Coffee is an evergreen plant that grows as a shrub or small tree. There are about 90 types of coffee plants in the world, but few have any significance for the coffee we drink every day. Biologists speak of the “Coffea” genus, from the Rubiaceae family, which has its origin in the Ethiopian province of Kaffa.
The shrubs of the coffee plant are up to 4 metres high and have oval leaves with white flowers arranged in a cluster. In each stone fruit of the plant, called coffee cherries, there are two seeds – the coffee beans we all know. Depending on the type of coffee plant, the fruits ripen 7 to 11 months after fertilisation and undergo a colour change from green to yellow to red during this time.
Of the approximately 90 different coffee plant species, C. arabica (Arabica coffee) and C. canephora (Robusta coffee), both of which originate from Africa, are the most commonly used. The varieties C. liberica and C. excelsa are used for coffee production too but seldom.
The flowers of the coffee shrub are white, with multi-flower clusters forming on the plant. After fertilisation, these are transformed into the so-called coffee cherry. This is a stone fruit, and the two seeds it contains are the coffee beans we know.
Coffee originally comes from tropical Africa and Madagascar, but is now widespread in all tropical and subtropical regions.
Creating a taste profile with blending
Arabica, Robusta and many different provenances
Coffee isn’t just coffee. In addition to the Arabica and Robusta varieties, the respective growing regions – the so-called provenances – also have a major influence on the aroma and appearance of a coffee.
Almost all coffee roasters blend their coffees not only for cost and taste reasons, but also to compensate for natural quality fluctuations and create a desired taste profile. Beans from a wide variety of provenances can be mixed together to achieve the desired character.
The two most important coffee species, Arabica and Robusta, differ in taste, appearance and price. Accordingly, each is also suitable for different areas of application. Robusta, for example, should not be omitted from certain coffees, e.g. espresso, since the beans have a low level of acidity.
With a 61% share of coffee production, Arabica is the best-known coffee plant of them all. Arabica only thrives at altitudes extending to the vegetation line. This is why the plant is often referred to as “highland coffee”.
In South and Central American highlands and East Africa, it can develop an often elegant, subtle and complex aroma.
Tropical areas are optimal for the growth of the Arabica plant, as they offer perfect rain and temperature conditions. This allows Arabica coffee beans to ripen relatively evenly and to be harvested on average once or twice a year.
Coffea Canephora differs greatly from the Arabica plant in taste and, unlike Arabica, displays colourful beans. It is known for its bitter and stringent note and is therefore not suited to every taste. It also has a higher caffeine content in the bean. In total, Robusta accounts for around 25% of coffee production worldwide.
The coffee plant also grows in tropical areas. It finds its optimal growing conditions at a height of 200 to 600 metres.