How Kenya Classifies Its Specialty Coffee Grades

When you buy a bag labeled "Kenya AA," have you ever wondered how that grade was decided? Unlike generic origin labels, Kenya employs a detailed, multi-tiered classification system based on physical traits and processing quality — one that directly impacts cup profile and market value. For specialty buyers, understanding these grades reveals what to expect in the cup and why certain lots command premium prices.

Kenya’s top specialty grades are AA (17–18 mesh), AB (15–16 mesh), and PB (peaberry, 15+ mesh), with E (18+ mesh including round beans) considered the largest and often most prized. Lower grades like T, C, and HE indicate smaller, denser, or defective beans. Beyond graded lots, ungraded (UG) and natural (Mbuni) coffees follow separate, less uniform standards.

How Kenya Grades Washed Coffee by Size and Shape

Most Kenyan specialty coffee begins with handpicked cherry, which is sorted to remove underripe (unripe) and overripe (overripe) fruit. After depulping, the beans ferment for around 36 hours, then dry on raised African beds for several days. Once milled (parchment removed), the green beans are evaluated primarily by screen size, shape, and density.

The main graded categories are:

• E: 18 mesh and above (including round beans), often called "elephant beans"; includes some peaberry. Rare and large.
• AA: 17–18 mesh. The top commercial and specialty grade; typically larger, denser beans with high cup potential.
• AB: 15–16 mesh. A blend of the A and B sieves; makes up a large portion of exportable Kenyan coffee.
• PB: Peaberry, 15 mesh and above. These are single round beans formed when one seed in the coffee cherry fails to split. They account for roughly 10% of Kenyan lots and are often prized for concentrated flavor.

Additionally:

• TT: Lighter beans removed from AA and AB via air classification. Smaller or less dense.
• C: 12–14 mesh, plus light beans from PB. Lower-grade washed.
• T: Below 12 mesh, often with defects, broken, or very light beans.
• HE: Any beans not fitting other grades; often flawed or irregular.

These grades are assigned after the beans pass through a series of screens (mesh sorters) and density separators. Larger, denser beans — especially E and AA — typically have more even roast profiles and higher solubility, contributing to the complex acidity and clarity Kenyan coffees are known for.

Ungraded and Defective Lots: UG and UG2

Not all Kenyan coffee makes the cut for the top grades. Beans that haven’t been officially sorted by size or that contain a higher percentage of defects fall into ungraded (UG) categories.

• UG1: Includes E, AA, AB, and PB that didn’t meet strict export or auction standards, often due to minor defects or size inconsistencies.
• UG2: Includes C, TT, T, and HE. These beans are more likely to contain broken, chipped, or defective beans and are usually sold at a discount.

While UG lots aren’t typically sought after by specialty roasters, some are still processed well and can yield surprisingly balanced cups — though with more variability in cup quality.

Mbuni: Kenya’s Natural (Sun-Dried) Processed Coffee

Beyond washed (wet-processed) coffees, Kenya also produces natural-processed beans known locally as Mbuni. These are not washed or fermented in the same way, but are instead dried with the cherry intact. Mbuni beans are separated by gravity tables into two main quality tiers:

• MH (Heavy Mbuni): Heavier beans, yellowish in color, free from black beans, broken pieces, or dried fruit. These lots show typical natural process flavors — think berry, funk, and fermentation — without off or dirty tastes.
• ML (Light Mbuni): Lighter, yellow-green beans that may include a small number of insect-damaged or black beans, but no foul-smelling or moldy defects. These still avoid strong earthy or sour off-flavors.

Natural Mbuni coffees are less common in the specialty export market, but they represent an important segment of Kenya’s domestic and regional trade. When well sorted, they can offer heavy body and exotic fruit tones.

Why Size and Density Matter in Cup Quality

Kenya’s grading system emphasizes physical traits like bean size (measured in 6.8mm for 18 mesh down to 6mm for 12 mesh), because larger, denser beans typically roast more evenly and extract more consistently. That’s why AA and E grades — the largest — are often associated with brighter acidity, clearer sweetness, and more complex fruit notes.

Density also affects how beans absorb heat during roasting. Heavier beans (like those in AA and MH categories) usually develop more structured sweetness and a fuller mouthfeel. Smaller or lighter beans (like T, C, or ML) can still produce decent cups but are more prone to inconsistency, especially when processed or roasted less carefully.

Image of a typical gravity table sorting Mbuni beans:

Frequently Asked Questions

What is the highest grade of Kenyan coffee?

The highest commercial and specialty grade is Kenya AA, which includes beans that are 17–18 mesh in size. These beans are typically larger, denser, and considered to have the best cup potential, often exhibiting bright acidity and complex fruit flavors.

What does PB mean in Kenyan coffee?

PB stands for peaberry, a natural mutation where a single rounded bean forms instead of two flat beans. In Kenya, PB beans are usually 15 mesh and above and make up around 10% of harvests. They are often separated and sold as a distinct grade due to their concentrated flavor profile.

What is the difference between Kenya AA and AB?

Kenya AA beans are 17–18 mesh in size and generally larger and denser, often considered higher quality. AB beans are 15–16 mesh, a mix from the A and B sieves, and make up a significant portion of export lots. Both can produce excellent cups, but AA is typically brighter and more uniform.

What are UG and UG2 grades in Kenyan coffee?

UG (Ungraded) includes beans from top grades (like E, AA, AB, PB) that did not meet strict size or defect criteria. UG2 includes lower grades such as C, TT, T, and HE — smaller, often defective beans that are sold at a discount and are more likely to produce inconsistent cups.

What is Mbuni coffee in Kenya?

Mbuni refers to Kenyan coffee processed naturally (dry-processed) with the cherry left on the bean during drying. It is separated into MH (Heavy Mbuni), which is yellowish and free of major defects, and ML (Light Mbuni), which may have some flaws but avoids strong off-flavors. Mbuni is less common in specialty export markets.

Does bean size really affect coffee flavor?

Yes. In Kenya’s grading system, larger and denser beans (like AA and E) often roast more evenly and extract more consistently, leading to brighter acidity, clearer sweetness, and more defined fruit flavors. Smaller beans may still produce good cups but are more prone to uneven roasting and extraction.

Recommended FrontStreet Beans for Exploring Kenya's Grades

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