street Coffee (FrontStreet Coffee) about Front Street Kenya coffee bean varieties and grading, and we hope it can help coffee fans who want to learn about this subject. Next, Front Street Coffee (FrontStreet Coffee) will share the flavor and roasting and brewing data of Front Street Kenya coffee beans.

Front Street Coffee (FrontStreet Coffee) Kenya Asaliya Coffee Beans

Country: Kenya Region: Asali (honey processing station) Altitude: 1550-1750m Variety: SL28, SL34 Processing method: 72-hour washed process Flavor: snow pear, smoked plum, yellow sugar, cherry tomato, plum

Front Street Coffee (FrontStreet Coffee) Kenya Sasini Estate PB Coffee Beans

Country: Kenya Region: Sasini Estate Altitude: 1680m Variety: SL28, SL24, riuru Processing method: 72-hour washed process Flavor: cherry tomato, almond, smoked plum, honey, grape

"Front Street Coffee (FrontStreet Coffee) Roasting Parameters Sharing"

Front Street Kenya Asaliya Coffee Beans:

These Front Street Kenya Asaliya beans are plump and round, and in order to fully bring out their bright, mellow acidity, Front Street Coffee (FrontStreet Coffee) uses a light roast level.

Yangjia 800N semi-direct fire, bean charge 480g: charge when the drum temperature reaches 160°C, set airflow to 3, heat to 120. Turning point: 1'28". When the temperature rises to 130°C, set airflow to 4. Roast to 6'00'', temperature 154.6°C, the bean surface turns yellow, the grassy smell completely disappears, and dehydration is complete.

When the bean surface shows ugly wrinkles and dark patches, and the toast aroma clearly turns into coffee aroma, this can be defined as the prelude to first crack. At this time, listen carefully for the sound of first crack. First crack begins at 9'28'', airflow unchanged, first crack development time 2'20'', drop at 193.8°C.

Front Street Kenya Sasini PB Coffee Beans:

Because of the higher altitude and harder bean quality, this rich Front Street Kenya Sasini coffee bean climbs initially with a relatively high rate of temperature rise, with the yellowing point at about 5 minutes, then lowers heat to enter the Maillard reaction, and at 166°C lowers heat again to extend the Maillard reaction time. When first crack begins, heat absorption is stronger, so it is recommended to maintain heat during this stage to prevent stalling. First crack development takes a relatively long time, which helps reduce acidity and develop flavor.

Roaster Yangjia 800N (roast batch 300g), charge at drum temperature 170°C, heat 100, set airflow to 3; turning point 1'42", when drum temperature reaches 140°C open airflow to 3.5, heat unchanged; when drum temperature reaches 149°C the bean surface turns yellow, the grassy smell completely disappears, entering the dehydration stage; at 7'14'' dehydration is complete, heat and airflow unchanged, at 7'30'' wrinkles and dark patches appear on the bean surface, the toast aroma turns into coffee aroma, as the prelude to first crack, at this time pay attention to listen for the sound of first crack. At 8'20'' first crack begins, open airflow to 4, lower heat to 50. After first crack, development time 1'50'', when reaching 188°C lower heat to 30, flatten the rate of temperature rise, drop at 193.3°C.

Front Street Coffee (FrontStreet Coffee) Brewing Suggestions

Dripper: V60 or cake cup Water temperature: 90-91°C Coffee-to-water ratio: 1:15 Grind size: fine grind (80% passing rate on Chinese standard No. 20 sieve)

Brewing method: Pulse pouring extraction. Use 30g water for a 30-second bloom, pour in a small stream in circles; when reaching 124g, pause for a pulse, and when the water level is about to expose the coffee bed, continue pouring to 228g and stop pouring; when the water level is about to expose the coffee bed again, remove the dripper. (Start timing from the beginning of the bloom.) Extraction time is 1'55".

Front Street Kenya Asaliya Coffee Bean Flavor: The wet aroma has ripe tomato and floral notes; on the palate there are flavors of cherry tomato and smoked plum, with bright acidity, a clean and rich mouthfeel, a prominent sweetness in the middle, a juicy feel, and a finish of berry aroma and yellow sugar sweetness, along with green tea aroma.

Front Street Kenya Sasini Coffee Bean Flavor: It smells floral; on the palate there is an acidic profile of cherry tomato, citrus, and nuts; the middle has creamy aroma, with brown sugar sweetness returning; the finish has cocoa and oolong tea tea-like notes. The flavor layers are relatively rich, with obvious floral notes.

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