Coffea canephora — C. canephora var. robusta
Most of the world’s robusta is grown in Central and Western Africa, parts of Southeast Asia, including Indonesia and Vietnam, and in Brazil. Production of robusta is increasing, though it accounts for only about 30 percent of the world market. Genetically, robusta carries fewer chromosomes than arabica and the bean itself tends to be slightly rounder and smaller than an arabica bean. The robusta tree is heartier, more disease and parasite resistant, which makes it easier and cheaper to cultivate. It also has the advantage of being able to withstand warmer climates, preferring constant temperatures between 75 and 85 degrees, which enables it to grow at far lower altitudes than arabica. It requires about 60 inches of rainfall a year and cannot withstand a frost. Compared with arabica, robusta beans produce a coffee which has a distinctive taste and about 50-60% more caffeine. Robusta is primarily used in blends and for instant coffees.
The Anatomy of a Coffee Cherry
The coffee cherry’s outer skin is called the exocarp. Beneath it is the mesocarp, a thin layer of pulp, followed by a slimy layer called the parenchyma. The beans themselves are covered in a parchment-like envelope named the endocarp, more commonly referred to as ‘the parchment.’ Inside the parchment, side-by-side lie two beans, each covered separately by yet another layer of thin membrane. The biological name for this membrane or seed skin is thespermoderm, but it is generally referred to in the coffee trade as the ‘silver skin.’