What do Kenya coffee bean grades like AA really tell you?

Kenya AA and AB are coffee bean grades based on screen size, not flavor quality. Front Street argues the Kenyan baseline is a thick, juice-like mouthfeel rather than the tomato note many drinkers expect. Auction lots place more weight on cupping performance, and specialty Kenyan coffee consistently fetches high prices because of it. Size grading and cup score measure different things, so neither replaces the other.

Kenya grows coffee mostly between 1,500 and 2,100 meters, and the K72 washed coffee bean process, with its long fermentation and soaking, shapes the dense texture. Cupping two lots, Nyeri Gathaithi AB and Mugaya AB, shows that acidity and flavor direction still vary by region and harvest year even when both come from the same country and processing method.

Kenya AA coffee beans have always been a hot topic in the specialty coffee circle. Many people's impression of Kenyan beans stops at the small tomato flavor, but Front Street believes that the core characteristic of the Kenyan region should be a thick, full-bodied juice-like mouthfeel. This article will unfold from aspects such as Kenya's coffee trade system, grading standards, six major regions, variety characteristics, and the K72 washed processing method, and through Front Street Coffee's comparison of roasting, cupping, and brewing of two beans—Nyeri Gathaithi AB and Mugaya AB—take you to a deeper understanding of the true character of Kenyan coffee, and explain the meaning of the AA grade and FAQ cupping quality.

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When many coffee lovers mention Kenyan coffee beans, their first reaction is a small tomato-like flavor, and some even insist that without this tomato note it cannot be considered Kenyan coffee. Front Street does not agree with defining beans from the Kenyan region by a single flavor. The original flavor baseline of Kenyan coffee should be that solid, full-bodied texture like freshly squeezed juice.

For any plant, the soil and climate of its growing environment profoundly affect its development, and coffee trees are naturally no exception. Changes in factors such as regional climate and soil conditions will cause coffee beans from different harvest years to differ in flavor. Front Street has cupped several Kenyan coffees in recent months and found that no matter which region they come from, they all present a substantial juice-like quality; of course, they are not completely identical, and the acidity and flavor direction still differ from one another.

Kenya is a renowned coffee-producing country in East Africa and an important source of specialty coffee worldwide. Kenyan coffee is rich in flavor and distinctive in character, and its trade methods have also developed into a sophisticated system. The AA or AB grades divided by bean size cannot directly equate to flavor quality; the coffee board's auction lots place more emphasis on cupping performance, and the auction prices of specialty Kenyan coffee have always remained at a relatively high level. Kenyan coffee is mostly grown at altitudes of 1,500 to 2,100 meters and can be harvested twice a year. To ensure that only ripe cherries are picked, people must repeatedly patrol the trees, going back and forth about seven times.

Kenya has two coffee sales systems: one is the auction held at the Nairobi Coffee Exchange (the central auction system), through which about 85% of coffee beans are traded; the other is direct trade (often called the "second window"), through which only 15% of coffee beans circulate.

The Nairobi Coffee Exchange is the venue for Kenya's coffee auction trade. Auctions are currently held once every two weeks, with bidding fixed on Tuesdays. Twelve days before bidding begins, market agents send green bean samples to the NCE for display, giving buyers ample time to select suitable items for cupping. Each auction has about several hundred beans, sometimes even more than a thousand, and the whole process lasts almost an entire day, from 9:30 in the morning until four or five in the afternoon, without interruption. Dozens of buyers in the hall bury themselves in the green bean catalog, bidding while constantly recording the transaction price of each green bean.

The current Kenyan coffee industry chain is roughly as follows: after coffee farmers harvest the cherries, they send them to washing stations, where preliminary density grading is carried out, and then they are handed over to market agents. At the washing station stage, coffee beans are already graded by screen size into the familiar AA, AB, PB, C, etc., and then green bean samples are passed to the NCE to participate in the auction and provide a catalog. At the auction, buyers bid for the green beans that meet their needs, and finally they are exported abroad. From this perspective, the NCE is in the middle of the entire industry chain, playing the role of an auction platform.

