What Do PB and AA Mean in the Kenya Coffee Grading System?

Kenya grades green coffee by bean size so that similar beans roast evenly. The scale runs E (Elephant), PB (Peaberry), AA, AB, C, TT, T, and MH/ML. PB is a round single bean that forms when a cherry grows one whole seed instead of two halves, occurring in only about 5% of Kenya's crop.

AA beans are usually grown at higher altitudes and are larger than AB. E-grade Elephant beans are the largest Kenyan type. A Nyeri Peaberry from the Ichamama factory shows how green bean data, cooperative background, roast curve design and cupping flavors differ from Kenyan AA in the cup.

Kenyan coffee is renowned worldwide for its outstanding quality, but what exactly do the letters AA and PB stand for? From the perspective of Front Street Coffee, this article systematically sorts out Kenya's coffee grading system, including the meaning and distinguishing criteria of each grade—E, PB, AA, AB, C, TT, T, and MH/ML. At the same time, Front Street uses a Peaberry from the Ichamama factory in the Nyeri region as an example, documenting in detail the complete process from green bean information and cooperative background to roast curve design and cupping flavors, and conducts a brewing comparison with Kenyan AA coffee beans, helping readers gain a deeper understanding of the actual differences in taste and flavor between PB peaberries and AA coffee beans.

Kenyan AA coffee has long been 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 exactly does AA stand for? Besides AA, the letter combination PB is also frequently asked about. What do these English letters each mean? If you have the same question, today Front Street will talk with everyone about knowledge related to Kenyan coffee.

Actually, AA and PB both belong to Kenya's coffee grade naming, and besides these there are also the following levels:

Kenya E (Elephant Bean)

Kenya PB (Peaberry)

Kenya AA

Kenya AB

Kenya C

Kenya TT

Kenya T

Kenya MH/ML

As everyone knows, before coffee beans enter the roasting stage, the green beans first undergo grading. Kenyan coffee uses green bean size as the basis for grading, with the aim of ensuring roasting consistency—beans of similar size will heat at similar rates under the same conditions, while beans with large size differences are prone to uneven roasting, such as small beans being over-roasted while large beans are not yet fully roasted.

Kenyan E-grade coffee beans, also called Elephant grade, are the largest type among Kenyan coffees. Kenyan PB is called Peaberry or round bean. Generally, a coffee cherry contains two half beans, but the PB cherry grows only one complete bean, so its shape is closer to round. The probability of this phenomenon occurring is quite low, accounting for only about 5% of Kenya's total coffee. Many people believe that peaberries have better flavor performance than other grades. Kenyan AA coffee beans are usually grown at altitudes above 6,600 feet, with a screen size of 18.

Kenyan AB has a screen size of 16 and is made from a mix of A-grade and B-grade coffee beans. Grade A is screened using a 6.8 mm screen, while Grade B uses a 6.2 mm screen. These two grades mixed together constitute Kenyan AB grade. Grade C Kenyan coffee beans have a screen size of about 15. Kenyan TT refers to low-density light beans separated by airflow from AA, AB, and E grades. Kenyan T refers to broken, defective, and relatively small beans. Finally, MH and ML refer to immature coffee beans. So, what exactly is the difference in taste between Kenyan AA and PB ? Front Street will explain it for everyone in the content below.

The above is the Kenyan coffee grading system compiled by Front Street. To let everyone understand Kenyan PB coffee beans more intuitively, Front Street will take a Kenyan PB coffee bean purchased a long time ago as an example and give a detailed introduction. The specific green bean information is as follows:

Kenya Nyeri Ichamama 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, African raised-bed sun drying

Kenya is located in eastern Africa, adjacent to Ethiopia, the birthplace of coffee. Kenyan coffee producers are roughly divided into two categories—large estates and smallholder farmers. Regardless of the type, after coffee beans are processed, they are sent to the official coffee board for grading and auction. The coffee board sends samples of green beans to be auctioned to interested buyers, and an auction is held every Tuesday in the capital Nairobi, known as the NCE auction.

