Kenyan Coffee Bean Grading System: What's the Difference Between Kenya AA TOP and Kenya AA Coffee Beans

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FrontStreet Coffee's Kenya coffee beans possess wonderful and satisfying aromas, balanced and pleasant acidity, uniform particles, and excellent fruit flavors. FrontStreet Coffee has compared Kenya's coffee beans with those from neighboring Ethiopia, finding that although both feature fruity acidity profiles, their presentations are completely different. Kenya's acidity is strong and full-bodied, while Ethiopia's acidity is light and bright. For those trying African coffee beans for the first time, FrontStreet Coffee suggests starting with FrontStreet Coffee's Ethiopian coffee beans before gradually transitioning to FrontStreet Coffee's Kenyan coffee beans.

The Development History of Kenyan Coffee

Kenya is located in East Africa, bordering Ethiopia. Kenya's coffee history is not as ancient as Ethiopia's, with coffee only being introduced around the turn of the 20th century. When coffee was first introduced to Kenya, the country was under British colonial rule. At that time, the British colonial government widely promoted coffee cultivation to earn foreign exchange, exporting harvested coffee beans to London for sale.

In 1922, Kenya established the Scott Agricultural Laboratory (SL28 and SL34 derive their names from this institution) to conduct coffee cultivation research. In the decade following its establishment, they selected SL28 and SL34 from 42 coffee varieties as most suitable for cultivation in the region, providing an excellent beginning for coffee industry development. Today, these two varieties occupy 90% of Kenya's cultivation area.

The Kenyan government places great importance on coffee sales. In 1931, the Kenya Growers Cooperative Union and the Kenya National Coffee Committee were established to guide coffee industry development from both civilian and national levels. In 1937, the Nairobi Coffee Exchange was established, initiating Kenya's coffee auction system where good coffee commands good prices, setting the tone for coffee pricing. In 1938, the Kenyan government released a coffee grading system, which we know as AA, AB, PB, establishing a basis for FrontStreet Coffee's Kenyan coffee quality.

Kenyan Coffee Cultivation

Most Kenyan coffee grows in the fertile, loose acidic volcanic red soil of the highlands north and east of Nairobi. This area enjoys abundant sunlight and good drainage, with elevations between 1,400-2,000 meters. Due to greater temperature variations at higher altitudes, Kenyan coffee has a longer maturation period than coffee from lower altitude regions, resulting in higher density and richer flavors.

FrontStreet Coffee's Kenyan coffee typically flowers after rainfall, which occurs in March and April. Coffee cherries (fruit) mature from May to July and then again from September to October, allowing for two harvest seasons per year.

Kenyan Coffee Growing Regions

Kenya's coffee growing regions are mainly distributed in the central and western parts of the country. Major coffee growing regions in the central area include Kiambu, Nyeri, Kirinyaga, Muranga, Embu, Machakos, Ruiri, and Thika. In the western region, there's Kisii and Bungoma district located on Mount Elgon.

FrontStreet Coffee periodically updates the coffee growing regions on its bean menu, and Kenya is no exception. Last month, FrontStreet Coffee sourced a batch of Kenyan coffee beans from different growing regions. Through multiple stages of roasting, cupping, and pour-over tasting, we found that each region has its unique characteristics.

Kiambu and Muranga show brighter and fuller acidity in their expression.

Nyeri features bright citrus and floral aromas, which, while slightly inferior to Ethiopia's Yirgacheffe, carries rich berry acidity.

Kirinyaga's acidity also tends toward brightness and fullness, with delicate sweetness.

Embu's acidity expression is not as full and strong as the previous regions, with balanced flavors and persistent aftertaste.

Machakos also shows outstanding acidity, with delicate mouthfeel and persistent finish, gradually gaining attention from coffee buyers.

Kisii and Bungoma's greatest difference from other regions is their prominent fruit sweetness, gentle acidity, and nutty flavors.