Kenyan coffee bean grades AA Plus (AA+): AA grade with particularly excellent cup quality (flavor, mouthfeel). AA screen size: 17-18 mesh. AB screen size: 15-16 mesh, accounting for most of production. C screen size: smaller than AB. TT: lighter beans blown out from AA and AB grade beans by an airflow separator. T: lighter beans blown out from C grade beans by an airflow separator. E Elephant Bean: a large mutant bean formed by two beans joined together, also called elephant ear. PB Peaberry: classified by appearance, unrelated to flavor or weight. The Kenyan coffee regions are mainly six major regions including: Thika, Kirinyaga, Mt. Kenya West, Nyeri, Kiambu, and Muranga. The harvest periods of the six major regions are October to December (main crop season) and June to August (fly crop season) each year. Among them, Nyeri and Kirinyaga are the most famous.

Nyeri is located in the high mountain area near Mount Kenya and is an important producing region for Kenya's specialty-grade coffee, with an average altitude of more than 1,500 meters. Many high-quality Kenyan coffees come from here. Nyeri is sufficiently high in altitude and lies east of the Aberdare Range, while also being on the promontory between Mount Kenya and the main mountain. With its high terrain and fertile soil, Nyeri has become a major coffee town in central Kenya, and related industry facilities are also quite developed.

The Kirinyaga producing region is located on the slopes of Mount Kenya, at an altitude of 1,300 to 1,900 meters. It is adjacent to the Nyeri producing region and is world-renowned for coffee with strong flavor, rich layers, and a solid mouthfeel. Together with Nyeri, it is regarded as one of the two currently finest producing regions in Kenya.

Coffee bean varieties

SL28 is a single variety selected in 1935 from a drought-resistant population of the Tanganyika variety. SL28 is suitable for planting at medium and high altitudes and has drought resistance, but it is very sensitive to the main coffee diseases. The bean appearance of SL28 is close to the Bourbon variety, round-bodied and thick, and genetic testing in recent years has also confirmed that SL28 belongs to the Bourbon genetic group.

SL34 was first selected in the late 1930s at Kenya's Scott Agricultural Laboratories. SL34 was selected from a tree on the Kabete Loresho estate in Kenya, and this tree was called "French Mission." The bean appearance of SL34 is close to the Typica variety. Front Street screened out beans from Kenyan coffee that were close to Typica in appearance, with elongated bodies, oval shape, and a relatively flat look from the side. Genetic testing in recent years indicates that SL34 is related to the Typica genome.

Coffee bean processing methods

Generally speaking, the washed processing method for coffee beans is to first remove the peel and pulp of the coffee cherry, leaving only a thin layer of mucilage for washed fermentation for 24 to 48 hours, and finally drying by machine or sun. The Kenyan-style washed processing, however, is different: the entire fermentation process reaches 72 hours.

The Kenyan-style washed processing adopts a repeated cycle of washing after fermentation: on the day of harvest, the highest-quality cherries are selected, depulped, and fermented for 24 hours, then washed with clean river water after 24 hours. Next, they are fermented again with clean river water for 24 hours and washed again, repeating this cycle 3 times to reach 72 hours, so it is called the Kenyan-style 72-hour fermentation washed processing method, or K72 for short. Front Street believes that this processing method allows the coffee beans to ferment for a long time at low temperatures, enabling the beans to have a brighter, cleaner yet fuller flavor.

Next, Front Street Coffee (FrontStreet Coffee) compares the coffee beans from the two producing regions through roasting, cupping, and brewing to see what differences there are in flavor.

