Kenya Coffee Beans SL28 SL34 Varieties K72 Washed Processing Method Characteristics and Stories

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As the specialty coffee market continues to grow, beyond the common natural and washed processing methods, various processing methods have emerged in the vision of coffee enthusiasts. For example, the Kenya K72 washed processing method, which is an improvement on the traditional washed processing method, is quite distinctive. In this article, FrontStreet Coffee will explain what exactly the K72 processing method entails in Kenya.

What is Kenya's K72 Washed Processing Method?

As FrontStreet Coffee mentioned above, this processing method is an improvement based on the traditional washed processing method. Kenya first adopted a cyclic repeated processing method of fermentation followed by washing. Processing begins on the day of harvest, selecting the highest quality coffee berries for depulping and fermentation. The fermentation time is 24 hours, after which the beans are washed with clean river water. Then, they are fermented again in clean river water for 24 hours, followed by another wash. This cycle is repeated 3 times, reaching 72 hours total, hence the name Kenyan 72-hour fermentation washed processing method, abbreviated as K72 processing method.

K72 Fermentation Washed Processing Method Flow:

① First Wash and Fermentation

After coffee berries are harvested, they first undergo water density sorting. The principle is to use the density and quality differences of the coffee fruit itself for screening; high-density (heavy-weight) coffee beans will sink in water, while low-density coffee beans will float. Fully ripe, high-quality coffee fruits have high density, and they are selected for further processing.

After selecting high-quality and sufficiently ripe fruits, the skin is removed for washed soaking, allowing the mucilage attached to the outer layer of the raw beans to ferment. The mucilage contains natural sugars and alcohols, which play a crucial role in the development of coffee's sweetness, acidity, and overall flavor. The fermentation time lasts up to 24 hours, after which 80-90% of the mucilage can be removed, leaving only the flavor within the coffee beans.

② Second Wash and Fermentation

Next, it enters the second wash and fermentation process. After the coffee beans from the previous stage are cleaned, they are soaked again in water for 24-48 hours. This process increases proteins and amino acids, giving the coffee beans complex and delicate layered acidity. Finally, all remaining mucilage is removed, and the coffee beans are moved to raised racks for sun drying.

The fermentation time lasts up to 24 hours, after which 80-90% of the mucilage can be removed, leaving only the flavor within the coffee beans. Finally, all remaining mucilage is removed, and the coffee beans are moved to raised racks for sun drying. The drying time varies depending on weather conditions, generally taking about 5-10 days to complete.

FrontStreet Coffee believes that coffee beans processed with Kenya's 72-hour fermentation washed method, which involves long-term fermentation at low temperatures and final sun drying for dehydration, result in beans with brighter, cleaner, yet fuller flavors.

Kenya Coffee Growing Conditions

Of course, the quality of a coffee bean cannot be determined solely by the processing method. More importantly, the inherent quality of the coffee bean itself must be strong enough. FrontStreet Coffee has often mentioned in previous articles that the flavor of a coffee bean depends on its growing region, variety, and processing method. This means that the quality of the processing method is built on the premise of high-quality coffee fruit.

Kenya is located in eastern Africa, with the equator crossing through the central part 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 mostly highland, with an average altitude of 1500 meters. Mount Kirinyaga (Mount Kenya) in central Kenya reaches 5199 meters above sea level, with snow on its summit, making it the second-highest peak in Africa.

Kenya belongs to the tropical growing region, with two rainy seasons annually, allowing for two harvests. 60% is concentrated from October to December, and the remaining 40% from June to August. Coffee is mainly grown in volcanic soil at altitudes of 1600-2100 meters around the capital Nairobi to the Kenyan mountainous areas. This altitude is suitable for flavor development in coffee beans because the mountain temperatures are lower, growth is slower, and the aromatic components of coffee beans fully develop, with more prominent fruit acidity and harder texture. This crescent-shaped, fertile coffee zone is the main production area for Kenyan specialty beans.

FrontStreet Coffee also often mentions that Arabica coffee beans must have altitude restrictions for growing conditions. The higher the altitude, the better the flavor, and the richer the acidity. This explains why Kenyan coffee is famous for its excellent acidity.

However, Kenya's acidity is completely different from that of neighboring Ethiopian coffee. Coffee enthusiast friends all know that the Ethiopian coffee beans at FrontStreet Coffee are famous for their bright citrus and lemon acidity, while FrontStreet Coffee's Kenyan coffee's acidity is more like cherry tomato acidity. This brings us to the flavor characteristics of its coffee varieties.

