How Does the Kenya Coffee Grading System Work?
Kenya coffee is graded mainly by bean size and quality, with AA, AB, PB, E, C, TT and T forming the scale used since 1938. AA beans are the largest screen size, AB sits just below, and PB covers peaberry, the single round bean that forms when only one seed develops inside the cherry.
The coffee grading system reflects more than size. Kenyan lots are also sorted for defects and density, and the country's main growing areas, including Nyeri, Kirinyaga and Thika, are known for intense fruity acidity. Most Kenyan coffee comes from smallholder cooperatives, with beans sold through the Nairobi Coffee Exchange auction or direct trade. Varieties such as SL28 and SL34, selected by Scott Laboratories, underpin the flavor.
Kenyan coffee is renowned worldwide for its intense, full-bodied fruity acidity, and its unique flavor profile is inseparable from its strict grading system and refined cultivation and processing systems. This article will systematically review the development of Kenyan coffee, from its introduction during the colonial period, to the Scott Laboratories' selection and breeding of SL28 and SL34, to the grading standards such as AA, AB, and PB established in 1938, explaining one by one the meanings and characteristics of each grade: E, AA, AB, C, PB, TT, and T. At the same time, it will provide an in-depth introduction to the flavor differences among Kenya's main coffee-producing regions such as Nyeri, Kirinyaga, and Thika, analyze the coexistence of large estates and smallholder cooperatives as cultivation models, and the two trading mechanisms of the Nairobi Coffee Exchange auction and direct trade. Front Street Coffee will also share roasting and pour-over recommendations for Kenyan Asalia coffee beans, taking you through a comprehensive understanding of the coffee world of this East African producing country.
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Front Street's Kenyan coffee beans exude a captivating and full aroma, with balanced and pleasant acidity, uniform bean size, and excellent fruit flavor expression. Front Street once compared beans from Kenya with those from neighboring Ethiopia. Although both follow the fruity acidity path, they give completely different impressions—Kenya's acidity is strong and mellow, while Ethiopia's is light and transparent. If you are encountering African coffee for the first time, Front Street suggests starting with Front Street Ethiopian coffee beans and then gradually transitioning to Front Street Kenyan coffee beans.
When it comes to the topic of choosing beans for beginners, many friends consult Front Street about how to choose. Front Street's physical stores in Guangzhou and online Taobao channels both offer the Front Street Daily Beans series, covering seven options: Front Street Ethiopia Yirgacheffe, Front Street Brazil Cerrado, Front Street Colombia Huila, Front Street Indonesia Mandheling, Front Street Costa Rica Tarrazu, Front Street Guatemala Huehuetenango, and Front Street Yunnan small-batch coffee, basically covering the world's major coffee-producing regions. When selecting each "Front Street Daily Bean," Front Street carefully chooses the beans most representative of each region's original local flavor, recommending them to everyone in 100g tasting packs. The original intention of Front Street Daily Beans is to let consumers identify the basic flavors of major producing regions at a relatively low cost, such as the citric acidity of Front Street Yirgacheffe, the herbal notes of Front Street Mandheling, and the nutty chocolate tonality of Front Street Brazil and Front Street Colombia.
The Development History of Kenyan Coffee
Kenya is located in East Africa, adjacent to Ethiopia. However, Kenya's coffee cultivation history is far less long than Ethiopia's, and coffee was not formally introduced until close to the 20th century. When coffee first arrived in Kenya, the area was still a British colony. In order to obtain foreign exchange income, the colonial government promoted coffee cultivation extensively in Kenya, and after harvest shipped the beans to London for export trading. In 1922, Kenya established the Scott Agricultural Laboratories (Scott Labs, from which the names SL28 and SL34 are derived), specializing in coffee cultivation research. Over the more than ten years after the laboratory was established, researchers selected SL28 and SL34, suitable for local growing regions, from 42 coffee varieties, laying a solid foundation for Kenya's coffee industry. To this day, these two varieties still account for 90% of Kenya's planted area.