Kenyan Coffee Cultivation Models

Kenyan coffee comes from two main cultivation types: large plantations, with over 3,000 large farms accounting for approximately 25% of Kenya's coffee cultivation land. The remaining 75% consists of agricultural cooperatives, comprising 270 cooperatives formed by 700,000 small-scale farmers.

In the 1960s, smallholder cooperatives began developing shared processing facilities, enabling them to handle coffee harvesting and processing like large plantations. FrontStreet Coffee believes this model allows coffee farmers to focus more on coffee cultivation and production. Ethiopia's main coffee cultivation model also uses smallholder cooperatives. A batch of FrontStreet Coffee's Yirgacheffe Konga cooperative coffee beans sourced earlier demonstrated excellent floral and fruit flavors.

Kenyan Coffee Varieties

In Kenya, common coffee varieties include SL28, SL34, and Ruiru 11.

In 1922, Kenya established the Scott Agricultural Laboratory to conduct coffee cultivation research. In the decade following its establishment, the laboratory selected SL28 and SL34 from 42 coffee varieties as most suitable for cultivation in the region, providing a good start for coffee industry development. Both SL28 and SL34 are varieties selected after multiple breeding cycles. SL28 belongs to the Bourbon genetic group, carrying the bright acidity and rich complexity of original Bourbon. SL34's lineage is closer to Typica genetics, with gentler acidity than SL28. SL28 and SL34 currently account for 90% of Kenya's production. South America is also actively introducing SL28 as a cultivation variety, and the Assalia coffee that FrontStreet Coffee particularly enjoys is composed of these two numbered varieties.

Ruiru 11 was born out of the global coffee leaf rust outbreak. At that time, many Arabica varieties suffered from disease. To prevent coffee production reduction, the hybrid variety Ruiru 11 was developed, showing excellent disease resistance but with flavor quality far inferior to SL28 and SL34.

Kenyan Coffee Grading System

Kenya grades coffee based on bean size and cupping results. According to coffee bean size, shape, and hardness, from highest to lowest: E, AA or AA+, AB, C, PB, TT, T.

E (Elephant Bean): Here "E" represents Elephant, but this is not the Maragogype elephant bean variety. It's a developmental abnormality where two seeds intertwine, forming what appears to be a single bean, considered a defect. Generally, one fruit contains two seeds facing each other, resulting in one flat side called flat beans or female beans. E-grade beans are two seeds that fuse together during growth, becoming oversized beans. E-grade beans are about 18 screen (one screen = 1/64 inch) or larger and are rare.

AA: This grade typically falls between 17-18 screen (approximately 6.7-7.1mm), the most commonly heard Kenyan coffee grading. In specialty coffee, this grade is usually called AA TOP and is promoted by many coffee shops, but AA doesn't necessarily represent the best - this only indicates bean size and shouldn't be confused with flavor.

FrontStreet Coffee's Kenya Sasini Coffee Beans - AA Grade

AB: Most coffee beans fall in this grade. It's called AB mainly because A-size beans are 6.80mm and B-size are 6.20mm, and these two sizes (A-grade and B-grade) are mixed and sold together, hence called AB, approximately 15-16 screen (about 6.0-6.4mm). FrontStreet Coffee's Kenya Assalia Coffee Beans - AA TOP Grade

C: Bean size approximately 14-15 screen (about 5.6-6.0mm), slightly smaller than B-grade.

PB: Full name Peaberry, also called small round beans or male beans. Compared to regular flat beans, these are also rare, accounting for about 10% of all coffee beans, mainly because only one seed develops inside the fruit, resulting in small, round beans. Some people particularly appreciate PB flavors, so they are separated and sold.

FrontStreet Coffee's Kenya Sasini Coffee Beans - PB Grade

TT: These coffee beans are lightweight beans selected from AA and AB beans through air sorters, typically light in weight and below standard hardness, often including broken and defective beans.

T: Lightweight beans selected from C-grade beans, including damaged and broken bean fragments.

Additionally, there's MH/ML grade: These coffee beans are not exported, typically overripe beans that have fallen to the ground with poor quality, accounting for about 7% of all coffee beans, serving only Kenya's domestic market.

