How Does the Kenya Coffee Grading System Work?

Kenya grades coffee largely by bean size, with AA, AB, and PB as the familiar screen sizes. AA TOP is not a separate official grade but a designation used to flag lots that also cup well. A large screen size alone does not guarantee quality, so the cup profile still decides whether a lot earns the top label.

Kenya's coffee history shapes that system. The Scott Agricultural Laboratories, founded in 1922, selected SL28 and SL34 from 42 varieties, and those two still cover about 90 percent of planted area. Coffee arrived under British colonial rule and was shipped to London for auction. Kenya's acidity reads intense and heavy next to Ethiopia's softer, more transparent cup.

Kenyan coffee is renowned worldwide for its bright, intense fruit acidity and full, robust body, yet its grading system—AA, AB, PB, and so on—often confuses enthusiasts. What exactly is the difference between AA and AA TOP? Does the grading standard consider only bean size, or also cup profile? This article traces Kenya's coffee history, growing conditions, variety selection, regional characteristics, the grading system, and the auction trading model, and combines tasting examples from several Front Street Coffee Kenyan beans to help readers clarify the real difference between AA and AA TOP.

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Front Street's Kenyan coffee beans have an amazing aroma, balanced and pleasant acidity, uniform bean size, and excellent fruit flavor expression. Front Street once compared Kenyan beans with beans from neighboring Ethiopia. Although both follow the fruit acidity route, they give completely different impressions—Kenya's acidity tends toward intensity and heaviness, while Ethiopia's acidity is softer and more transparent. If you are trying African coffee beans for the first time, Front Street suggests starting with Ethiopian beans and gradually transitioning to Kenyan beans.

The Development History of Kenyan Coffee

Kenya is located in East Africa, adjacent to Ethiopia. Compared with Ethiopia's long coffee tradition, Kenya introduced coffee much later, not beginning cultivation until close to the 20th century. When coffee first arrived, Kenya was still under British colonial rule. In order to obtain foreign exchange income, the colonial government vigorously promoted coffee cultivation locally, and after harvest the coffee was uniformly shipped to London for export trading. In 1922, Kenya established the Scott Agricultural Laboratories (Scott Labs, from which the names SL28 and SL34 come), specializing in coffee cultivation research. Over the following decade or so, researchers selected SL28 and SL34 from 42 coffee varieties as suitable for local growing regions, laying a good foundation for Kenya's coffee industry. To this day, these two varieties still account for 90% of Kenya's planted area.

The Kenyan government attached great importance to the coffee sales process. In 1931, the Kenya Planters Cooperative Union and the Kenya National Coffee Board were established one after another, guiding the development of the coffee industry from both civic and official levels. In 1937, the Nairobi Coffee Exchange was completed, and Kenya's coffee auction system was launched. Good coffee could sell for a good price, setting a benchmark for industry pricing. In 1938, the Kenyan government promulgated a coffee grading system, namely the familiar AA, AB, PB and other grades. This system provided the basis for judging the quality of Front Street Kenyan coffee.

Kenyan Coffee Cultivation Kenyan coffee is mostly grown in the acidic volcanic red soil of the highlands north and east of Nairobi, where the soil is fertile and loose. This region has abundant sunshine, excellent drainage, and an altitude between 1,400 and 2,000 meters. The higher the altitude, the greater the temperature difference between day and night, and the longer the ripening cycle of the coffee fruit than in low-altitude producing areas, so the beans are denser and the flavor is more intense.

Front Street Kenyan coffee usually flowers after rainfall, with the flowering period concentrated in March and April. Coffee cherries mature successively from May to July, and there is another maturity period in September and October, allowing two harvests per year.

Kenyan Coffee Producing Regions Kenyan coffee producing regions are mainly distributed in the central and western areas. The central producing regions include Kiambu, Nyeri, Kirinyaga, Muranga, Embu, Machakos, Ruiru, and Thika; in the west there are Kisii and the Bungoma area located on Mt. Elgon.

