What we refer to as a “bean” is actually the seed found inside a small fruit. The small, reddish oval that grows on trees of the Coffea genus is the birthplace of the world’s most popular beverage. This misunderstanding stems from the fact that the fruit’s flesh is entirely removed before the seed is prepared for roasting and brewing.
The Direct Answer: Botanical Classification
The coffee fruit is technically a berry, though botanists classify it more specifically as a drupe. A drupe is a fleshy fruit characterized by a hard, outer layer, or shell, which encloses the seed, such as a peach or an olive.
The familiar term “coffee cherry” is widely used within the industry because the fruit’s appearance closely resembles a culinary cherry when it ripens to a deep red or, sometimes, yellow color. This common name helps distinguish it from other fruits, but the botanical classification as a drupe is more precise than simply calling it a berry. The genus for all coffee plants is Coffea, which belongs to the family Rubiaceae. The two most economically significant species are Coffea arabica and Coffea canephora, which produce the seeds we consume.
Anatomy of the Coffee Fruit
The outermost layer is the skin, or exocarp, which is thin and waxy. This skin acts as the first barrier, transitioning from green to a vibrant red or yellow as the fruit matures over a period of six to eleven months. Beneath the skin is the fruit’s fleshy pulp, known as the mesocarp, which is rich in sugars and water.
A sticky, gelatinous layer called the mucilage is part of the mesocarp and contains natural pectin and sugars. This layer is influential in developing the final flavor profile of the coffee during processing. Encasing the seed is a protective shell called the parchment layer, or endocarp, which hardens as the fruit ripens.
Inside the parchment, the seed is covered by a thin membrane called the silverskin, or epidermis. Finally, the seed itself, the green coffee bean, is the endosperm of the fruit, where essential compounds like caffeine are stored. Most coffee cherries contain two seeds nestled together, though a natural mutation sometimes yields a single, rounded seed called a peaberry.
From Fruit to Bean: Processing Steps
The processing method chosen dictates how the fruit layers are stripped away and has a significant impact on the final flavor profile of the roasted coffee. The two primary methods are wet (washed) and dry (natural) processing.
Dry Processing
In the dry, or natural, method, the entire fruit is left intact after harvest and spread out on patios or raised beds to dry in the sun for two to three weeks. The fruit’s skin and pulp dry onto the parchment, which allows the seed to absorb the fruity, sugary characteristics of the surrounding layers. After drying, the brittle, dried outer layers—collectively called the husk or pericarp—are mechanically removed in a single hulling step to isolate the green bean.
Wet Processing
The wet, or washed, method is more complex, beginning with the immediate removal of the skin and much of the pulp using a mechanical pulper. This process leaves the seed covered only by the sticky mucilage and its parchment layer. The seeds are then fermented in water tanks for a period, allowing enzymes and microbes to break down the sticky mucilage. Finally, the seeds are washed clean and dried, still encased in the papery parchment, before the parchment and silverskin are removed during the final milling stage.