For AA and AB grade green coffee beans, special grading based on cupping results has been added (not officially recognized by Kenyan government, established by exporters), from highest to lowest: TOP, PLUS (+), FAQ. The flavor grade of FrontStreet Coffee's Kenya Assalia on the menu reaches TOP grade. However, as mentioned earlier, this is not an officially recognized grading system. Not every batch of Kenyan coffee beans sourced by FrontStreet Coffee carries flavor grading, so don't dwell too much on this aspect. Generally, reaching AA and AB grades already implies very high quality in flavor.

FrontStreet Coffee's Kenya Assalia Coffee Beans - AA TOP Grade

Kenyan Auction System

As FrontStreet Coffee mentioned earlier, during Kenya's colonial history, local farmers didn't benefit much from coffee, which can be considered a dark moment in Kenyan coffee cultivation history. In 1931, to help farmers achieve better prices and income without being controlled by distant traders, the government established the Kenya Growers Cooperative Union and the Kenya National Coffee Committee, creating an auction mechanism. In 1937, the Nairobi Coffee Exchange was established, when the auction trading system had become more widespread and widely supported.

Most coffee beans are uniformly graded and inspected by the Kenya Coffee Board and then sold at auction. The public auction system dates back to before 1934. The auction method uses an agent system. Kenya has 50 licensed agents who send sample beans to their respective clients for cupping. Clients can have agents bid on coffees they like at auctions. However, this system seemed to encourage middle agents while eroding farmers' income, so in 2006 Kenya opened up 32 independent sales agents to directly contact foreign coffee buyers without going through auctions.

However, all must meet the Kenya Coffee Board's standards for quality, storage, and bank guarantees. Both systems operate in parallel. After years of development, it has become the most transparent auction distribution system, where better quality coffee can achieve better prices through cupping, encouraging more cooperatives and farms to join. FrontStreet Coffee also closely follows the coffee auction market, as this not only helps understand local coffee market changes but also ensures that the improved 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) - 85% of coffee beans are traded through the auction system

Since the establishment of the auction system in the 1930s, the vast majority of Kenyan coffee has been traded this way. Coffee auctions are held every Tuesday during the harvest season. It evolved from an "open outcry" auction system where each trader bids by pressing an electric trigger. Through this system, due to competition among agents, prices for high-quality, highly sought-after coffee can skyrocket.

② Direct Trade (often called "Second Window") - Only 15% of coffee beans are traded through direct trade

After 2006, the Kenyan government allowed farmers and foreign buyers (such as roasters or importers) to trade directly, enabling discussion and determination of prices different from auction prices before or during harvest. Some exporters also directly purchase coffee from relevant marketing agents or factories, using the previous week's auction prices for specific grades as reference for negotiation. Direct trade can allow farmers producing high-quality coffee to earn more income. When direct trade is not feasible, coffee returns to the exchange for auction sale.

What Kenyan Coffee Beans Does FrontStreet Coffee Offer?

After several rounds of tasting by FrontStreet Coffee, from an initial dozen different coffee beans from various regions, only two or three ultimately make it to the shelves. This doesn't mean the other coffee beans are inferior. FrontStreet Coffee's original intention is not just to sell, but during this process, FrontStreet Coffee aims to understand every coffee growing region, different coffee varieties within the same region, different processing methods for the same coffee variety, and establish corresponding databases, as well as comparisons between different coffee regions. FrontStreet Coffee hopes to enable more coffee enthusiasts to understand the world of coffee.

FrontStreet Coffee: Kenya Small Tomato Coffee Beans

Region: Kenya, Thika Region, Asali Processing Station

Altitude: 1550-1750m

Processing: Washed

Varieties: SL28 & SL34

Flavor: Tomato, Pear, Black Plum, Brown Sugar, Plum, Cherry Tomato

Roasting Recommendation

This FrontStreet Coffee Kenya Small Tomato bean is full and round. To fully express its bright, rich acidity, FrontStreet Coffee uses a light roast level.