The Kenyan government places great importance on the coffee sales process. In 1931, the Kenya Planters Cooperative Union and the Kenya National Coffee Board were established one after another, guiding the coffee industry from both civilian and official levels. In 1937, the Nairobi Coffee Exchange was completed, and Kenya's coffee auction system was thereby launched. The concept of good beans commanding good prices established a benchmark for market pricing. In 1938, the Kenyan government promulgated a coffee grading system, namely the well-known grades such as AA, AB, and PB. This system began to provide a basis for judging the quality of Front Street Kenyan coffee.
Kenyan Coffee Cultivation Kenyan coffee is mostly grown in the loose, fertile acidic volcanic red soil of the highlands north and east of Nairobi. This region has abundant sunshine, excellent drainage conditions, and an altitude between 1,400 and 2,000 meters. The higher the altitude, the more pronounced the temperature difference between day and night. Kenya's coffee growing cycle is longer than that of lower-altitude producing regions, so the beans are denser and the flavor is more intense.
Front Street Kenyan coffee usually flowers after rainfall, concentrated in March and April. The coffee cherries mature successively from May to July, and there is another maturation period in September and October, allowing two harvests per year.
Kenyan Coffee Producing Regions Kenya's coffee-producing regions are mainly concentrated in the central and western areas. The central producing regions include Kiambu, Nyeri, Kirinyaga, Muranga, Embu, Machakos, Ruiru, and Thika; the western producing regions include Kisii and the Bungoma area located on Mt. Elgon.
Front Street Coffee regularly updates the coffee-producing regions on its bean list, and Kenya is naturally no exception. Last month, Front Street Coffee introduced a batch of Kenyan coffee beans from different producing regions. After tasting through multiple stages including roasting, cupping, and pour-over, it can be found that each producing region has its own unique characteristics. Kiambu and Muranga are relatively bright and full in acidity. Nyeri presents bright citrus and floral notes. Although slightly inferior compared with Ethiopia's Yirgacheffe, it has a berry-like full-bodied acidity. Kirinyaga's acidity also tends toward bright and full-bodied, accompanied by delicate sweetness. Embu's acidity is not as full-bodied and strong as the previous producing regions, with a more balanced flavor and a long finish. Machakos is also outstanding in acidity, with a delicate mouthfeel and a long aftertaste, and is gradually gaining favor among coffee buyers. The biggest difference between Kisii and the Bungoma area and other producing regions is that they are known for fruity sweetness, with soft acidity and nutty flavors.
Kenyan Coffee Cultivation Models Kenyan coffee consists of two major cultivation entities: large estates, namely more than 3,000 large farms, accounting for about 25% of Kenya's coffee-growing land area. The other 75% belongs to agricultural cooperatives, totaling 270 cooperatives, composed of about 700,000 smallholder farmers. In the 1960s, smallholder cooperatives began building shared processing plants, enabling them to complete coffee harvesting and processing just like large estates. Front Street Coffee believes this model is more conducive to allowing coffee farmers to focus on coffee cultivation and production. Ethiopia's main cultivation model is likewise smallholder cooperatives. A batch of Front Street Yirgacheffe Konga Cooperative coffee beans that Front Street introduced some time ago demonstrated outstanding floral and fruity flavor.
Kenyan Coffee Varieties In Kenya, the common coffee varieties are SL28, SL34, and Ruiru11. In 1922, Kenya established the Scott Agricultural Laboratories (Scott Labs) to conduct coffee cultivation research. Over the following decade or so, the laboratory selected and bred SL28 and SL34, suitable for local cultivation, from 42 coffee varieties, creating a good start for the industry's development. Both SL28 and SL34 are varieties obtained through multiple generations of cultivation and selection. SL28 belongs to the Bourbon genetic group, carrying the bright tonality and rich acidity of original Bourbon. SL34's lineage is closer to the Typica gene, and its acidity is milder than SL28's. At present, SL28 and SL34 together account for 90% of Kenya's output. South America is also actively introducing SL28, and the Asalia coffee that Front Street loves very much is precisely composed of these two numbered varieties.
The birth of Ruiru11 stemmed from the large-scale global outbreak of coffee leaf rust. At that time, many Arabica varieties were attacked by the disease. To avoid reduced coffee production, researchers developed the hybrid variety Ruiru11. It performs excellently in disease resistance, but its flavor quality is far inferior to SL28 and SL34.