Kenya Coffee Bean Varieties

The main varieties grown in Kenya are SL-28, SL-34, Ruiru 11, and Batian. According to FrontStreet Coffee's understanding, these varieties are all products developed by the Kenyan Coffee Research Institute.

SL-28, SL-34

SL actually stands for Scott Labs, Scott Laboratories. In the 1930s, Scott Laboratories was commissioned by the Kenyan government to conduct research on coffee breeding and classification, attempting to find varieties that could adapt to Kenya's terroir, be suitable for large-scale cultivation, and have commercial value. SL-28 and SL-34 are two of many research outcomes. The organization was active from the 1930s to the 1960s but no longer exists today.

The SL series was developed through research and selection based on Yemen Mocha ancient varieties and Bourbon from Réunion Island. Today, they account for the majority of Kenya's coffee production. Relatively speaking, SL-28 has gained higher reputation, while SL-34 has larger yields and is grown at slightly lower altitudes. According to SL Laboratory botanists, SL28 and SL34 are genetic variants. Among them, SL28 has mixed heritage of Mocha and Yemen Typica. The original goal of developing SL28 was to mass-produce coffee beans that combined high quality with resistance to pests and diseases.

Although SL28's yield was not as high as expected later, because of its copper-colored leaves and broad bean shape with wonderful sweetness, balance, and complex changing flavors, as well as significant citrus and plum characteristics, it has been preserved to this day. This is also the main reason why FrontStreet Coffee's Kenyan coffee is rich in pleasant acidity.

SL34 has similar flavors to SL28, but besides the complex and changing acidity and wonderful sweet finish, its body is heavier, richer, and cleaner than SL28. SL34 has Bourbon and more Typica heritage. The bean appearance is similar to SL28, but it can survive better, for example, adapting to sudden heavy rains.

Ruiru 11

Ruiru appeared after SL28 and SL34. According to FrontStreet Coffee's understanding, in the 1970s, the Ruiru station began experimenting with cultivating different CBD and rust-resistant varieties. The result was Ruiru 11, released in the 1980s. High yield, with CBD and rust resistance, this seemed to be the solution to all of Kenya's coffee production problems.

Batian

The Batian variety was launched by the Coffee Research Institute (CRI) on September 8, 2010, and is also the latest variety offered by Kenya. It is a further experiment based on lessons learned from Ruiru 11. Genetically, it is essentially selected from backcrosses of SL28 and SL34, making it closer to SL28 than Ruiru 11. This thus eliminates the problematic Robusta coffee bean elements, thereby improving cupping quality.

Kenya Coffee Bean Grading System

Kenya grades coffee beans by size and cupping results. Based on the size, shape, and hardness of coffee beans, from high to low: AA or AA+, AB, PB, C, E, TT, T. For AA and AB grade raw coffee beans, special grading based on cupping results is added (not officially recognized by Kenyan government, established by exporters), from high to low: TOP, PLUS (+), FAQ.

AA Plus (AA+): Exceptionally excellent AA grade in cup quality (flavor, mouthfeel).

AA: Size (Screen Size) 17-18 mesh.

AB: Size (Screen Size) 15-16 mesh, accounting for the majority of production.

C: Size smaller than AB.

TT: Lighter beans blown out by air screeners from AA and AB grade beans.

T: Lighter beans blown out by air screeners from C grade beans.

E: Elephant Bean: Large variant beans where two beans merge, also called elephant ear.

PB: Peaberry: Classified by shape, unrelated to flavor or weight.

As mentioned by FrontStreet Coffee, whether it's the processing method or growing region and variety, they all have more or less influence on the flavor of coffee beans. Kenya's growing region itself is very suitable for coffee cultivation, and the developed K72 washed processing method further enhances the coffee bean's flavor. The multiple washing also makes the coffee bean flavor cleaner and brighter, which is why Kenyan coffee beans all have flavors similar to the bright fruit acidity of cherry tomatoes.

Next, FrontStreet Coffee will introduce to all coffee enthusiasts the current FrontStreet Coffee Kenyan coffee beans and their roasting and brewing data analysis.