Front Street Coffee (FrontStreet Coffee) regularly updates the coffee producing regions on its bean list, and Kenya is naturally no exception. Last month Front Street Coffee (FrontStreet Coffee) introduced a batch of Kenyan beans from different producing regions. After tasting them through roasting, cupping, pour-over, and other stages, it was clear that each producing region has its own strengths. The acidity of Kiambu and Muranga is relatively bright and full. Nyeri carries bright citrus and floral notes. Although slightly inferior to Ethiopia's Yirgacheffe, it excels with a thick, berry-like acidity. Kirinyaga's acidity is likewise on the bright and heavy side, accompanied by a delicate sweetness. The acidity of Embu is not as strong and full as the previous producing regions, and the flavor tends to be more balanced with a lasting aftertaste. Machakos also has prominent acidity, a delicate mouthfeel, and a long finish, and is gradually winning the favor of coffee buyers. The biggest difference between Kisii and Bungoma and other producing regions is that they are known for fruit sweetness, with soft acidity and nutty notes.

Kenyan Coffee Cultivation Models Kenyan coffee consists of two major cultivation systems: first, large estates, with more than 3,000 large farms nationwide, accounting for about 25% of the coffee-growing land area; second, agricultural cooperatives, with 270 cooperatives in total, composed of about 700,000 smallholder farmers, occupying the remaining 75%. Starting 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 (FrontStreet Coffee) believes that this model allows coffee farmers to focus more on cultivation and production. Ethiopia's main cultivation model is likewise smallholder cooperatives. A batch of Front Street Yirgacheffe Konga Cooperative coffee beans introduced by Front Street some time ago displayed outstanding floral and fruity flavors.

Kenyan Coffee Varieties Common Kenyan coffee varieties include SL28, SL34, and Ruiru11. In 1922, Kenya established the Scott Agricultural Laboratories (Scott Labs) to engage in coffee cultivation research, and over more than a decade selected SL28 and SL34 from 42 coffee varieties as suitable for local cultivation, giving the industry a good start. Both varieties were developed through multiple generations of cultivation and selection. SL28 belongs to the Bourbon genetic group, with the bright profile and rich acidity of original Bourbon; SL34's lineage is closer to Typica, and its acidity is gentler than SL28's. At present, SL28 and SL34 together account for 90% of Kenya's production, and South America is also actively introducing SL28. The Asalia coffee that Front Street loves so much is precisely composed of these two varieties.

The birth of Ruiru11 stemmed from the global outbreak of coffee leaf rust. At that time, a large number of Arabica varieties were attacked by the disease. To preserve 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 based on coffee bean size and cupping results, from high to low as E, AA or AA+, AB, C, PB, TT, and T. E (Elephant bean): Here the "E" stands for Elephant, but it is not the elephant bean (Maragogype) among coffee varieties. Rather, it is an abnormally developed bean—two seeds intertwined with each other, forming a shape that "looks like one bean," essentially a defect. Normally, a fruit contains two seeds fitted face to face, so one side is flat, and these are called flat beans or female beans. Grade E beans are two seeds that have adhered together during growth, becoming abnormally large. Grade E beans are about 18 screen size (one screen is 1/64 inch) or above, and are extremely rare in number. AA: This grade is about 17 to 18 screen size (about 6.7 to 7.1 mm), and is the Kenyan coffee grade most people have heard of most often. In the specialty coffee world, this grade is usually called AA TOP, and it is also the bean that many coffee shops strongly promote. But AA does not mean the best; bean size ultimately cannot be equated with flavor.