Kenyan Coffee Grading System Kenya classifies grades according to coffee bean size and cupping results. According to bean size, shape, and hardness, from high to low, the order is E, AA or AA+, AB, C, PB, TT, T. E (Elephant bean): The "E" here stands for Elephant, but it is not the Maragogype elephant bean among coffee varieties. It is an abnormally developed bean in which two seeds become intertwined with each other, forming a state that "looks like one bean," and it is considered a defect. Normally, a fruit contains two seeds facing each other, so one side is flat, and these are called flat beans or mother beans. Grade E beans are two seeds that fuse and stick together during growth, becoming extraordinarily large. Grade E beans are about 18 screen size (one screen is 1/64 inch) or above, and are rare in number. AA: This grade is about 17–18 screen size (about 6.7–7.1 mm), and is the Kenyan coffee grade most people have heard of most often. In the specialty coffee field, this grade is usually called AA TOP, and it is also the bean type promoted by many coffee shop owners. But AA does not mean the best; it merely reflects bean size and cannot be equated with flavor.
Front Street Coffee Kenyan Sasini Coffee Beans AA Grade
AB: Most coffee beans fall into this grade. It is called AB mainly because A's screen size is 6.80 mm and B's is 6.20 mm. These two sizes of coffee beans (Grade A and Grade B) are sold mixed together, hence the name AB, with a size of about 15–16 screen size (about 6.0–6.4 mm). Front Street Coffee Kenyan Asalia Coffee Beans AA TOP Grade C: Bean size is about 14–15 screen size (about 5.6–6.0 mm), a little smaller than Grade B. PB: The full name is Peaberry, also called small round bean, or male bean. Compared with ordinary flat beans, PB is also relatively rare, accounting for about 10% of all coffee beans. It forms because only one seed develops fully inside the fruit, resulting in a small, round bean. Some people especially prefer the flavor of PB, so it is sorted out separately for sale.
Front Street Coffee Kenyan Sasini Coffee Beans PB Grade
TT: This type of coffee bean is the light bean screened out from AA and AB beans by an airflow separator. It is usually light in weight, fails to meet hardness standards, and has cracks and defects. T: Lighter beans screened out from Grade C beans, mixed with broken beans, and even fragments of shattered beans. There is also another grade, MH/ML: This type of coffee bean is not used for export. It is usually coffee that has fallen to the ground after overripening, of poor quality, accounting for about 7% of all coffee beans, and is only for Kenya's domestic market. For green beans of the AA and AB grades, there is also a special grading that incorporates cupping results (not officially recognized by the Kenyan state, but set by exporters), from high to low: TOP, PLUS (+), FAQ. The flavor level of Front Street Kenyan Asalia on Front Street Coffee's bean list reaches the TOP grade. However, as mentioned earlier, this is not an officially recognized grading system, and several Kenyan producing-region coffee beans introduced by Front Street Coffee do not each carry a flavor grade either, so there is no need to obsess over this point. Generally speaking, reaching the AA and AB grades already means the flavor is by default considered quite high quality.
Front Street Coffee Kenyan Asalia Coffee Beans AA TOP Grade
Kenyan Auction System As Front Street Coffee mentioned earlier, in Kenya's colonial history, local farmers actually did not gain much benefit from the coffee industry, which can be said to be a dark period in Kenya's coffee cultivation history. In 1931, in order to help coffee farmers obtain better prices and income and no longer be constrained by distant traders, the government established the Kenya Planters Cooperative Union and the Kenya National Coffee Board, and established an auction mechanism. In 1937, the Nairobi Coffee Exchange was established. By this time, the auction trading system had become more widespread and had gained broad support.
