From plant to bean: the fascinating properties of the coffee plant

THE COFFEE PLANT - ITS CHARACTERISTICS

Coffee comes from the supermarket or, better still, directly from the coffee centre. Either ground or as whole beans. Right? Does coffee grow in the ground, on a tree, as a bush? Where are the beans hidden? What substances does coffee contain? "Don't know anything about botany?" The coffee cherry is a fruit. Its seeds are the coffee beans. This article provides an overview of botany.

THE PLANT AT A GLANCE

Systematics
Family of the Rubicaceae (red creepers)

Size
up to 15m, but is cut back to two to three metres in coffee plantations.

Age
over 50 years. After three years the tree bears fruit for the first time, after 20 years the yield of the plants decreases.

Leaves
large, green, glossy, up to 15cm long.

Flower
white flowers that smell of jasmine. Flowering period of only a few days.

Cherry
Ripens up to ten months. Cherries are ready for harvesting when they are deep red. Inside each coffee cherry there is a bean consisting of two seeds.

Special feature
the tree bears blossoms and fruit at the same time.

Climate
Temperature of 15-25°C; warmth, but no direct sunlight; not much water, but regular irrigation, no continuous rain

THE VARIETIES - ARABICA, ROBUSTA AND OTHERS

There are 90 different types of coffee plant. The best known are "Arabica" and "Robusta". Robusta" is a subspecies of "Coffea canephora". Coffea excelsa" and "Coffea liberica" are also represented on the world market with small shares.

THE COMPONENTS OF THE COFFEE BEAN

There are more than 1000 different substances in the coffee bean. The exact composition of the ingredients varies depending on the variety, vintage, origin, growth conditions and roasting process. The most prominent ingredient is certainly caffeine (alkaloid). Carbohydrates, fats, water, proteins, acids, minerals and flavourings are other important substances.

Carbohydrates make up the largest proportion of the coffee bean by weight. During roasting, the compounds are transformed or disappear completely. What remains are water-insoluble polysaccharides.

Glucose, sucrose and proteins also disappear during roasting. The water content shrinks from about ten to twelve percent in green coffee to one to five percent in the roasted bean.

Fats and oils are important flavour carriers. Coffee beans contain more than 80 different lipids. The fat content of Arabica beans is higher than that of Robusta beans, which can be seen in the crema. The crema of Robusta coffee is more voluminous. The high proportion of fats and oils is also the reason for the limited shelf life of coffee.

So far, more than 800 aromatic substances have been identified in coffee. Researchers are constantly looking for new aromas, but the field of bitter substances is still largely unexplored.

Acidity is important for flavour. The proportion of four to twelve percent in green coffee decreases continuously during roasting. The most important acid in coffee is chlorogenic acid. Other acids are linoleic acid, palmitic acid, acetic acid, citric acid, malic acid and oxalic acid.

The soil of origin is relevant for the minerals in coffee. Water-soluble substances such as potassium, calcium and magnesium are contained in coffee.