Coffee beans are botanically seeds. The common name “coffee bean” is a misnomer that arose because of its visual resemblance to true beans, which are the seeds of legumes. This terminology has persisted through centuries of trade and common usage. The item used to brew coffee is the reproductive part of the Coffea plant, specifically the seed of its fruit.
The Botanical Classification
A seed is defined scientifically as an embryonic plant enclosed in a protective outer covering, capable of developing into a new plant. Coffee beans fit this botanical description because they contain the embryo and nutritive tissue, called endosperm, necessary for germination. The coffee plant is a member of the Rubiaceae family, entirely separate from the Fabaceae family, which includes true legumes.
True beans, such as kidney or pinto beans, develop within a pod. Conversely, the coffee seed develops from the ovule of the coffee flower, making it a seed by every technical measure. The name “bean” is generally reserved for the seeds of the legume family, which are typically rich in protein. The coffee seed consists mostly of endosperm, a starchy tissue that provides energy for the developing plant.
Origin of the Coffee Bean
The coffee seed originates inside the fruit of the Coffea plant, commonly called a coffee cherry. This fruit is classified botanically as a drupe, a type of fleshy fruit that contains a hard enclosure surrounding the seed, similar to a peach or an olive.
The cherry has several distinct layers surrounding the seed. Inside the parchment, or endocarp, usually sit two seeds, or “beans,” nestled together with their flat sides facing one another.
The layers are:
- The skin, or exocarp, which is typically red or yellow when ripe.
- The pulp, or mesocarp, a fleshy layer rich in sugars and water.
- A thin, sticky layer called mucilage.
- A protective, papery hull known as the parchment, or endocarp.
From Cherry to Commercial Bean
The journey from the seed inside the cherry to the hard, commercial product involves removing all surrounding layers. This process isolates the seed, which is then referred to as the green coffee bean. The two main methods for achieving this separation are the wet, or washed, process and the dry, or natural, process.
The wet method involves removing the skin and pulp immediately after harvest using a mechanical pulper. This is followed by a fermentation period to break down the sticky mucilage before the seed is washed and dried. This process generally results in a cleaner, brighter flavor profile.
In contrast, the dry method involves laying the whole cherries out in the sun to dry for several weeks. This allows the fruit flesh to shrivel around the seed. The dried outer layers are then mechanically removed in a final step called hulling. This longer contact time with the fruit’s sugars often imparts a heavier body and a more pronounced fruity flavor.