Coffee is usually prepared as a defined blend of beans, these having been sourced from certain types of coffee plants.
The most common are beans from the Coffea robusta and Coffea arabica plant, while Coffea excelsa and Coffea liberica tend to be far rarer. Consequently, these two basic types - arabica and robusta - are the primary basis for blends.
Arabica (approx. 70% of global production) contains less caffeine of the two and a wider range of delicate flavours and aromas. Another difference is that it’s cultivated at higher altitudes (900–2800m), often in volcanic soil or forests (e.g. Ethiopia’s Harar or Wild Forest).
In contrast, robusta beans are larger, and during processing and roasting are extremely sensitive to temperature. However, the robusta plant is easier to grow. Robusta’s share of global production stands at approximately 25%, the foremost producers being Brazil, Vietnam, Columbia and Indonesia. The coffee has an earthier, stronger flavour and contains about twice as much caffeine as arabica.
Interestingly, coffee is second only to oil as the most widely sold commodity globally.