Origin record
Kenya
Where AA means a bean size and nothing else - and where the two most famous selections may not have the lineage their story gives them.
Commonly got wrong
AA is the single most misunderstood mark in coffee retail. It means the bean passed over a screen 18 and did not pass over a screen 20. It is a size. Also worth knowing: genetic testing suggests SL28 and SL34 sit closer to Typica than to Bourbon, which contradicts the French Mission origin story attached to them.
Kenya produces one of the most recognisable cup profiles in coffee and one of the most consistently misread grading systems.
AA is a screen size
Kenya grades by screen: AA, AB, PB, C, E, TT and T. AA describes beans that passed over a screen 18 and not over a screen 20. It is a measurement of physical size, made by a machine, and it is not a statement about flavour. An AB lot from a well-run factory routinely outcups an AA from a poor one.
This is structurally the same error as Supremo in Colombia. A physical preparation term gets marketed as a quality tier, and the marketing sticks because the letters look like a ranking.
SL28 and SL34 may not be what the story says
Both selections came out of Scott Laboratories, and SL34 in particular carries an origin story about a single tree in a field labelled French Mission – which is to say, Bourbon. Genetic work has suggested both sit closer to Typica than to Bourbon, which would make the French Mission account wrong.
We record this as contested rather than resolved. What matters for a buyer is narrower and firmer: the lineage story attached to a famous selection is not itself evidence, and where genetic testing exists it outranks the story.
Qualifications on the record
- What the price actually refers to
- The Nairobi Coffee Exchange weekly auction is the main price discovery mechanism, quoted per 50 kg bag rather than per pound.
- How the grades nest
- Kenyan grades are SCREEN SIZES. AA is a bean size, not a cup score, and an AB lot from a good factory routinely outcups an AA from a poor one. This is the same error as Supremo in Colombia, in a different alphabet.
- Harvest qualification
- The fly crop is genuinely secondary here, unlike Colombia's mitaca, but it is still a real harvest with its own lots.
- Typical cup
- Blackcurrant, a dense phosphoric acidity and a heavy syrupy body in the best lots - a profile particular enough that it is often described as tasting of Kenya rather than of a variety.