Peaberry

Peaberry, known in Spanish as caracolillo, is a type of coffee bean. Normally the fruit ("cherry") of the coffee plant contains two seeds ("beans") that develop with flattened facing sides, but sometimes only one of the two seeds is fertilized, and the single seed develops with nothing to flatten it. This oval (or pea-shaped) bean is known as peaberry. Typically around 5% of all coffee beans harvested have experienced this small mutation.

Normal coffee beans are less commonly called by contrast flat berry.

Peaberry coffees are particularly associated with Tanzanian Coffee, although the peaberry variety of Kona coffee has also become quite prominent.

Peaberry beans roast differently from the corresponding flat berry beans; hence, to ensure an even roast in high-grade coffee peaberry beans are often separated.

Peaberry beans are widely reputed to roast better than flat berries, being said to roast more evenly, because their rounder shape minimizes sharp edges and allows the berries to roll about the roasting chamber more easily, as well as because the alleged higher bean density may improve heat transfer in the roasting process. Peaberry coffee tastes different than coffee from normal beans from the same crop. However, some sources claim that the major difference of peaberry beans is that they have been carefully sorted, which impacts the flavor profile of the coffee.

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Wikipedia