What we commonly call “coffee beans” are not botanically beans. They are the seeds found inside a small, fleshy fruit known as a coffee cherry. This coffee cherry, a drupe, is the true fruit of the coffee plant, and its seeds are what we process, roast, and brew into coffee.
The Coffee Plant and Its Fruit
The coffee plant, belonging to the Coffea genus, is a shrub or small tree that produces these fruits. A coffee cherry starts green and ripens to a vibrant red, yellow, or purple, depending on the variety. The structure of a coffee cherry consists of several distinct layers, each playing a role in protecting the valuable seeds within.
The outermost layer is the exocarp, which is the skin of the cherry. Beneath this skin lies the mesocarp, a fleshy, sweet pulp. Encasing the seeds is a parchment-like layer called the endocarp, which hardens as the fruit matures and serves as a protective barrier. Inside the endocarp, usually, are two seeds, nestled with their flat sides facing each other. Each seed is also covered by a thin layer known as the silverskin.
From Cherry to Bean
Transforming the coffee cherry into the dried “bean” involves specific processing methods that remove the fruit layers. Two methods are widely used: wet (washed) processing and dry (natural) processing. Each method influences the final flavor profile.
In dry processing, the entire coffee cherry is spread out to dry in the sun. During this period, the fruit’s sugars and flavors are absorbed by the seeds, which can result in a fruitier and sweeter profile. Once dried, the skin and dried fruit flesh are mechanically removed to extract the seeds.
Wet processing involves removing the fruit layers before drying the seeds. After harvesting, the cherries are pulped to remove the outer skin and most of the pulp. The remaining seeds, still covered in a sticky mucilage layer, are then fermented in water tanks to break down this layer. After fermentation, the seeds are washed and then dried, resulting in a cleaner, brighter, and more acidic flavor profile in the final coffee.
Why We Call Them Beans
Despite being botanically classified as seeds from a fruit, coffee seeds are colloquially called “beans.” This usage stems from their visual similarity to true legumes, such as kidney beans, due to their oval shape and a crease down the middle. This resemblance led to the adoption of “bean” as a simple, familiar descriptor.
Historical and cultural factors also contributed to this naming convention. Early traders and merchants used the term for familiarity when introducing coffee to new markets, and the name became widely accepted. While botanically inaccurate, “coffee bean” is universally understood and used in the coffee industry and by consumers alike.