This important and valuable bean is produced chiefly from Coffea arabica, a Rubiaceous plant indigenous to Abyssinia. The name is probably derived from the Arabic K’hawah, although by some it has been traced to Kaffa, a province in Abyssinia, in which the tree grows wild.
The common Arabian coffee shrub is an evergreen plant, which under natural conditions grows to a height of from 18 to 20 ft., with oblong-ovate, smooth and shining leaves, measuring about 6 in. in length by 22 wide.
The fruit is a fleshy berry, having the appearance and size of a small cherry, and as it ripens it assumes a dark red colour. Each fruit contains two seeds embedded in a yellowish pulp, and the seeds are enclosed in a thin membranous endocarp (the “parchment”).
The seeds are of a soft, semi-translucent, bluish or greenish colour, hard and tough in texture. The regions best adapted for the cultivation of coffee are well-watered mountain slopes at an elevation ranging from 1000 to 4000 ft. above sea-level, within the tropics, and possessing a mean annual temperature of about 65° to 70°F.
The fruits are fully ripe about seven months after the flowers open; the ripe fruits are fleshy, and of a deep red colour, whence the name of “cherry.” When mature the fruits are picked by hand, or allowed to fall of their own accord or by shaking the plant. The subsequent preparation may be according to (1) the dry or (2) the wet method.
- In the dry method the cherries are spread in a thin layer, often on a stone drying floor, or barbecue, and exposed to the sun. Protection is necessary against heavy dew or rain. The dried cherries can be stored for any length of time, and later the dried pulp and the parchment are removed, setting free the two beans contained in each cherry.
- In the wet, or as it is sometimes called, West Indian method, the cherries are put in a tank of water. On large estates galvanized spouting is often employed to convey the beans by the help of running water from the fields to the tank. The mature cherries sink, and are drawn off from the tank through pipes to the pulping machines. Here they are subjected to the action of a roughened cylinder revolving closely against a curved iron plate. The fleshy portion is reduced to a pulp, and the mixture of pulp and liberated seeds (each still enclosed in its parchment) is carried away to a second tank of water and stirred. The light pulp is removed by a stream of water and the seeds allowed to settle. Slight fermentation and subsequent washings, accompanied by trampling with bare feet and stirring by rakes or special machinery, result in the parchment coverings being left quite clean. The beans are now dried on barbecues, in trays, &c., or by artificial heat if climatic conditions render this necessary.
In the process of roasting, coffee seeds swell up by the liberation of gases within – their weight decreasing in proportion to the extent to which the operation is carried. Roasting also develops with the aromatic caffeone above alluded to a bitter soluble principle, and it liberates a portion of the caffeine from its combination with the caffetannic acid.
The roaster must judge of the amount of heat required for the adequate roasting of different qualities, and while that is variable, the range of roasting temperature proper for individual kinds is only narrow.
The roasting of coffee should be done as short a time as practicable before the grinding for use, and as ground coffee especially parts rapidly with its aroma, the grinding should only be done when coffee is about to be prepared.
The desired grinding size depends on the methods of brewing. The finer methods of Turkish, Espresso and Moka Pots generally produce strong and bitter cup. The Chemex Method produces a crisp and clean flavour while the Drip Method produces and light and acidic flavour and the French Press a thicker more wholesome taste.
As a personal preference we tend to prefer the French Press for its deeper flavours that seep into the water during its longer contact time with the coffee.