What is robusta coffee? How it differs from arabica

How is robusta different from arabica?

Robusta differs from arabica in how it grows, how much caffeine it has and how it tastes. The two are separate species, not varieties of one plant.

The altitude and caffeine figures come from Perfect Daily Grind, and the sugar figures from Wikipedia. World Coffee Research notes that a single robusta tree "cannot successfully pollinate its own flowers, as arabica trees can do." It also places robusta's high yields at 200 to 800 meters.

Where does robusta come from?

Robusta is native to the humid forests of central and western sub-Saharan Africa. World Coffee Research describes a range running from Guinea to Uganda to Angola.

Commercial growing began around 1870 in Congo, according to World Coffee Research. The botanist Louis Pierre named the species Coffea canephora in 1895. The name "robusta" dates to 1900, when the horticulturist Linden described and sold the plant under it, a nod to its resistance traits.

Its spread had a specific cause. Coffee leaf rust ravaged arabica farms in the late 1800s, and robusta's resistance made it valuable. Today, Wikipedia lists Vietnam as the largest producer, followed by Brazil, Indonesia, India and Uganda.

Why does robusta have more caffeine?

Robusta simply carries more caffeine in the seed, about twice as much as arabica per Perfect Daily Grind. Wikipedia gives 2.7% for robusta against 1.5% for arabica.

Robusta also has less sugar. Wikipedia puts it at 3 to 7%, against 6 to 9% for arabica. Less sugar and more bitter compounds help explain why robusta tastes harsher and less sweet.

If you want a stronger caffeine hit without a bigger dose, a blend with robusta delivers it. If you are sensitive to caffeine, check the label for "100% arabica."

Is robusta always low quality?

No, though most robusta on the market is grown for volume, not flavor. Perfect Daily Grind reports that well-grown robusta can show notes such as cocoa, caramel and walnut, and can reach or even exceed the 90-point mark.

The case for quality also rests on genetics. World Coffee Research splits robusta into two broad genetic groups, Guinean and Congolese, and its catalog lists 47 robusta varieties. That diversity is far less explored than arabica's.

Still, judge each coffee on its own. A cheap supermarket robusta and a carefully processed lot from a quality-focused farm are very different products.

Why is robusta in espresso blends?

Roasters add robusta to espresso blends for caffeine, body and crema. Perfect Daily Grind says it is "often used in blends to add caffeine, crema, and body."

This is most common in Italian-style espresso. Wikipedia describes high-quality robusta giving "a full-bodied taste and a better foam head." If your shot looks thick and tastes chocolatey and slightly bitter, the blend may well include some robusta.

Does robusta need a different grind?

Not as a rule. The brew method sets your starting grind, whatever the species. An espresso blend with robusta starts in the same range as any other espresso, which you can see on BrewMark's espresso settings.

From there, you dial in by taste. If a robusta blend runs bitter, the usual first move is a slightly coarser grind, as you would for any over-extracted shot. If you are choosing gear for espresso blends, the grinder finder narrows the field by method.

For more on the other species, see arabica. For how robusta shows up in the shot itself, see crema.