Anatomy of a Coffee Bean

Layers of Coffee Fruit and Bean Provide Unique Flavor Qualities

A green (unroasted) coffee bean is the seed at the center of the coffee fruit (coffee cherry).

The Layers of a Coffee Fruit

Starting on the outside, a coffee fruit includes the outer skin (known as the exocarp or pericarp), the pulp (or mesocarp), the pectin layer, the parchment (also called the hull or endocarp), the silverskin (also called testa or epidermis) and finally the coffee bean (endosperm).

Endosperm Dominates Coffee Bean Anatomy

Most of the coffee bean itself is comprised of endosperm, which is the tissue that is created near the time of fertilization in most flowering plants. The endosperm surrounds the embryo and supplies nutrition (starch) but may also contain proteins and oils.

In a coffee bean the endosperm caffeine content ranges from about .8 percent to 2.5%, leading to its popularity as a brewed beverage and thus a major cash crop cultivated around the world.

The Pulp and the Silverskin

Beneath the outer skin of the coffee cherry is the fruity pulp, and beneath the pulp is the silverskin. The silverskin is a very thin and fine layer of skin which envelops and adheres tightly to the seed of the fruit which is the coffee bean.

Coffee Bean Processing - Dry and Wet Processing

Dry processing coffee beans involves laying the coffee fruit out in the sun to dry for about two or three weeks while repeatedly turning the beans so they dry evenly. After drying the dried pulp is separated from the coffee beans.

Wet processing involves separating the outer flesh of the coffee fruit from the seed (coffee bean) and soaking the beans in water for one to two days (fermenting) to remove any fruit pulp or residue from the coffee beans. After this the beans are rinsed and dried in the sun or in a drying machine (forced-air drying).

Both methods of coffee processing have their pros and cons, and different effects on the brewed coffee's tastes and aromas. There are variations on these methods including pulped natural processing and semi-washed processing.

Once the beans have been processed they are known as green coffee beans (unroasted coffee beans) and have a moisture content typically around 10.5%.

Anatomy of a Coffee Bean continued:

Peaberry Coffee Beans - One Bean Instead of Two

Approximately one percent to seven percent of every coffee crop are peaberry coffee beans which are comprised of one whole coffee bean rather than the typical two half-beans.

Peaberry coffee beans are esteemed for their robust taste which is thought to be due to their higher density than regular beans.

When a cup of coffee is brewed from peaberry coffee beans it is generally believed to provide a richer aroma and smoother consistency of taste than regular coffee beans.

Coffee Plant Varietals Affect Quality of the Bean

Different varietals (cultivars) - Arabica, Canephora, and Liberica) produce coffee beans with distinct characteristics and different amounts of caffeine.

To learn more about coffee beans see our sections on harvesting and processing as well as coffee grading and roasting.

Discover the subtle tastes of coffee by learning about body, acidity, bitterness, sweetness, and the fine finish.

Thank You for reading The Anatomy of a Coffee Bean and visiting Espresso Coffee Guide.