Coffee seed types
There are two main species of the coffee plant, Coffea arabica being the older one. Coffee is thought to be indigenous to south-western Ethiopia, specifically from Kaffa, from which it may have acquired its name. While more susceptible to disease, it is considered by most to taste better than the second species, Coffea canephora (robusta). Robusta, which contains about 40-50% more caffeine, can be cultivated in environments where arabica will not thrive and probably originated in Uganda. This has led to its use as an inexpensive substitute for arabica in many commercial coffee blends. Compared to arabica, robusta tends to be bitter and has little flavor, with a telltale "burnt rubber" or "wet cardboard" aroma and flavor. Good quality robustas are used in some espresso blends to provide a better "crema" (foamy head), and to lower the ingredient cost. In Italy, many espresso blends are based on dark-roasted robusta. The large industrial roasters use a steam treatment process to remove undesirable flavors from robusta beans for use in mass-marketed coffee blends. Other species include Coffea liberica and Coffea esliaca, believed to be indigenous to Liberia and southern Sudan respectively.
Arabica coffees were traditionally named by the port they were exported from, the two oldest being Mocha, from Yemen, and Java, from Indonesia. The modern coffee trade is much more specific about origin, labeling coffees by country, region, and sometimes even the producing estate. Varietal is a botanical term denoting a taxonomic category ranking below species, a designation more specific than arabica or robusta and unrelated to the coffee's place of origin. Coffees consisting entirely of beans from a single varietal, bourbon, for example, are generally referred to as such, along with a reference to their place of origin (as in: Rwanda Blue Bourbon). Coffee aficionados may even distinguish auctioned coffees by lot number.
Most arabica coffee beans originate from one of three growing regions; Latin America, East Africa/Arabia and Asia/Pacific. Beans from different countries or regions usually have distinctive characteristics such as flavor (flavor criteria include terms such as "citrus-like" or "earthy"), aroma (sometimes "berry-like" or "flowery"), body or mouthfeel, and acidity. Acidity refers to a tangy or clean-tasting quality, typically present in washed or wet processed coffees. It does not refer to a coffee's pH level. (Black coffee has a pH of around 5). These distinguishing taste characteristics are dependent not only on the coffee's growing region, but also on its method of process and genetic subspecies or varietal.
A peaberry, (also sometimes called a "Caracoli" bean) is a coffee bean that that develops singly inside the coffee cherry instead of the usual pair of beans. This situation occurs 5-10% of the time. Since flavour is concentrated when only a single bean is grown inside the cherry, these beans (especially Arabica) are highly prized.