How Does Kenya's Coffee Grading System Work?

Kenyan coffee is graded by green bean size, which helps roasters keep heat consistent across a batch. The scale runs from E-grade Elephant Beans, the largest, through AA, AB, C, TT, and T, down to MH and ML. PB means Peaberry, a single-seed fruit that forms in only about 5 percent of Kenyan coffee.

A normal coffee fruit holds two semicircular seeds, but a peaberry grows just one, so the bean is closer to spherical. Mixed sizes roast unevenly, since small beans over-roast while large ones may stay underdeveloped, which is why size grading matters. Peaberry lots such as Nyeri Ichamama Pearl cup softer and mellower than Kenya AA.

Kenya AA is often regarded as the representative of African specialty coffee, but besides AA, the letters PB also frequently appear on Kenyan coffee labels. PB stands for Peaberry, a rare form in which the coffee fruit contains only a single seed, accounting for about 5% of Kenyan coffee. This article will systematically outline the grading standards for Kenyan coffee, from E-grade Elephant Beans to AA, AB, C, TT, T, and even MH/ML, explaining the basis for each classification and the differences in specifications; at the same time, using a Nyeri Ichamama Pearl Peaberry purchased by Front Street Coffee as an example, it will provide an in-depth introduction to its origin background, processing method, and roasting approach, and through a cupping comparison with Kenya AA, present the soft, mellow flavor characteristics of peaberry and brewing suggestions.

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Kenya AA is widely recognized as one of the finest specialty coffees in the world. Many friends who are just getting into Kenyan coffee often ask Front Street what AA actually means. Besides AA, PB is also a set of letters that Front Street is frequently asked about. So what do these labels each mean? If you are also confused about this, today Front Street will talk with everyone about knowledge related to Kenyan coffee.

In fact, AA and PB are both grade names for Kenyan coffee. In addition, there are:

Kenya E (Elephant Bean)

Kenya PB (Peaberry)

Kenya AA

Kenya AB

Kenya C

Kenya TT

Kenya T

Kenya MH/ML

As everyone knows, green coffee beans must be graded before roasting. Kenyan coffee uses green bean size as the basis for grading. The purpose of doing this is to ensure roasting consistency—beans of similar size heat at similar rates, while a mixture of sizes leads to uneven roasting (for example, smaller beans are easily over-roasted, while larger beans may be under-roasted).

Kenyan E-grade coffee beans are also called Elephant grade and are the largest type of bean in Kenyan coffee. Kenya PB is also called pea bean or round bean. Normally, a coffee fruit contains two semicircular seeds, but the fruit of Kenya PB grows only one seed, so its shape is closer to spherical. The probability of this single-seed phenomenon occurring is very low, accounting for only about 5% of Kenyan coffee beans. Some people believe that peaberry has a better flavor than other lots. Kenya AA is grown at an altitude of about 6,600 feet or more, with a screen size specification of 18 mesh.

The specification for Kenya AB is 16 mesh, and it is made by mixing A-grade and B-grade coffee beans. A-grade is screened using a 6.8 mm screen, and B-grade is screened using a 6.2 mm screen. After mixing the two, it becomes Kenya AB grade. The specification for Kenya C grade is about 15 mesh. Kenya TT refers to low-density beans separated from Kenya AA, AB, and E by airflow suction. Kenya T refers to broken, defective, and relatively small beans. The final NH and ML refer to immature beans. So what is the difference in taste between Kenya AA and PB ? Front Street will introduce this to everyone below.

The above is the Kenyan coffee grading system compiled by Front Street for everyone. In order to help everyone better understand Kenyan PB coffee beans, Front Street will take a Kenyan PB coffee bean purchased a long time ago as an example and provide a detailed introduction. The specific green bean information is as follows:

Kenya Nyeri Ichamama Pearl Peaberry

Country Kenya

Region Nyeri, Karima Village

Washing Station Ichamama

Producer Smallholder farmers who are members of the Othaya Farmers’ Cooperative Society

Altitude 1,700 – 1,750 meters

Variety SL28 / SL34

Soil Volcanic soil

Temperature 18 - 26ºC

Harvest Season November – January

Processing Method Water selection, washed, then African raised-bed sun drying

Kenya is located in eastern Africa, adjacent to Ethiopia, the birthplace of coffee. Kenyan coffee producers can be broadly divided into two types—large estates and smallholders—but regardless of scale, after the coffee beans are processed, they must be sent to the official coffee board for grading and auction. The coffee board sends samples of the green beans to be auctioned to interested buyers and holds an auction every Tuesday in the capital, Nairobi (the NCE auction).

This Kenyan peaberry from Front Street was purchased from the Othaya Farmers’ Cooperative Society. The cooperative is located in Othaya town in the Nyeri region of Kenya’s central highlands, roughly 120 kilometers north of the capital, Nairobi, and is currently the largest coffee farmers’ organization in Kenya. The cooperative is almost entirely organized and managed by smallholders themselves and has obtained Fairtrade certification. Othaya Cooperative’s goal is to become Kenya’s best-managed cooperative, and its ultimate vision is to produce the highest-quality coffee, sell it at the best price, and enable all member farmers to live the best possible lives.