Front Street Coffee (FrontStreet Coffee) Kenya Sasini Coffee Beans AA Grade

AB: Most coffee beans fall into this grade. It is called AB because A's screen size is 6.80 mm and B's is 6.20 mm, and beans of these two sizes (Grade A and Grade B) are sold mixed together, hence the name AB, about 15 to 16 screen size (about 6.0 to 6.4 mm). Front Street Coffee (FrontStreet Coffee) Kenya Asalia Coffee Beans AA TOP Grade C: Bean size is about 14 to 15 screen size (about 5.6 to 6.0 mm), smaller than Grade B. PB: Full name Peaberry, also called small round bean, or male bean. Compared with ordinary flat beans, this kind of bean is 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 particularly prefer the flavor of PB, so it is sorted out and sold separately.

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

TT: This type of coffee bean is the light bean screened out from AA and AB by an air separator, usually light in weight, failing to meet hardness standards, and with cracks and defects. T: Lighter beans screened out from Grade C beans, mixed with broken beans and even shattered fragments. There are also MH/ML grades: these coffee beans are not used for export and are usually overripe beans that have fallen to the ground. Their quality is poor, accounting for about 7% of all coffee beans, and they are only supplied to Kenya's domestic market. For green coffee beans of Grade AA and Grade AB, exporters also add a special grading based on cupping results (not officially recognized by Kenya), from high to low as TOP, PLUS (+), and FAQ. The flavor level of Front Street Kenya Asalia on the Front Street Coffee (FrontStreet Coffee) bean list reaches the TOP grade. However, as mentioned earlier, this is not an officially recognized grading system. Among the several Kenyan producing-region coffees introduced by Front Street Coffee (FrontStreet Coffee), not every one carries a flavor grade, so there is no need to obsess over this point. Generally speaking, once beans reach Grade AA and Grade AB, their flavor is in fact already considered quite high quality by default.

Front Street Coffee (FrontStreet Coffee) Kenya Asalia Coffee Beans AA TOP Grade

Kenyan Auction System Front Street Coffee (FrontStreet Coffee) mentioned earlier that during colonial rule, local farmers did not gain much benefit from the coffee industry, which counts as a dark period in the history of Kenyan coffee cultivation. In 1931, in order to help coffee farmers obtain better selling 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 set up 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, and Kenya had 50 licensed agents who sent sample beans to their respective clients for cupping. Clients could entrust agents to bid at auction for the coffees they liked. But this method seemed to encourage intermediary agents and instead eroded farmers' income. Therefore, in 2006 Kenya opened up 32 independent sales agents who could directly contact foreign coffee buyers without going through the auction. However, all of this must meet the Kenya Coffee Board's standards for quality, storage, bank guarantees, and so on before it can proceed. The two systems operated in parallel at the same time. After years of development, they formed an extremely transparent auction allocation system. The better the quality of the coffee, the better the price it can obtain through cupping, which also makes more cooperatives and estates willing to participate. Front Street Coffee (FrontStreet Coffee) also pays close attention to the coffee auction market. This not only helps in understanding changes in the local coffee market, but 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 auction system was established 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 bid by pressing an electric trigger. In this system, because agents compete with one another, prices for high-quality, highly popular coffee can soar.

② Direct trade (often called the "second window"), with only about 15% of coffee beans traded through this 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 agreed upon before or during harvest. Some exporters also buy coffee directly from the relevant marketing agents or factories, using the previous week's auction prices for a specific grade as the negotiation benchmark. 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 (FrontStreet Coffee) ultimately lists only two or three out of the initial dozen or so coffee beans from different producing regions. This is not to say the quality of the remaining beans is poor. Front Street Coffee's (FrontStreet Coffee) original intention is not simply to sell, but through this process to understand each coffee producing region, different varieties in the same producing region, different processing methods for the same variety, and to build a corresponding database, as well as comparisons between different producing regions. Front Street Coffee (FrontStreet Coffee) hopes to help more coffee lovers understand the world of coffee.

Front Street Coffee (FrontStreet Coffee): Kenya Little Tomato 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 Suggestion] This Front Street Kenya Little Tomato bean is plump and round. In order to fully display its bright, mellow acidity, Front Street uses a light roast.

