About Coffee: Fundamentals
The Coffea arabica tree is an evergreen. Its leaves are broad, shiny, and shaped like an arrowhead. They are three to six inches long and line up in pairs on either side of a central stem.
Its flowers are small, white blossoms that cluster at the base of the leaves. In the wild it grows to a height of 14 to 20 feet, but when cultivated it is usually kept pruned to about 6 feet to facilitate picking the beans and to encourage heavy bearing.
When mature the coffee tree's small oval berries are about the color and size of a small cherry. Inside the skin and pulp are nestled two coffee beans with their flat sides together. Each tree can produce between one and twelve pounds of coffee per year, depending on soil, climate, and other factors. The plants are propagated either from seed or from cuttings.
Coffea arabica grows best in conditions where there are no frosts or hot extremes, in fertile, well-watered but well-drained soil, with only two hours a day of direct sunlight. Some growers plant shade trees; or make protective trellises so that they receive sun for only part of the day.
Arabica trees grown at altitudes between 3,000 to 6,000 feet, usually produce coffee with a "hard bean." The colder climate encourages a slower-maturing berry, with a small, dense, less porous bean with less moisture and more flavor.
The best coffees are grown either on small- to medium-sized estates, or on peasant plots. The poorest coffees are peasant-grown or -gathered coffees, either robusta species or low-grown arabicas, that are not properly picked or handled.
Harvesting and Preparation
Coffee berries do not ripen uniformly. The same branch maysimultaneously display ripe red berries, unripe green berries, and overripe black berries. Conscientious growers go over the trees again and again, selecting only the ripe berries. Once coffee is picked, it can be prepared either by a "dry" method, which produces what is called natural coffee, or by the "wet" method, which produces what is termed washed coffee.
In the dry method, the berries are dried, either by exposure to the sun or in a mechanical dryer. The hard, shriveled husk is later stripped off the bean by machine, by soaking and washing with hot water, or with a grindstone or mortar and pestle.
In the wet method, most of the covering is removed from the bean before it is dried. This leaves the beans covered with a sticky substance. The beans are soaked in water, which allows natural enzymes to digest this slimy layer from the bean. This step is called fermentation.
Next, the coffee is washed and then dried, either by the sun in open terraces, or in large mechanical dryers. This leaves two last thin layers covering the bean, the parchment or pergamino and the silver skin. Most often a machine called a huller is used to rub these layers off.
The last step in processing is cleaning. With most high-quality coffees, the beans are placed on conveyor belts or trays and examined by workers who remove defective beans, sticks, dirt, and other debris. The very best coffees may be cleaned twice.
There are four main criteria for grading: how big the bean is, where and at what altitude it was grown, how it was prepared and picked, and how good it tastes, or its cup quality.
Typically, the government of the growing country imposes grading standards to encourage and support quality and to attract and reassure foreign buyers. Coffees may be subject to still another grading or sorting after they reach the United States.