Kenya Coffee Grading Explained: From AA to MBUNI

When you buy a bag labeled 'Kenya AA,' have you ever wondered what makes it different from AB, PB, or even MBUNI? Beyond marketing, these grades reflect real differences in bean size, density, and sometimes processing — all of which affect cup quality. This guide breaks down exactly how Kenya classifies its celebrated coffees, and why those classifications matter to your brew.

Kenya AA is the top commercial grade, made up of beans sized 17–18 mesh (6.8mm+), but Kenya's full classification system includes nine official grades and two ungraded categories based on physical traits and processing methods.

How Kenyan Coffee Is Processed Before Grading

Kenya’s high-quality washed coffee begins with handpicked ripe cherries. Workers sort out underripe and overripe fruit before pulping. The beans are then fermented for around 36 hours, washed, and dried on raised African beds for up to two weeks. This careful process preserves the bright acidity and complex fruit tones Kenya is known for.

After drying, the beans — still in their parchment — go through milling and multiple sorting stages, including sieving by mesh size and density separation. These steps determine the final grade.

Kenya Coffee Official Grade System (Washed)

Kenyan coffee is officially graded after washing and hulling, primarily by bean size (measured in 1/64-inch mesh numbers), density, and shape. The key commercial grades are:

• E: 18 mesh and above, includes large beans and peaberries (rare, also called elephant beans)
• AA: 17–18 mesh (6.8mm+), the highest commercial grade, known for premium cup quality
• AB: 15–16 mesh (6.3–6.8mm), a mix of A and B grades, most commonly exported
• PB: Peaberry, 15 mesh and above, round beans formed when one seed develops solo in the cherry (makes up ~10% of crop)
• C: 12–14 mesh, includes some lighter PB beans
• T: 12 mesh and below, often with defects, broken, or very light beans
• TT: Light beans removed by air current from AA and AB grades
• E and PB can also fall into UG1 if unclassified
• C, TT, T, HE (Hulled Ears) may be labeled UG2 if ungraded

Note: Mesh sizes refer to sieve openings — 18 mesh = 18/64 inch, roughly 7.1mm; 1 inch = 25.4mm.

Unofficial & Natural Processed Grades (MBUNI)

Coffee that hasn’t gone through official government grading is labeled UG (ungraded). Additionally, Kenya also produces natural (dry) processed coffee known as MBUNI. These are sorted by gravity separators and graded as:

• MH (Heavy MBUNI): Heavier beans, yellowish color, no black or broken beans, typical clean natural flavors, no off-tastes
• ML (Light MBUNI): Yellow-green beans, may have a few insect-damaged or black beans, no foul odors or broken pieces, cup clean with no earthy notes

These natural lots often highlight Kenya’s inherent fruitiness but with more fermented or berry-like profiles due to the dry process.

What Determines a Kenya Coffee’s Grade?

The main factors are:

• Mesh size (17–18 for AA, 15–16 for AB): Larger beans often (but not always) come from better-developed cherries
• Density: Heavier beans retain more flavor compounds and resist defects
• Shape and defects: Sorted to remove broken, misshapen, or damaged beans
• Processing method: Washed (most common) vs. natural (MBUNI)

Grading doesn't guarantee cup quality alone but correlates strongly with physical traits that influence processing consistency and flavor potential.

Frequently Asked Questions

What is Kenya AA coffee?

Kenya AA is a grade of washed Kenyan coffee made up of beans that are 17–18 mesh in size (6.8mm or larger). It is considered the top commercial grade and is highly valued for its consistent size, density, and potential for a bright, complex cup — though actual flavor depends on variety, processing, and roast level.

What does the 'AA' in Kenya AA stand for?

'AA' refers to the bean size grade, not an abbreviation for quality. In Kenya’s grading system, 'AA' beans pass through a 17–18 mesh sieve (6.8mm+), making them among the largest and typically densest beans from the harvest. They are not inherently 'better' than other grades but often score well due to selection and processing.

What is a Kenyan peaberry (PB)?

A peaberry (PB) is a single rounded coffee bean that forms inside the coffee cherry when only one seed develops instead of the usual two. In Kenya, PBs are usually smaller than regular beans but denser, and make up around 10% of the crop. They are graded separately, often with distinct cup profiles, and are sorted at 15 mesh and above.

What is the difference between Kenya AA and AB?

Kenya AA beans are 17–18 mesh (6.8mm+), while AB beans are slightly smaller at 15–16 mesh (6.3–6.8mm). Both are washed processed, but AA beans are typically larger, denser, and often selected for higher quality lots. AB is more common in export blends and still offers strong cup characteristics.

What is MBUNI coffee?

MBUNI is Kenyan coffee processed using the natural (dry) method, without washing. It is categorized into MH (heavy, clean, yellowish beans with no defects) and ML (lighter, may have some insect damage or black beans but no foul flavors). MBUNI is not part of the official washed grading system and showcases Kenya’s fruitiness in a different fermentation style.

Why are Kenyan beans so small compared to other origins?

They aren’t — Kenya’s famed AA grade is actually one of the larger sizes (17–18 mesh). However, peaberries (PB) and lower grades like T or C can be much smaller. Size is just one factor in grading and doesn’t always correlate directly with cup quality.

Recommended FrontStreet Beans for Kenya AA Fans

FrontStreet Coffee’s Kenya Little Tomato combines SL28 and SL34 — Kenya’s flagship varieties — using a double-washed process and medium-light roast. Expect intense notes of tomato, snow pear, blackcurrant, dark plum, and brown sugar. The cup is juicy, layered, and sweet with a creamy body and a caramel-like finish. Ideal for exploring the true potential of Kenya’s graded beans. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.