Most coffee beans are uniformly graded and inspected by the Kenya Coffee Board, and then sold at auction. The public auction system can be traced back to before 1934. The auction adopted an agent system. Kenya had 50 licensed agents responsible for sending sample beans to their respective clients for cupping, and clients could entrust agents to bid at auction for coffees they liked. However, this method seemed to encourage middlemen agents, and instead eroded farmers' income. Therefore, in 2006 Kenya also opened up 32 independent sales agents who could directly contact foreign coffee buyers without going through the auction. However, these still had to meet the Kenya Coffee Board's standards for quality, storage, bank guarantees, and other aspects. The two systems operated in parallel, and after years of development formed an extremely transparent auction distribution system. The better the quality of the coffee, the better the price it could obtain through cupping, thereby attracting more cooperatives and estates to participate. Front Street Coffee also pays close attention to the coffee auction market, which not only helps in understanding changes in the local coffee market, but also means that the improvement of the auction mechanism ultimately benefits not only coffee farmers, but also buyers from around the world.
Two Main Trading Models for Kenyan Coffee Beans ① Nairobi Coffee Exchange auction (central auction system), with about 85% of coffee beans traded through the auction system Since the establishment of the auction system in the 1930s, the vast majority of Kenyan coffee has been traded in this way. Coffee auctions are held every Tuesday during the harvest season. It evolved from an "open outcry" auction system, in which each trader bids by pressing an electronic trigger. Under this system, because agents compete with one another, the prices of high-quality and highly popular coffees soar.
② Direct trade (often called the "second window"), with only about 15% of coffee beans traded through the direct trade model After 2006, the Kenyan government allowed farmers to trade directly with foreign buyers (such as roasters or importers), and a price different from the auction price could be discussed and set before or during the harvest. Some exporters also buy coffee directly from relevant marketing agents or factories, using the previous week's auction price for a specific grade as a reference for negotiation. Direct trade allows farmers producing high-quality coffee to earn more income. When direct trade is not feasible, they return to the exchange for auction sale.
What Kenyan coffee beans does Front Street have? After several rounds of tasting, Front Street Coffee ultimately selects only two or three offerings from the initial dozen or so coffee beans from different producing regions. This is not to say that the quality of the remaining coffee beans is poor. Front Street Coffee's original intention is not simply to sell, but in the process to understand each coffee-producing region, different coffee varieties in the same region, different processing methods for the same variety, and to build a corresponding database, as well as comparisons among different producing regions. Front Street Coffee hopes to let more coffee enthusiasts understand the world of coffee.
Front Street Coffee: Kenya Asalia Coffee Beans
Producing region: Kenya Thika producing region Asali processing plant
Altitude: 1550-1750m
Processing method: Washed
Variety: SL28 & SL34
Flavor: Tomato, snow pear, smoked plum, yellow sugar, plum, cherry tomato
[Roasting Recommendation] This Front Street Kenyan Asalia bean is plump and round. In order to fully display its bright and mellow acidity, Front Street uses a light roast.
[Cupping Flavor]
[Front Street Pour-Over Recommendation] The brewing parameters used by Front Street are: V60 dripper, water temperature 90°C, coffee dose 15 grams, coffee-to-water ratio 1:15, grind size like fine granulated sugar (80% passing through China standard No. 20 sieve). Here Front Street Coffee wants to explain one point: why is sieving needed before determining the grind size? This is actually the grind recommendation given by the Specialty Coffee Association of America (SCA) for pour-over coffee. After extensive verification, Front Street Coffee found that brewing with different grind sizes produces obvious differences in the result, and the grind size for each coffee bean will also differ somewhat, which is precisely the significance of sieving. If you do not have a sieve at home, Front Street Coffee suggests judging by observing the flow rate: if the water flows too fast, the grind is coarse; if the water flows too slowly, the grind is fine.
Front Street Coffee uses staged extraction: first use 30 grams of water for a 30-second bloom, then pour in a small stream in a circular motion until 125 grams, then pause for a stage; when the water level drops and is about to expose the coffee bed, continue pouring until 225 grams and stop; when the water level drops and is about to expose the coffee bed, remove the dripper. (Timing starts at the beginning of the bloom.) The extraction time is 2'00".
[Front Street Kenyan Asalia Coffee Bean Flavor] The wet aroma carries ripe tomato and floral notes. On the palate, it presents flavors of cherry tomato and smoked plum, with bright acidity, a clean and rich mouthfeel, and outstanding sweetness in the middle section with a juicy sensation. The finish is berry aroma and yellow sugar sweetness, accompanied by green tea fragrance.
The above content is compiled by CoffeeHunters, a coffee news website.
