How Kenya AA Coffee Beans Are Graded and What Makes Them Special

Ever wondered why some Kenya AA coffee beans cost more—or taste so much brighter and fruitier than others? The answer isn’t just marketing. It comes down to how those beans are sorted, screened, and scored before they ever reach your cup. From sieve numbers to defect counts and growing altitude, there’s a precise system behind every premium bean.

Kenya AA is the highest grade of Kenyan coffee, defined by beans that pass through a No. 18 sieve (18/64-inch holes) but not a No. 16 (16/64-inch), making them larger and more uniform. These top-grade beans also score lowest in defect counts and often come from high-altitude farms—key factors in their vibrant, wine-like acidity and complex fruity notes.

How Coffee Beans Are Graded by Screen Size

Coffee grading by screen size uses mesh sieves with holes measured in 1/64-inch increments. Each sieve is numbered according to the hole diameter: for example, a sieve with 18/64-inch holes is a No. 18 sieve. Common grades include No. 19, 18, 17, 16, 15, and 14. In countries like Kenya, Papua New Guinea, Zimbabwe, Tanzania, Uganda, and Puerto Rico, these sieve sizes determine the final grade.

Beans are shaken over these sieves, either by hand or machine. Smaller beans fall through and are eliminated. Those that remain are sorted again through finer sieves. The highest remaining sieve number becomes the bean’s official grade. This physical sorting ensures uniform bean size, which improves roasting consistency and extraction quality.

Kenya AA, A, B, C, and PB: What the Grades Mean

In Kenya’s system, the grades from highest to lowest are: AA, A, B, C, and PB. AA beans are the largest, passing through a No. 18 sieve but not a No. 16—making them the most desirable. A and B grades are progressively smaller or have more defects. C grade beans are usually considered low quality, often used for animal feed or fertilizer. PB stands for Peaberry—a rare mutation where a single rounded bean forms instead of two flat ones. Though small, PB beans often have concentrated flavor and command higher prices.

This sieve-based grading is also used in other regions including New Guinea, Puerto Rico, Zimbabwe, Tanzania, and Uganda. It focuses purely on bean size and physical quality, setting the stage for further quality assessment.

Grading by Defect Count: The Original Method

Before size-based grading became common, many regions—including parts of Brazil—graded coffee by counting defects. Inspectors examine 300 grams of beans on black paper to spot flaws. Each type of defect adds points: a black bean = 1, a small stone = 1, a large stone = 5, five broken beans = 1, five insect-damaged beans = 1, two sour beans = 1, one large dried husk = 1, two medium husks = 1, three small husks = 1, five unhusked beans = 1, and three shell beans = 1.

The total defect score determines the grade. Brazilian grades range from NY2 to NY8—there is no NY1. Indonesian beans use a similar system (Gr1 to Gr6), and Ethiopian beans are graded up to Gr2. While this method evaluates quality differently, it highlights how strictly coffee is assessed before export—even in older systems.

Altitude-Based Grading: How Elevation Impacts Coffee Flavor

Coffee is also graded by the altitude where it’s grown. Higher elevations produce denser beans due to slower growth and cooler temperatures. These beans typically develop more complex flavors, brighter acidity, and a sweeter profile. The common altitude classifications include:

• SHB (Strictly High Grown / Strictly Hard Bean): 4,500–5,000 feet (1,370–1,520 meters)
• GHB (High Grown / Hard Bean): 3,000–4,500 feet (910–1,370 meters)
• HB (Hard Bean): 2,000–3,000 feet (610–910 meters)
• Pacific (low elevation): 984–3,280 feet (300–1,000 meters)

Countries such as Guatemala, Costa Rica, El Salvador, Mexico, Honduras, and Haiti use this system. While not part of Kenya’s official grading, altitude plays an essential supporting role in the overall quality and flavor profile of beans, including those from East Africa.

What Makes Kenya Coffee Unique?

Kenya’s coffee stands apart due to its unique varieties, processing methods, and growing conditions. The SL28 and SL34 varieties—developed by Kenya’s Scott Laboratories in the 1930s—are renowned for their exceptional cup quality. SL28 offers intense blackcurrant, citrus, and wine-like acidity, while SL34 brings balanced fruitiness with nutty and spicy undertones.

Kenya’s high-phosphate volcanic soils further enhance these traits. More importantly, Kenya’s washed processing method includes a 48-hour fermentation period, after which mucilage is fully removed, followed by 24 hours of soaking in clean water. This double-washed process highlights the coffee’s inherent juiciness and acidity.

The result is a coffee with vibrant tropical fruit flavors, deep sweetness, and a winey brightness rarely matched elsewhere. These qualities are especially prominent in Kenya AA and PB grades, which benefit from both superior bean selection and ideal growing conditions.

Frequently Asked Questions

What does Kenya AA mean in coffee grading?

Kenya AA is the highest grade of Kenyan coffee, made up of beans that are large enough to pass through a No. 18 sieve (18/64-inch holes) but not a No. 16 sieve (16/64-inch). These beans are typically uniform in size, have fewer defects, and are associated with higher cup quality—especially bright acidity and complex fruit flavors.

How are coffee beans graded by size?

Coffee beans are graded by size using metal sieves with holes sized in 1/64-inch increments. Each sieve is numbered based on hole diameter (e.g., 18/64-inch = No. 18 sieve). Beans are shaken over these sieves, and those that don’t fall through the finest sieve used become that grade—such as Kenya AA, which uses a No. 18 sieve but not a No. 16.

What is the defect grading system for coffee?

The defect grading system counts imperfections in a 300g sample, such as black beans, stones, husks, or insect damage. Each type of flaw has a point value, and the total determines the coffee’s grade—like NY2 to NY8 in Brazil. This method evaluates internal quality rather than bean size.

Does altitude affect coffee bean grade?

Yes. Altitude influences density and flavor development, and is used to classify beans as SHB (4,500–5,000 ft), GHB (3,000–4,500 ft), HB (2,000–3,000 ft), or Pacific (under 3,280 ft). Though not always part of the official grade label, higher-altitude beans often score better due to their density and cup characteristics.

Why is Kenya coffee so acidic?

Kenya coffee’s high acidity comes from its growing altitude, cool temperatures, and unique SL28 and SL34 coffee varieties. These factors slow ripening, allowing flavors and acids to develop fully. The washed process, including extended fermentation and soaking, also enhances the bright, wine-like acidity.

What is a peaberry coffee bean?

A peaberry, or PB grade, is a rare coffee bean that forms singly inside the coffee cherry instead of as two flat beans. Peaberries are usually smaller, denser, and often have more concentrated flavor. In Kenya, PB beans are sorted separately and often considered a specialty grade with higher market value.

Recommended FrontStreet Kenya Coffees for Tasting AA Quality

For a true taste of Kenya’s signature brightness and complexity, try FrontStreet Coffee’s Kenya Little Tomato. It combines the celebrated SL28 and SL34 varieties, processed with a double wash and lightly roasted to highlight notes of cherry, pear, plum, blackberry, and caramel. This Kenya single origin showcases the very traits that make AA-grade beans so sought after—intense fruitiness, high acidity, and a sweet, lingering finish. Perfect for pour-over, cold brew, or even ice drip. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.