What do Kenya coffee bean grades like AA and PB actually mean?

Kenya coffee bean grades are assigned to green beans by size before roasting, so beans of similar size roast at similar rates. The scale runs E, PB, AA, AB, C, TT, T, and MH/ML. Kenya E, also called elephant bean coffee, holds the largest beans. PB means peaberry, a single round bean inside the cherry, found in only about 5 percent of Kenyan coffee.

Grading exists for roasting consistency: mixed sizes roast unevenly, with small beans over-roasted while large ones stay under-developed. AA and AB are the familiar screen sizes, while PB is separated because a round peaberry rolls and heats differently in the roaster. A Kenya PB peaberry from the Ichamama factory in Nyeri, cupped against a Kenya AA, shows how grade shapes flavor as much as origin does.

Kenya AA is often praised as one of the finest specialty coffees in the world, yet many coffee enthusiasts still have questions about what the letters AA, PB, and others actually mean. From the perspective of Front Street Coffee, this article systematically sorts out Kenya's green bean grading system, explains the definitions and origins of the E, PB, AA, AB, C, TT, T, and MH/ML grades, and takes an in-depth look at a Kenya PB peaberry from the Ichamama factory in the Nyeri region, covering origin information, cooperative background, roasting experiments, and cupping performance. Then, through a brewing comparison with Kenya AA, it presents the flavor differences between the two, helping readers gain a more comprehensive understanding of Kenyan coffee's grades and flavor characteristics.

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Kenya AA coffee is consistently regarded as one of the best specialty coffees in the world. For those who are less familiar with Kenyan coffee, Front Street is often asked what AA means. Besides AA, PB is another set of English letters that Front Street gets asked about frequently. So what do these letters actually stand for? We don't know if those of you reading this might be confused by these questions too, but today Front Street will share some knowledge related to Kenyan coffee.

Actually, AA and PB are both grade designations for Kenyan coffee. In addition, they also include:

Kenya E (Elephant Bean)

Kenya PB (Peaberry)

Kenya AA

Kenya AB

Kenya C

Kenya TT

Kenya T

Kenya MH/ML

As we all know, green coffee beans are graded before roasting, and Kenyan coffee is graded by green bean size. This is done for roasting consistency, because beans of similar size roast at similar rates, while beans of different sizes roast unevenly (for example, smaller beans get over-roasted while larger beans get under-roasted).

Kenya E coffee beans, also known as elephant-grade coffee beans, are made up of the largest Kenyan coffee beans. Kenya PB is also called pea coffee beans or peaberry. Normally a coffee cherry consists of two half beans, but a Kenya PB coffee cherry contains only one coffee bean, so a peaberry is a rounder coffee bean. This phenomenon occurs very rarely—only about 5% of Kenyan coffee beans are peaberries. Many people believe that peaberries have better flavor quality than other crops. Kenya AA coffee beans grow at an altitude of about 6,600 feet or above, with a screen size of 18.

Kenya AB has a screen size of 16. Kenya AB coffee beans are made up of A and B coffee beans. Grade A is sorted using a 6.8 mm screen, while Grade B is sorted using a 6.2 mm screen. These two types of beans, A and B, are mixed together to form the Kenya AB grade. Grade C Kenyan coffee beans have a screen size of around 15. Kenya TT refers to light-density coffee beans separated from Kenya AA, AB, and E coffee beans through aspiration. Kenya T refers to broken, defective, smaller-sized coffee beans. Finally, NH and ML refer to unripe coffee beans. So what is the difference in taste between Kenya AA and PB ? Front Street will explain this in the following article.

The above is the Kenyan coffee grading system that Front Street has summarized for you. So that everyone can better understand Kenya PB coffee beans, Front Street will give you a detailed introduction to a Kenya PB coffee bean that was purchased quite a while ago. The specific green bean information is as follows:

Kenya Nyeri Ichamama Pearl Peaberry

Country: Kenya

Region: Nyeri, Karima Village

Washing Station: Ichamama

Producer: Smallholder members of 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 dried on African raised beds under the sun

Kenya is located in eastern Africa, right next to coffee's birthplace, Ethiopia. Kenyan coffee producers can be broadly divided into two categories—large estates and smallholders—but regardless of whether they are large estates or smallholders, after processing, the coffee beans are sent to the official coffee board for grading and auction: the coffee board sends samples of the green beans about to be auctioned to interested buyers, and auctions are held every Tuesday in the capital, Nairobi (known as the NCE auction).