Front Street's Kenyan peaberry comes from the Othaya Farmers' Cooperative Society, located in Othaya town in the Nyeri region of Kenya's central highlands, about 120 kilometers north of the capital Nairobi, and is currently the largest coffee farmer organization in Kenya. The organization is basically organized and managed by smallholders themselves and has obtained Fairtrade certification. Othaya Cooperative's goal is to become Kenya's most well-managed cooperative, with the ultimate vision of producing the highest-quality coffee, selling it at the best price, and allowing 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 established in 1956 and currently has about 14,000 members, a fairly large scale. In order to improve yield and quality, Othaya applies to the World Bank for grants to hire consultants for agronomic guidance and harvest 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 coffee cooperative export organization (Kenya Cooperative Coffee Exporters, KCCE for short), 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 this fertile red volcanic soil, and right beside it is the Ichamama River, providing high-quality fresh water for coffee cultivation. In addition to coffee, tea is also grown throughout the area. The altitude is very high, exceeding 1800 meters. The cool nights allow coffee cherries to mature slowly, ultimately presenting a wonderful cup flavor. Why Kenyan coffee is so acidic is also related to its altitude.

Front Street formulated a matching roasting plan based on the characteristics of this coffee bean. This Kenyan peaberry green bean is emerald green in color, with relatively high moisture content and relatively high density. Peaberries tumble relatively easily in the roaster drum and heat more evenly than flat beans. However, the bean quality and density of this bean lead to poor heat penetration, so the roasting plan designed by Front Street needed to allow heat to fully reach the core of the bean, homogenizing the coffee better during the roasting preparation stage by extending the dehydration time, and then entering first crack with higher heat, thereby showcasing its rich berry flavors and full body.

Front Street conducted a total of 4 roasts and observed the bean condition and aroma changes in each batch. The roaster at FrontStreet Coffee found that this bean absorbs heat very quickly, and using a conventional drop temperature would cause the turning point to be too high, while after first crack, because water vapor carries away a large amount of heat, ROR would drop sharply (Crash). So, based on the bean's performance, we tried 4 roasting methods respectively—1. FSSF style (fast start, slow finish) roasting; 2. Increasing heat at the yellowing point to promote the Maillard reaction and boost acidity; 3. Increasing heat at the browning point to promote caramelization and increase sweetness; 4. SSFF (slow start, fast finish) gradually increasing heat roasting.

Comparing the roasted bean condition of the 4 batches, it can be seen that if this bean adopts a stepwise heat-reduction method, more silver skin remains attached, judged as underdeveloped, and the aroma released during roasting is mainly a grassy acidity. The other three batches, because they used heat-increasing operations, had relatively ideal development, and during roasting one could smell dark plum, blackcurrant, and sugarcane sweetness. So we selected roasting profiles 2, 3, and 4 for cupping to see which roasting method could better showcase the bean's flavor characteristics.

Through cupping, Front Street believes that this PB peaberry has a steady, mature aroma, with a slight acidic aroma of red wine. When slurping, one can feel dark berry flavors, malic acidity, a full and rich body, and sugarcane sweetness with a slight cocoa aroma. By comparing the flavors presented by different roasting methods, we found that using a longer dehydration time than usual can remove the astringency caused by uneven dehydration, making it taste rounder.

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, by supplementing heat before first crack, it can effectively prevent this bean's ROR from dropping steeply and from overdevelopment. Kenyan peaberry is a bean that FrontStreet Coffee has had relatively little contact with. Regarding the roasting of peaberries and the flavor of Kenyan peaberries, it is very worth exploring in depth. This Ichamama Peaberry gives an overall impression different from ordinary Kenyan AA; it does not have very bright acidity and ripe tomato aroma, and its flavor is soft.

Talk is cheap. In order to directly analyze the difference between the two, Front Street brewed a cup of Kenyan 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 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, using 30 grams of water for a 30-second bloom, then pouring in a small stream in circles until 125 grams for the stage break, and when the water level is about to expose the coffee bed, continuing to pour until 225 grams and stopping; when the water level is about to expose the coffee bed, remove the dripper. (Timing starts at the beginning of the bloom.) The extraction time is 2'00".

Kenyan coffee characteristics and taste : This coffee will have very obvious dark berry flavors, with a charming, bright sweet-and-sour sensation on entry; as the temperature drops, it becomes grape-like acidity, and at low temperature there will be a stimulating plum-like acidity. Overall, it has high layering, is delicate, and has a long finish.

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