[Cupping Flavor]

[Front Street Pour-over Suggestion] The brewing parameters used by Front Street are: V60 dripper, water temperature 90°C, coffee dose 15 g, coffee-to-water ratio 1:15, grind size fine sugar granule size (80% passing through China standard No. 20 sieve). Here Front Street Coffee (FrontStreet Coffee) should explain one point: why sieving is needed before determining grind size. This is actually the grind recommendation provided by the Specialty Coffee Association of America, SCA, for pour-over coffee. After extensive verification, Front Street Coffee (FrontStreet Coffee) found that brewing with different grind sizes produces obvious differences in the final cup, and the grind size for each coffee bean is somewhat different. This is precisely the meaning of sieving. If you do not have a sieve at home, Front Street Coffee (FrontStreet 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 (FrontStreet Coffee) uses staged extraction: bloom with 30 g of water for 30 seconds, then pour in a small stream in circles until 125 g for a stage break. When the water level drops and is about to expose the coffee bed, continue pouring until 225 g and stop. When the water level drops and is about to expose the coffee bed, remove the dripper. The extraction time (starting from the beginning of blooming) is 2'00".

[Front Street Kenya Asalia Coffee Bean Flavor] The wet aroma has ripe tomato and floral notes. On the palate it presents cherry tomato and smoked plum flavors, with bright acidity, a clean and rich mouthfeel, a prominent sweetness in the middle, and a juicy quality. The aftertaste is berry aroma and yellow sugar sweetness, accompanied by green tea aroma.

Front Street Coffee (FrontStreet Coffee): Kenya·Sasini Estate PB Coffee Beans Producing region: Kiambu producing region Estate: Sasini Estate Altitude: 1680 meters Grade: PB Variety: SL28, SL34 & Ruiru Processing method: Washed processing

[Roasting Suggestion] Front Street Coffee (FrontStreet Coffee) uses a light roast. As mentioned earlier, the overall flavor of Kenyan coffee beans is mainly a bright acidity profile. To emphasize this point, Front Street Coffee (FrontStreet Coffee) suggests making appropriate adjustments in the direction of a light roast.

[Cupping Flavor]

[Front Street Pour-over Suggestion] The brewing parameters used by Front Street are: V60 dripper, water temperature 90°C, coffee dose 15 g, coffee-to-water ratio 1:15, grind size BG#5I (80% passing through China standard No. 20 sieve). Perhaps sharp-eyed readers will notice that Front Street Coffee's (FrontStreet Coffee) grind parameter for this Kenyan bean differs from the other bean earlier. The grind size for each coffee bean will be different because factors such as variety, altitude, processing method, and roasting vary. Therefore, when Front Street Coffee (FrontStreet Coffee) receives a newly roasted bean, it first sieves it once to determine the appropriate pour-over grind size.

Front Street uses staged extraction: bloom with 30 g of water for 30 seconds, then pour in a small stream in circles until 125 g for a stage break. When the water level drops and is about to expose the coffee bed, continue pouring until 225 g and stop. When the water level drops and is about to expose the coffee bed, remove the dripper. The extraction time (starting from the beginning of blooming) is 2'00".

[Front Street Kenya Sasini Coffee Bean Flavor] Obvious smoked plum and cherry tomato flavors, almond in the middle, honey in the finish, a juicy mouthfeel, and bright acidity. The Difference Between Front Street Kenya AA and Kenya PB In fact, it is not hard to see that these two Front Street beans have obvious differences in grade classification, and the roasting parameters and brewing parameters used by Front Street are also different. Under these conditions, differences can also be perceived in their flavor presentation.

What the two have in common is that both have obvious smoked plum, cherry tomato, and honey flavors. As the temperature drops, they bring out slight nutty notes, a juicy mouthfeel, and bright acidity. But AA's acidity is brighter than PB's, and its overall layering is richer; PB highlights the sweetness of berries and honey, and is overall clean and soft.

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