This Kenya peaberry from Front Street was purchased from the Othaya Farmers' Cooperative Society, located in the small town of Othaya in the Nyeri region of Kenya's central highlands, about 120 kilometers north of the capital, Nairobi. It is currently Kenya's largest coffee farmer organization, almost entirely organized and managed by smallholders themselves, and it has obtained Fairtrade certification. Othaya Cooperative's vision is to become Kenya's best-managed cooperative; its ultimate goal 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 under it, including Kamoini, Gatugi, Ichamama , and others. Othaya Cooperative was founded in 1956 and currently has about 14,000 members, making it a fairly large cooperative. In order to improve output and production quality, Othaya applies to the World Bank for grants to hire consultants for agronomy and harvest training; they also have their own nursery and laboratory, where they continuously develop new coffee varieties (e.g., Batian) for cultivation trials. Othaya Cooperative has its own cultivation techniques and marketing licenses, can trade directly with international markets, and is also a member of the Kenya Cooperative Coffee Exporters (KCCE), so it does not need to go through the NCE auction and can export coffee directly under the KCCE name.

Ichamama is located in Karuthi, Nyeri, with a total cultivated area of 310 hectares. 927 farmers cultivate beautiful coffee on the rich red volcanic soil, right beside the Ichamama River, whose waters provide an excellent source of fresh water. In addition to coffee, tea is also grown throughout the area. The altitude is extremely high, exceeding 1,800 meters. The cool nights cause the coffee cherries to mature slowly, which is expressed as a wonderful cup flavor. The reason Kenyan coffee is so acidic is also related to its altitude.

Front Street designed a roasting plan suited to the characteristics of this green bean. This Kenya peaberry green bean is emerald green in color, with relatively high moisture content and relatively high density. Because peaberries tumble more easily in the roaster drum, they heat more evenly than flat beans. However, the bean quality and density of this particular bean make heat penetration poor, so Front Street's roast design needed to allow enough heat to reach the core of the bean. By extending the dehydration time, the coffee is better homogenized during the roasting preparation stage, and then enters first crack with higher heat to express its rich berry-like flavors and full-bodied mouthfeel.

Front Street conducted a total of 4 roasting batches and observed the bean condition and aroma changes in each batch. The roasters at Front Street Coffee found that this bean absorbs heat very quickly, and using the usual drop temperature would cause the turning point to be too high. After first crack, because water vapor carries away a large amount of heat, the ROR would drop sharply (crash). So, based on the changes in the beans, we used 4 different roasting methods—1. FSSF-style (fast start, slow finish) roasting; 2. increasing heat at the yellow point to promote the Maillard reaction for an acidity-forward roast; 3. increasing heat at the brown point to promote caramelization for a sweeter roast; 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 is roasted with stepwise heat reduction, more silver skin remains attached, which is judged to be underdeveloped, and the aroma during roasting is mainly a green, sour aroma. The other three batches, because they used increased heat, had relatively ideal development, and the aroma during roasting included dark plum, blackcurrant, and sugarcane sweetness. So roasting profiles No. 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 concluded that this PB peaberry has a steady, mature aroma with a slight red wine-like acidity. On slurping, one can perceive dark berry flavors, malic acidity, a full and rich 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 dehydration time than usual can remove the astringency caused by uneven dehydration, making it drink more round and smooth.

Of course, the above is only Front Street's understanding of roasting methods: using a longer dehydration time than usual to remove moisture from the beans, and increasing heat at the brown point and before first crack to push the crack. Interestingly, supplementing heat before first crack can effectively prevent this bean's ROR from crashing and from over-developing. Kenya peaberry is a bean that Front Street Coffee has had relatively little experience with, and the roasting of peaberries, as well as the flavor of Kenya peaberries, is very much 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 aroma, 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 Thimani 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 pronounced acidity. So how should Kenyan coffee be brewed? Front Street's brewing recommendation:

Dripper: V60

Water Temperature: 90°C

Dose: 15 grams

Coffee-to-Water Ratio: 1:15

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

Front Street Extraction Method: Front Street Coffee uses staged extraction. Use 30 grams of water for a 30-second bloom, then pour in a small stream in circles until 125 grams for the first 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.) Total extraction time is 2'00".

Kenyan Coffee Characteristic Taste : This coffee has very pronounced dark berry flavors. On entry, it has a charming, bright sweet-and-sour sensation; as the temperature drops, it turns into grape-like acidity; at low temperatures, it has a stimulating plum-like sourness. Overall, it has high complexity, is delicate, and has a long finish.

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