Coffee is a widely consumed stimulant beverage prepared from roasted seeds, commonly called beans, of the coffee plant. Coffee use can be traced at least to as early as the 9th century, when it appeared in the highlands of Ethiopia. According to legend, Ethiopian shepherds were the first to observe the influence of the caffeine in coffee beans when the goats appeared to "dance" and to have an increased level of energy after consuming wild coffee berries. The legend names the shepherd "Kaldi."
From Ethiopia, coffee spread to Egypt and Yemen, and by the 15th century, it had reached the rest of the Middle East, Persia, Turkey, and northern Africa. From the Muslim world, coffee spread to Italy, then to the rest of Europe and the Americas. Today, coffee is one of the most popular beverages worldwide.
Coffee berries, which contain the coffee bean, are produced by several species of small evergreen bush of the genus Coffea. The two most commonly grown species are Coffea canephora (also known as Coffea robusta) and Coffea arabica. These are cultivated in Latin America, Southeast Asia, and Africa. Once ripe, coffee berries are picked, processed, and dried. The seeds are then roasted, undergoing several physical and chemical changes. They are roasted to various degrees, depending on the desired flavor. They are then ground and brewed to create coffee.
Coffee berries and their seeds undergo multi-step processing before they become the roasted coffee with which most consumers are familiar. First, coffee berries are picked, generally by hand. Then, the flesh of the berry is removed, usually by machine, and the seeds–usually called beans–are fermented to remove the slimy layer of mucilage still present on the bean. When the fermentation is finished, the beans are washed to remove the fermentation residue. Finally the seeds are dried and sorted and labeled as green coffee beans.
The next step in the process is the roasting of the green coffee. Coffee is usually sold in a roasted state, and all coffee is roasted before it is consumed. The roasting process influences the taste of the beverage by changing the coffee bean both physically and chemically. The bean decreases in weight as moisture is lost but increases in volume, causing it to become less dense. The actual roasting begins when the temperature inside the bean reaches 392°F, though different varieties of beans differ in moisture and density and therefore roast at different rates. During roasting, carmelization occurs as intense heat breaks down starches in the bean, changing them to simple sugars that begin to brown, changing the color of the bean. During roasting, aromatic oils, acids, and caffeine weaken, changing the flavor, and other oils develop, affecting especially the aroma.
