Anatomy of the Coffee Fruit and Bean

Oct 30, 2019 | Let's talk about coffee

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Anatomía de la fruta y semilla del café

The coffee fruit (coffee cherry) is mainly divided into two parts, Pericarp and Seed.

In the following article, we show you the Anatomy of the Coffee Fruit and Bean.

PERICARP
The pericarp is the three outer layers of the fruit: the exocarp (skin), the mesocarp (mucilage) and the endocarp (parchment).

SEED
The coffee seed or bean comprises a silver skin, endosperm, and an embryo. Coffee seed sizes vary depending on the variety; however, on average they are 10 mm long and 6 mm wide.

Parts of coffee cherry

(A) Longitudinal and (B) Cross section of the coffee fruit. (a) Exocarp, (b) Mesocarp, (c) Endocarp, (d) Perisperm, (e) Endosperm, (f) Embryo.

Exocarp (Skin)

The exocarp, also known as peel, skin or epicarp, is the outermost layer of the coffee fruit. It is formed by a layer of parenchymal cells.

It’s color changes depending on the maturity of the fruit. At the beginning of the development of the fruit, it is green due to the presence of chloroplasts.

The color after ripening, depending on the coffee variety, is red or yellow. The red color comes from anthocyanin pigments, while the yellow color is attributed to luteolin.

Exocarp, skin of coffee fruit (cherry) with different colors

Mesocarp (Mucilage, pulp)

Also known as mucilage, it is the pulp of the coffee fruit.

In the green coffee fruit, the mesocarp is rigid, as the fruit matures the pectolytic enzymes break the pectic chains, resulting in an insoluble hydrogel very rich in sugars and pectins.

In the wet processing method, the mucilage is removed by controlled fermentation. In the honey processing method, the mucilage is left adhering to the bean during drying. And in the dry processing method, the mucilage, along with the exocarp, is left intact during drying.

Studies have shown that the mucilage/water ratio of the mesocarp increases as the altitude increases.

Mesocarp, mucilage or coffee pulp

Endocarp (Parchment)

It is the innermost layer of the pericarp and is the layer that covers and protects the bean, has a pale yellow color and is of a hard and fragile consistency when it has dried. It is formed from 3 to 7 layers of sclerenchyme cells.

The coffee bean is coated with this protective layer is often called parchment coffee and in some countries, it is the way coffee is marketed.

The parchment layer should be removed before roasting the coffee.

Endocarp or parchment

Perisperm (silver skin)

The perisperm it’s also known as silver film, which is the outermost layer that surrounds the seed. Some remains of the silver skin remain adhered to the bean and detach themselves totally or partially during the roasted coffee process.

Endosperm (Seed)

Each coffee cherry contains inside, two seeds called Endosperms that usually have a hard consistency and greenish or yellowish color. It may be the case where a single seed (Peaberry) or three seeds are developed.

The chemical content of the endosperm is very important since it is the precursor of the flavor and aroma of roasted coffee.

The chemical compounds found in the endosperm can be classified as soluble or insoluble in water. The water-soluble compounds are caffeine, trigonelline, nicotinic acid (niacin), at least 18 chlorogenic acids, mono-, di- and oligosaccharides, some proteins and minerals, and carboxylic acids.

Water-insoluble components include cellulose, polysaccharides, lignin, and hemicellulose, as well as some proteins, minerals, and lipids.

The coffee endosperm is usually called green coffee and is the way it is usually marketed. Green coffee is the one that goes through the roasting process where all its flavors develop.

Endosperm, coffee seeds. Also known as Green Coffee

Embryo

It is located on the convex face of the endosperm. The embryo is composed of a hypocotyl (embryonic axis) and two cotyledons and has a length of 3-4 mm. Coffee seeds germinate through epigeal germination, in which the hypocotyl lengthens and pushes the seed up above the ground. The original cotyledons remain underground; however, new cotyledons will be formed.