Coffee - biology.

Coffee - biology. I INTRODUCTION Coffee, common name for any of a genus of trees of the madder family, and also for their seeds (beans) and for the beverage brewed from them. Of the 30 or more species of the genus, only three are important: Arabian, robusta, and Liberian. The shrub or small tree, 4.6 to 6 m (15 to 20 ft) high at maturity, bears shiny green, ovate leaves that persist for three to five years and white, fragrant flowers that bloom for only a few days. During the six or seven months after appearance of the flower, the fruit develops, changing from light green to red and, ultimately, when fully ripe and ready for picking, to deep crimson. The mature fruit, which resembles a cherry, grows in clusters attached to the limb by very short stems, and it usually contains two seeds, or beans, surrounded by a sweet pulp. Coffee grows well on the islands of Java and Sumatra and in Arabia, India, Africa, the West Indies, and South and Central America. The Americas, where Arabian coffee is grown, produce approximately two-thirds of the world's supply. II PRODUCTION The soil in which coffee is grown must be rich, moist, and absorbent enough to accept water readily, but sufficiently loose to allow rapid drainage of excess water. The best soil is composed of leaf mold, other organic matter, and disintegrated volcanic rock. Although coffee trees are damaged easily by frost, they are cultivated in cooler regions. The growing temperatures range from 13° to 26° C (55° to 80° F). Altitudes of coffee plantations range from sea level to the tropical frost level, about 1,800 m (about 6,000 ft). Robusta coffee and Liberian coffee grow best at altitudes below 900 m (3,000 ft); Arabian coffee flourishes at the higher altitudes. The seeds are planted directly in the field or in specially prepared nurseries. In the latter case, young selected plants are transplanted later to the fields. Commercial fertilizers are used extensively to promote the growth of stronger, healthier trees with heavier yields. Both the trees and the fruit are subject to insect infestation and microbial diseases, which may be controlled by spraying and proper agricultural management. A Harvesting The coffee tree produces its first full crop when it is about five years old. Thereafter it produces consistently for 15 or 20 years. Some trees yield 0.9 to 1.3 kg (2 to 3 lb) of marketable beans annually, but 0.45 kg (1 lb) is considered an average annual yield. Two methods of harvesting are used. One is based on selective picking; the other involves shaking the tree and stripping the fruit. Beans picked by the first technique are generally processed, if water is available, by the so-called wet method, in which the beans are softened in water, depulped mechanically, fermented in large tanks, washed again, and finally dried in the open or in heated, rotating cylinders. The so-called dry method, used generally for beans harvested by the second technique, entails only drying the beans and removing the outer coverings. In either case the final product, called green coffee, is sorted by hand or machine to remove defective beans and extraneous material and is then graded according to size. B Commercial Crops The major types of commercial coffee are the arabicas and the robustas. In the western hemisphere the arabicas are subdivided into Brazils and milds. Robustas are produced in the eastern hemisphere exclusively, together with substantial quantities of arabicas. The Brazils consist principally of Santos, Paraná, and Rio, named for the ports from which they are shipped. Milds are identified by the names of countries or districts in which they are grown, such as Medellín, Armenia, and Manizales coffees from Colombia. Robustas and other arabicas are similarly identified. Green coffee is a major import of the United States; about two-thirds of the 1.2 million metric tons comes from Central and South America, with Brazil and Colombia the two largest suppliers. Several varieties of green coffee usually are blended and roasted together to produce the tastes, aromas, and flavors popular with consumers. As a rule the beans are heated in rotating, horizontal drums that provide a tumbling action to prevent uneven heating or scorching. Temperatures for roasting range from about 193° C (about 380° F) for a light roast, through about 205° C (about 400° F) for a medium roast, to about 218° C (about 425° F) for a dark roast. The roasted beans are cooled rapidly. Roasted coffee may be packaged and shipped to retail stores, which custom grind it for the customers on purchase, or it may be ground in plate- or roller-type grinding mills before shipment. Ground coffee loses its unique flavor within about a week unless it is specially packaged. Plastic-and-paper combinations are popular packaging media that afford protection to freshly roasted and ground coffee. Hermetically sealed vacuum, or pressure, cans keep coffee fresh for up to three years. III CHARACTERISTICS Coffee contains a complex mixture of chemical components of the bean, some of which are not affected by roasting. Other compounds, particularly those related to the aroma, are produced by partial destruction of the green bean during roasting. Chemicals extracted by hot water are classified as nonvolatile taste components and volatile aroma components. Important nonvolatiles are caffeine, trigonelline, chlorogenic acid, phenolic acids, amino acids, carbohydrates, and minerals. Important volatiles are organic acids, aldehydes, ketones, esters, amines, and mercaptans. The principal physiological effects of coffee are due to caffeine, an alkaloid that acts as a mild stimulant. In recent years controversy arose over the possibly harmful effects of coffee beyond those recognized for people who should take few or no stimulants, and the dangers of caffeine for the fetuses of pregnant women. These debated studies were not substantiated, however. A Soluble Coffee Soluble or instant coffee is an important production of the United States coffee industry. In its manufacture an extract is prepared by mixing coarsely ground and roasted coffee with hot water. The water is evaporated from the extract by various methods, including the use of spray driers or high-vacuum equipment. In freezedried coffee the coffee extract is frozen, and the water is removed by sublimation. The product is packed in vacuumized, sealed jars or in cans. B Decaffeinated Coffee Caffeine can be removed from coffee by treating the green beans with chlorinated hydrocarbon solvents. The beans are roasted by ordinary procedures after removal of the solvents. Decaffeinated coffee is used by people hypersensitive to the caffeine present in regular coffee. In the 1980s nonchemical methods of decaffeination became more common. C Coffee Substitutes The use of substitutes for coffee in the United States is limited. The most important substitute is chicory, although chicory is usually used as an extender. Under United States law, the addition of chicory or any other substance must be clearly stated on the brand label. IV HISTORY Exactly where and when coffee was first cultivated is not known, but some authorities believe that it was grown initially in Arabia near the Red Sea about AD675. Coffee cultivation was rare until the 15th and 16th centuries, when extensive planting of the tree occurred in the Yemen region of Arabia. The consumption of coffee increased in Europe during the 17th century, prompting the Dutch to cultivate it in their colonies. In 1714 the French succeeded in bringing a live cutting of a coffee tree to the island of Martinique in the West Indies. This single plant was the genesis of the great coffee plantations of Latin America. Because of the economic importance of coffee exports, a number of Latin American countries made arrangements before World War II (1939-1945) to allocate export quotas so that each country would be assured a certain share of the United States coffee market. The first coffee quota agreement was arranged in 1940 and was administered by an Inter-American Coffee Board. The idea of establishing coffee export quotas on a worldwide basis was adopted in 1962, when an International Coffee Agreement was negotiated by the United Nations. During the five-year period when this agreement was in effect, 41 exporting countries and 25 importing countries acceded to its terms. The agreement was renegotiated in 1968, 1976, and 1983. Participating nations failed to sign a new pact in 1989, however, and world coffee prices plunged. Scientific classification: Coffee makes up the genus Coffea of the family Rubiaceae. Arabian coffee is classified as Coffea arabica, robusta coffee as Coffea canephora, and Liberian coffee as Coffea liberica. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.