Coffee plant

Coffee is the common name for the very important genus Coffea, Rubiaceae, containing about 90 species. Coffea arabica L., (‘Typica’) constitutes about 80 per cent of cultivated coffee and Coffea canephora (‘Robusta’), cultivated mostly in western Africa.

In India, Coffea arabica (Arabian coffee), Coffea liberica Bull ex Hiern (Liberian coffee), Coffea robusta Linden (=Coffea laurentii de Wilde) (Congo coffee) and Coffea stenophylla G. Don (Sierra Leone Coffee) are cited as cultivated. It is often not possible to know the species in cultivation in a particular area, since such botanical details are of no interest to the coffee planter. It is usually assumed that it is Coffea arabica, but with both sexual and graft hybrids being in abundance, one can never be sure, unless the breeder provides the pedigree.

Coffea arabica is considered to have originated in the Ethiopian highlands and was taken to the Yemen in Arabia, where it was first cultivated. Although coffee is now commercially grown throughout the tropics, Central and South America and Brazil account for more than half of the world’s coffee production. In India the state of Karnataka has a major share in coffee production while it is also cultivated in the other southern states, but do not figure in any of the world’s quality statistics.

Coffee plants produce white flowers in abundance and are a pretty sight when in flowering (Coffee1), and also when the fruits are ripe and red (Coffee2). Ripe coffee fruits are sun dried and hulled to release the beans (seeds) that are again sun dried. At some time during the drying process, coffee seeds acquire their characteristic flavour and quality. Caffeol, an oil, is the principal component which confers upon coffee beans their characteristic flavour when roasted. The roasted beans are ground, from which the coffee decoction is brewed.

The beans also contain the alkaloid caffeine (1 to 2 per cent) which is responsible for the stimulatory action of the beverage. Caffeine or theine is found in a variety of plants, many of which are used in making beverages. Tea (see Camellia sinensis) and cocoa (see Theobroma cacao) are the other common beverage plants. Caffeine stimulates circulation and the brain, giving a feeing of relief from fatigue. Coffee is also a diuretic and reduces the effects of alcohol.

The chemistry of coffee is very complex and over 1,000 different compounds have been recorded. In addition to caffeine and caffeol, adenine, xanthine, hyuooxanthine and guanine, and the alkaloid tigonelline are also reported, from coffee.