Front Street Coffee (FrontStreet Coffee) — Kenya Gathaithi Cooperative AB coffee beans

Region: Kenya Nyeri Gathaithi Cooperative

Washing station: Gathaithi Washing Station

Altitude: 1825m

Variety: SL28 & SL34

Processing method: K72 washed

Front Street Coffee (FrontStreet Coffee) — Kenya Mugaya AB coffee beans

Region: Kenya Mugaya Washing Station

Altitude: 1400m

Variety: SL28 & SL34

Processing method: K72 washed

Harvest season: 2020

Front Street Coffee (FrontStreet Coffee) roasting record Gathaithi coffee beans Roasting: Front Street's roaster used a Yangjia 800N semi-direct fire, with a charge of 480g. The drum temperature was 165°C when the beans were charged, the damper was set to 3, and the heat was 120. Turning point: 1'28". When the temperature rose to 140°C, the damper was set to 4. Roasted to 6'00'', temperature 153°C, the bean surface turned yellow, the grassy smell completely disappeared, and dehydration was complete. When ugly wrinkles and dark spots appear on the bean surface and the toast smell clearly turns into coffee aroma, it can be defined as the prelude to first crack. At this time, you must listen clearly to the sound of the first crack point. At 9'17'' first crack began, the damper remained unchanged, the heat was lowered to 90 at 188°C, first crack development time was 2'00'', and the beans were dropped at 193.5°C.

Mugaya coffee beans Roasting: Front Street's roaster used a Yangjia 800N semi-direct fire, with a charge of 480g. The drum temperature was 160°C when the beans were charged, the damper was set to 3, and the heat was 120. Turning point: 1'28". When the temperature rose to 130°C, the damper was set to 4. Roasted to 6'00'', temperature 154.6°C, the bean surface turned yellow, the grassy smell completely disappeared, and dehydration was complete. When ugly wrinkles and dark spots appear on the bean surface and the toast smell clearly turns into coffee aroma, it can be defined as the prelude to first crack. At this time, you must listen clearly to the sound of the first crack point. At 9'28'' first crack began, the damper remained unchanged, first crack development time was 2'20'', and the beans were dropped at 193.8°C.

Front Street Coffee (FrontStreet Coffee) cupping report

Front Street Coffee (FrontStreet Coffee) conducts cupping within 8-24 hours after the sample coffee beans are roasted. The cupping bowl generally used by Front Street Coffee (FrontStreet Coffee) baristas is a 200ml ceramic bowl. The water temperature used for cupping is 94°C. The grind size is controlled so that the passing rate through a No. 20 standard sieve (0.85 mm) is 70%-75%. Ratio: 11 grams of coffee grounds plus 200 milliliters of hot water, that is, 1:18.18, so that the extracted concentration falls exactly within the golden cup range of 1.15%-1.35%, and the steeping time is 4 minutes.

Gathaithi coffee bean dry aroma: citrus; wet aroma: plum; flavor: citrus, plum, berries, honey, grape, tea-like. Mugaya coffee Bean dry aroma: berries; wet aroma: caramel; flavor: smoked plum, plum, grape, caramel, nuts. From cupping the two beans, we can notice that the slightly higher-altitude Gathaithi coffee beans have richer acidity, because the large temperature difference between day and night caused by high altitude slows the growth of coffee trees, giving more time for coffee flavor formation.

Front Street Coffee (FrontStreet Coffee) brewing notes

Dripper: V60 #01 Water temperature: 90°C Dose: 15g Coffee-to-water ratio: 1:16 Grind size: medium-fine grind (screened through a No. 20 sieve to 77%)

Front Street brewing method: first wet the filter paper and preheat the dripper and coffee pot. Use 30 grams of water for a 30-second bloom, pour in a small stream in circles until 130 grams and then divide the pour; when the water level drops and is about to expose the coffee bed, continue pouring until 240 grams and stop pouring; when the water level drops and is about to expose the coffee bed, remove the dripper, (start timing at the beginning of the bloom), with an extraction time of 2 minutes.

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