Othaya Cooperative has 19 washing stations, including Kamoini, Gatugi, Ichamama , and others. The cooperative was founded in 1956 and currently has about 14,000 members, making it quite large. In order to improve yield and quality, Othaya applies to the World Bank for grants and hires consultants to carry out agronomy and harvesting training; they also have their own nursery and laboratory, continuously developing new coffee varieties (such as Batian) for planting trials. Othaya Cooperative holds its own cultivation technology and marketing licenses, can trade directly with the international market, and is also a member of the Kenya Cooperative Coffee Exporters (KCCE), so it can bypass the NCE auction and export coffee directly under the KCCE name.

Ichamama is located in Karuthi, Nyeri, with a total cultivated area of 310 hectares. There are 927 farmers growing coffee on fertile red volcanic soil. Next to the washing station is the Ichamama River, whose water provides an excellent clean water source. In addition to coffee, tea is also grown in this area. The altitude is very high, exceeding 1,800 meters. The nights are cool, and the coffee cherries ripen slowly, ultimately expressing a wonderful cup flavor. The acidity of Kenyan coffee is also related to its altitude.

Front Street designed the corresponding roasting plan based on the green bean characteristics of this bean. This Kenyan peaberry green bean is emerald green in color, with relatively high moisture content and also relatively high density. Peaberries tumble easily in the drum and heat more evenly than flat beans. However, the bean quality and density of this bean result in poor heat penetration, so the roasting plan designed by Front Street needed to allow heat to fully reach the core of the bean, extending the drying time so that the coffee could homogenize better during the roasting preparation stage, and entering first crack with relatively high heat to display its rich berry-like flavors and mellow mouthfeel.

Front Street conducted a total of 4 batches of roasting and observed the bean condition and aroma changes in each batch. The roaster at FrontStreet Coffee found that this bean absorbed heat very quickly, and using the usual drop temperature would cause the turning point to be too high, while after first crack, because water vapor carried away a large amount of heat, the ROR would drop sharply (Crash). Therefore, based on the changes in the beans, we adopted 4 different roasting methods—1. FSSF-style (fast start, slow finish) roasting; 2. increasing heat at the yellowing point to promote the Maillard reaction and accentuate acidity; 3. increasing heat at the browning point to promote caramelization and increase sweetness; 4. SSFF (slow start, fast finish) roasting with gradually increasing heat.

Comparing the roasted bean condition of the 4 batches, it can be seen that if this bean used stepwise heat reduction, more silver skin would adhere, which was judged to be underdeveloped, and the aromas appearing during roasting were mainly green, acidic aromas. The other three batches, because they used heat-increasing operations, had relatively ideal development, and the aromas during roasting included dark plum, blackcurrant, and sugarcane sweetness. Therefore, roasting profiles 2, 3, and 4 were selected for cupping to see which roasting method could better showcase the bean’s flavor characteristics.

Through cupping, Front Street believed that this PB peaberry had a calm, mature aroma with a bit of red wine-like acidic fragrance. On sipping, one could perceive dark berry flavors, malic acidity, a mellow and full mouthfeel, along with sugarcane sweetness and a slight cocoa aroma. By comparing the flavors presented by different roasting methods, we found that roasting with a longer drying time than usual could remove the astringency caused by uneven dehydration, making it taste more rounded.

Of course, the above is only Front Street’s understanding of the roasting method: using a longer dehydration time than usual to remove moisture from the beans, and increasing heat at the browning point and before first crack to push the crack. Interestingly, supplementing heat before first crack can effectively prevent this bean’s ROR from dropping sharply and prevent overdevelopment. Kenyan peaberry is a bean that FrontStreet Coffee has encountered relatively little. Regarding the roasting of peaberry, as well as the flavor of Kenyan peaberry, it is very worth exploring in depth. The overall impression of this Ichamama Pearl Peaberry is different from ordinary Kenya AA. It does not have very bright acidity or ripe tomato aromas, and its flavor is soft.

Words alone are not enough. In order to directly analyze the difference between the two, Front Street brewed a cup of Kenya AA coffee beans with the same parameters. As before, let’s first give a brief introduction to the coffee bean information:

Kenya Timani Girl AA Coffee Beans

Region: Nyeri Ndima-ini Washing Station

Altitude: 1700-1900 meters

Variety: SL28&SL34

Processing Method: K72 washed

Grade: AA

Although this coffee bean is labeled as 72-hour fermentation, it actually fermented for 80 hours. Therefore, this washed Kenyan coffee will have more obvious acidity. So how should Kenyan coffee be brewed? Front Street brewing suggestions:

Dripper: V60

Water Temperature: 90 degrees

Dose: 15 grams

Coffee-to-Water Ratio: 1:15

Grind Size: Medium-fine (77% passing rate with a No. 20 standard sieve)

Front Street extraction method: FrontStreet Coffee uses staged extraction, blooming with 30 grams of water for 30 seconds, then pouring in a small stream in circles until 125 grams for the stage, and when the water level drops and is about to expose the coffee bed, continuing to pour until 225 grams and stopping. When the water level drops and is about to expose the coffee bed, remove the dripper. (Starting timing from the beginning of blooming) The extraction time is 2'00".

Kenyan coffee characteristics and taste : This coffee will have very obvious dark berry flavors, a charming bright sweet-and-sour sensation on entry, turning into grape-like acidity as the temperature drops, and at low temperature there will be a stimulating plum-like acidity. The overall layering is relatively high, delicate, and the aftertaste is long.

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