Cupping Flavor

FrontStreet Coffee's Pour-over Recommendation

FrontStreet Coffee uses these brewing parameters: V60 dripper, water temperature 90°C, 15g coffee grounds, 1:15 coffee-to-water ratio, grind size similar to fine sugar particles (Chinese standard 20-mesh sieve 80% pass-through)

Here FrontStreet Coffee wants to mention why we determine grind size through sieving. This is actually the grinding recommendation for pour-over coffee provided by the Specialty Coffee Association (SCA) of America. FrontStreet Coffee has conducted extensive verification, finding that using different grind sizes for brewing produces significantly different results, and each coffee bean requires different grind sizes - this is the significance of sieving. If you don't have a sieve at home, FrontStreet Coffee suggests observing water flow speed - if water flows too quickly, the grind is too coarse; if too slowly, the grind is too fine.

FrontStreet Coffee uses segmented extraction, blooming with 30g of water for 30 seconds. Using a small water flow, pour in circles to 125g, then segment. When the water level drops and is about to expose the coffee bed, continue pouring to 225g and stop. When the water level drops and is about to expose the coffee bed, remove the dripper. (Timing starts from blooming) Extraction time is 2'00".

FrontStreet Coffee's Kenya Assalia Coffee Bean Flavor

Wet aroma has ripe tomato and floral notes. The entrance brings cherry tomato and black plum flavors, with bright acidity, clean and rich mouthfeel. Prominent sweetness in the middle section with juicy texture. The aftertaste carries berry aroma and brown sugar sweetness, with green tea fragrance.

FrontStreet Coffee: Kenya · Sasini Estate PB Coffee Beans

Region: Kiambu Region

Estate: Sasini Estate

Altitude: 1680 meters

Grade: PB

Varieties: SL28, SL34 & Ruiru

Processing Method: Washed Processing

Roasting Recommendation

FrontStreet Coffee uses light roast. Actually, the overall flavor profile of Kenyan coffee beans has already been mentioned earlier - they all feature bright acidity profiles. To emphasize this point, FrontStreet Coffee recommends adjusting toward a light roast direction.

Cupping Flavor

FrontStreet Coffee's Pour-over Recommendation

FrontStreet Coffee uses these brewing parameters: V60 dripper, water temperature 90°C, 15g coffee grounds, 1:15 coffee-to-water ratio, grind size BG#5I (Chinese standard 20-mesh sieve 80% pass-through)

Perhaps sharp-eyed readers will notice that FrontStreet Coffee's grinding parameters for this Kenyan coffee bean differ from the previous one. Each coffee bean requires different grind settings due to factors like variety, altitude, processing method, roasting, etc. Therefore, when FrontStreet Coffee receives a new roasted bean, we first sieve it to determine the appropriate hand-pour grind size.

FrontStreet Coffee uses segmented extraction, blooming with 30g of water for 30 seconds. Using a small water flow, pour in circles to 125g, then segment. When the water level drops and is about to expose the coffee bed, continue pouring to 225g and stop. When the water level drops and is about to expose the coffee bed, remove the dripper. (Timing starts from blooming) Extraction time is 2'00".

FrontStreet Coffee's Kenya Sasini Coffee Bean Flavor

Distinct black plum and cherry tomato, middle section reveals almond, finish shows honey. Juicy mouthfeel with bright acidity.

Differences Between FrontStreet Coffee's Kenya AA and Kenya PB

Actually, one can see that FrontStreet Coffee's two beans have obvious differences in grade classification, and the roasting parameters and brewing parameters used by FrontStreet Coffee also differ. Under these conditions, their flavor presentations also show perceptible differences.

Both share obvious black plum, cherry tomato, and honey flavors, developing slight nutty flavors as temperature drops, with juicy mouthfeel and bright acidity. However, AA's acidity is brighter than PB's, with overall more complex layers; PB emphasizes the sweetness of berries and honey, with overall cleaner and softer characteristics.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473