What's So Special About Peaberry Coffee

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We’re thrilled to be offering the Kenya Nyeri Thageini Peaberry as one of our featured coffees at Seattle Coffee Works. We only offer one peaberry coffee each year, and we hope you’ll agree this special lot is one of the finest coffees available.

Carol and I cupped (sampled) 60 Kenya Cooperative coffees in January 2020. We tried 25 peaberries to find just the right one for Seattle Coffee Works.

What’s Special about Peaberries

Peaberries are rare. Only 5-10% of all coffee cherries grow in such a way that they produce only one coffee seed. The vast majority of coffee cherries have two seeds. (In other words, like most flowering plants, coffee is a dicot, or dicotyledon, with two embryonic leaves in its seed.)

You can’t really tell if a coffee cherry is a peaberry while it’s on the branch. If you touch it carefully, you might notice it’s a little more round than usual. Most coffee cherries are slightly oval. Through the skin, you might be able to feel that there’s just one seed, instead of two.

Peaberries really only show up in the last stage of the sorting process at the “dry mill.” This is when the already dried green coffee beans are screened and separated according to size. Peaberries are one of the sizes. (Some other sizes include AA - the largest - and AB - the second largest.)

This close-up of a regular green coffee bean (left) and a peaberry (right) shows the characteristic peaberry shape.

Initially, peaberries were considered a defect because of the oval shape appearance that is totally different from what a coffee bean looks like. As a result of a natural mutation their size and shape is different from other green coffee beans, which usually have one flat side and one round. Peaberries are rounded, like a pea.

But then, people started to realize that peaberries can exhibit special qualities, usually because all the nutrients that the coffee bean receives during its development go to a single seed instead of two.. They can taste similar but more intense than other coffee from the same plant, resulting in complex and sometimes unexpected flavors.

Peaberries are an adventure in a coffee bean.

Mythbusting the Peaberry

Now you know that peaberry coffee is a shape of coffee seed that happens occasionally. But just because it’s rare does not mean a peaberry is good. The quality of any peaberry corresponds to the quality of the coffee plant (and processing) that it came from - it lives in the same soil, gets the same care, and goes through all the same drying and sorting steps as its kindred coffee on the same plant.

This coffee seedling has a hardy SL root base with a Ruiru 11 grafted on top.

Peaberry coffee is not a variety of coffee. In fact, because peaberries are only discovered at the final stage of sorting and processing, it’s very difficult to trace them back to the exact kind of coffee plant that they came from. Most of our peaberry coffee comes from the SL28 and SL34 varieties, because those are the botanical varieties of coffee that the farmers at the Thageini Cooperative grow. Recently, some of the farmers are starting to use Ruiru and Batian varieties. (See David Ngibuini’s article for a Kenyan farmer’s perspective on these and other varieties.)

Even as coffee farmers, harvesters, and the wet and dry mill operators innovate and improve their processes, it’s likely that we’ll continue to see natural variations like the peaberry. These small aberrations from the norm can be seen as nature’s insurance policy - a way of diversifying its seeds and increasing the chances that the species can survive.

For us, we can consider the peaberry a happy, flavorful accident!