What is a peaberry?

A peaberry - caracol in Spanish, Kibanzi in Swahili - is a coffee bean that has developed as a single, round seed inside the cherry rather than the usual two flat-sided seeds. It happens when one of the two ovules in a cherry fails to fertilise or develop, leaving the remaining seed to grow solo - producing a small, round, almost spherical bean with no flat face.

Peaberries make up roughly 5–10% of any given crop and occur naturally across all varieties and origins. They're separated from the main lot during grading at the dry mill.

They're sometimes marketed as premium on the basis that the round shape tumbles more evenly in the drum. Whether this reliably produces a better cup is debated - the evidence is mixed. Cup quality is primarily a function of origin, varietal, and processing rather than whether a bean is round or flat. Kenyan and Tanzanian peaberry lots are the most commonly available, and when they're from a quality-focused washing station, they're worth trying. Just don't pay a premium purely for the shape.