Usually coffee beans [seeds] develop in pairs within the coffee fruit. However, occasionally only one of the ovaries of the flower is pollinated and therefore only a single bean develops. These independent beans are called peaberries and can be found in coffees all over the world. On average peaberries develop three to nine percent of the time, so they are fairly rare and most are not separated out. Chances are that the bag of coffee you have right now contains peaberries. If you sift through you'll be able to tell by the round shape of the bean. When two beans develop side by side they flatten each other out, but when a bean has room to grow, it develops into a much rounder (oval) bean, hence the name.
Most coffee producers don't separate out peaberries, but some do. Using a screen during processing allows producers to sort the peaberries from the regular coffee beans. When producers do the extra work of separating out the peaberries it gives us the opportunity to taste a variation of that coffee. In most cases peaberries are very similar to their regular coffee bean kin, but just as they develop a unique shape, they also develop other unique qualities. Peaberries don't follow any general rules and peaberries are not necessarily better or worse than regular beans, but they give roasters and coffee drinkers the opportunity to further explore the aroma, flavor, body and acidity of a coffee.
In some instances when peaberries are separated out, the subtle difference in the coffee can make a great coffee even better. Tanzanian coffee is one of the most renowned for it's peaberries. Perhaps it's the volcanic soil, or the elevation of Mt. Kilimanjaro, but coffee processors in Tanzania have long been separating out peaberries because of their intense fruity flavor, vibrant acidity, deep body, and sweet aroma. We're very excited to offer our limited release of Tanzanian Peaberry. We're roasting it to Full City to keep it's unique flavor and aroma, while taming some of it's acidity. We hope you enjoy it!