FrontStreet Coffee Kenya Asalia Coffee Beans

Country: Kenya

Region: Asali (Honey Processing Station)

Altitude: 1550-1750m

Varieties: SL28, SL34

Processing: 72-hour washed processing

Flavor: Snow pear, plum, brown sugar, cherry tomato, bramble

FrontStreet Coffee Kenya Asalia Coffee Bean Roasting Record

This FrontStreet Coffee Kenyan bean has a full, round body. To fully express its bright, rich acidity, FrontStreet Coffee uses a light roast. Yangjia 800N semi-direct flame, with 480g beans: enter the drum at 160°C, air damper set to 3, heat at 120. Return temperature: 1'28". When temperature rises to 130°C, open air damper to 4. Roast to 6'00'', temperature 154.6°C, bean surface turns yellow, grassy smell completely disappears, dehydration complete.

When ugly wrinkles and black spots appear on the bean surface, and toast smell clearly changes to coffee aroma, this can be defined as the prelude to first crack. At this time, listen carefully for the sound of first crack. At 9'28'' first crack begins, air damper unchanged, first crack development time 2'20'', drop at 193.8°C.

FrontStreet Coffee Brewing Suggestions

Filter: Hario V60

Water Temperature: 90°C

Coffee Dose: 15g

Ratio: 1:15

Grind Size: Fine sugar (Chinese standard #20 sieve 80% pass-through)

FrontStreet Coffee brewing technique: Use 30g of water for 30-second bloom, pour with small water flow in circles to 125g for segmentation, continue pouring to 225g when water level is about to expose the coffee bed, stop pouring, wait for water level to drop to just before exposing the coffee bed, then remove the filter cup (timing starts from bloom). Extraction time: 2'00".

[FrontStreet Coffee Kenya Asalia] Flavor Description: Wet aroma has mature tomato and floral notes. Entry shows cherry tomato and plum flavors, with bright acidity, clean and rich mouthfeel. Mid-palate has prominent sweetness with juicy sensation. Finish has berry aroma and brown sugar sweetness, with green tea fragrance.

FrontStreet Coffee Kenya Thesini Estate PB Coffee Beans

Country: Kenya

Region: Thesini Estate

Altitude: 1680m

Varieties: SL28, SL34, Ruiru

Processing: 72-hour washed processing

Flavor: Cherry tomato, almond, plum, honey, grape

FrontStreet Coffee Kenya Thesini PB Coffee Bean Roasting Analysis

This rich FrontStreet Coffee Kenyan coffee bean, due to higher altitude, has harder bean density. Start with a higher temperature rise, yellowing point around 5 minutes, then reduce heat to enter Maillard reaction, reduce heat again at 166°C to extend Maillard reaction time. 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 flavor.

Yangjia 800N roaster (300g batch size)

Enter drum at 170°C, heat at 100, air damper set to 3; return temperature 1'42", when drum temperature reaches 140°C open air damper to 3.5, heat unchanged; when drum temperature reaches 149°C, bean surface turns yellow, grassy smell completely disappears, entering dehydration stage;

7'14'' dehydration complete, heat and air damper unchanged, at 7'30'' bean surface shows wrinkles and black spots, toast smell changes to coffee aroma, as prelude to first crack, at this time pay attention to listen for first crack sound. At 8'20'' first crack begins, open air damper to 4, reduce heat to 50. After first crack, development time 1'50'', when reaching 188°C reduce heat to 30, flatten temperature rise, drop at 193.3°C.

FrontStreet Coffee Brewing Suggestions

Filter: V60 or cake filter

Water Temperature: 90-91°C

Ratio: 1:15

Grind Size: Fine grind (Chinese standard #20 sieve 80% pass-through)

Brewing technique: Segmented extraction. Use 30g of water for 30-second bloom, pour with small water flow in circles to 124g for segmentation, continue pouring to 228g when water level is about to expose the coffee bed, stop pouring, wait for water level to drop to just before exposing the coffee bed, then remove the filter cup (timing starts from bloom). Extraction time: 1'55".

[FrontStreet Coffee Kenya Thesini PB] Flavor and Mouthfeel:

When brewed with V60 filter, it smells floral, with cherry tomato, citrus, and nut acidity in the entry. Mid-palate has cream aroma, brown sugar sweetness, with cocoa and oolong tea sensations in the finish. Flavor layers are relatively rich, with prominent floral notes. When brewed with cake filter, it smells of herbal plant aroma and cherry tomato fragrance, with overall juicy sensation and lively acidity.

For more specialty coffee beans, add FrontStreet Coffee's private WeChat: ID: kaixinguoguo0925

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