Arabica and Robusta — how do the two leading coffee species differ?

Arabica and Robusta dominate world coffee production. Why are they so popular? How do they differ, where are they grown, and can you taste the difference? And which one contributes to the foam on an espresso?

Have you ever wondered about the history and origin of the beans in your cup? You were probably served Arabica, Robusta or a blend of the two.

They differ in cultivation, bean appearance, flavour and caffeine content. Arabica is particularly prized for its aromatic range; Robusta is generally easier to grow. For both, the eventual flavour also depends on soil, elevation, temperature, sunshine, rainfall, processing and roasting.

Can you recognise the beans?

Arabica beans are typically somewhat elongated and flatter, while Robusta beans tend to be smaller and rounder. Green-bean colours vary, with greenish to greyish shades depending on the coffee and processing.

Robusta is cultivated across tropical regions, with major production in Vietnam, Brazil, Uganda and Cameroon. It is generally hardier and can grow at lower elevations.

Arabica is more demanding. Many favourable growing areas lie around 1,000–2,000 metres above sea level, with suitable humidity and temperatures broadly within 15–30°C, depending on local conditions. Producing regions include Brazil, Ethiopia, Indonesia, Yemen and many others.

There is also a difference invisible to the eye: Arabica typically has 44 chromosomes, while Robusta has 22. That is a botanical distinction, not a complete explanation of their different growing requirements. Robusta is generally more resistant to some pests and diseases.

Do they taste different?

Yes. Even less experienced drinkers can often notice the difference. Arabica is commonly associated with a gentler, more aromatic cup, sometimes showing spice, chocolate, fruit or floral notes.

Robusta tends to be more forceful, bitter and astringent. It also usually contains more caffeine, so it can contribute a stronger stimulating effect.

Which is better? That depends on taste. Some prefer delicate Arabica; others enjoy Robusta's intensity. In espresso, Robusta often helps produce a rich crema, although Arabica can form crema too.

Many café coffees combine the two in different proportions. A coffee labelled Arabica may itself be a blend of several origins or varieties. Which do you prefer?

Photo by Ruben Alexander via Flickr, under a Creative Commons licence.