Coffee

Coffee (Fr: café, Ger. Kaffee). This important and valuable article of food is the produce chiefly of Coffea arabica, a Rubiaceous plant indigenous to Abyssinia, which, however, as cultivated originally, spread outwards from the southern parts of Arabia. The name is probably derived from the Arabic K’hāwah, although by some it has been traced to Kaffa, a province in Abyssinia, in which the tree grows wild.

Fig. 1.—Branch of Coffea arabica.

The genus Coffea, to which the common coffee tree belongs, contains about 25 species in the tropics of the Old World, mainly African. Besides being found wild in Abyssinia, the common coffee plant appears to be widely disseminated in Africa, occurring wild in the Mozambique district, on the shores of the Victoria Nyanza, and in Angola on the west coast. The coffee leaf disease in Ceylon brought into prominence Liberian coffee (C. liberica), a native of the west coast of Africa, now extensively grown in several parts of the world. Other species of economic importance are Sierra Leone coffee (C. stenophylla) and Congo coffee (C. robusta), both of which have been introduced into and are cultivated on a small scale in various parts of the tropics. C. excelsa is another species of considerable promise.

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, acuminate, smooth and shining leaves, measuring about 6 in. in length by 2½ wide. Its flowers, which are produced in dense clusters in the axils of the leaves, have a five-toothed calyx, a tubular five-parted corolla, five stamens and a single bifid style. The flowers are pure white in colour, with a rich fragrant odour, and the plants in blossom have a lovely and attractive appearance, but the bloom is very evanescent. 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”). Between each seed and the parchment is a delicate covering called the “silver skin.” The seeds which constitute the raw coffee “beans” of commerce are plano-convex in form, the flat surfaces which are laid against each other within the berry having a longitudinal furrow or groove. When only one seed is developed in a fruit it is not flattened on one side, but circular in cross section. Such seeds form “pea-berry” coffee.

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 Liberian coffee plant (C. liberica) has larger leaves, flowers and fruits, and is of a more robust and hardy constitution, than Arabian coffee. The seeds yield a highly aromatic and well-flavoured coffee (but by no means equal to Arabian), and the plant is very prolific and yields heavy crops. Liberian coffee grows, moreover, at low altitudes, and flourishes in many situations unsuitable to the Arabian coffee. It grows wild in great abundance along the whole of the Guinea coast.

History.—The early history of coffee as an economic product is involved in considerable obscurity, the absence of fact being compensated for by a profusion of conjectural statements and mythical stories. The use of coffee (C. arabica) in Abyssinia was recorded in the 15th century, and was then stated to have been practised from time immemorial. Neighbouring countries, however, appear to have been quite ignorant of its value. Various legendary accounts are given of the discovery of the beneficial properties of the plant, one ascribing it to a flock of sheep accidentally browsing on the wild shrubs, with the result that they became elated and sleepless at night! Its physiological action in dissipating drowsiness and preventing sleep was taken advantage of in connexion with the prolonged religious service of the Mahommedans, and its use as a devotional antisoporific stirred up fierce opposition on the part of the strictly orthodox and conservative section of the priests. Coffee by them was held to be an intoxicating beverage, and therefore prohibited by the Koran, and severe penalties were threatened to those addicted to its use. Notwithstanding threats of divine retribution and other devices, the coffee-drinking habit spread rapidly among the Arabian Mahommedans, and the growth of coffee and its use as a national beverage became as inseparably connected with Arabia as tea is with China.

Towards the close of the 16th century the use of coffee was recorded by a European resident in Egypt, and about this epoch it came into general use in the near East. The appreciation of coffee as a beverage in Europe dates from the 17th century. “Coffee-houses” were soon instituted, the first being opened in Constantinople and Venice. In London coffee-houses date from 1652, when one was opened in St Michael’s Alley, Cornhill. They soon became popular, and the role played by them in the social life of the 17th and 18th centuries is well known. Germany, France, Sweden and other countries adopted them at about the same time as Great Britain. In Europe, as in Arabia, coffee at first made its way into favour in the face of various adverse and even prohibitive restrictions. Thus at one time in Germany it was necessary to obtain a licence to roast coffee. In England Charles II. endeavoured to suppress coffee-houses on the ground that they were centres of political agitation, his royal proclamation stating that they were the resort of disaffected persons “who devised and spread abroad divers false, malicious and scandalous reports, to the defamation of His Majesty’s government, and to the disturbance of the peace and quiet of the nation.”

Up to the close of the 17th century the world’s entire, although limited, supply of coffee was obtained from the province of Yemen in south Arabia, where the true celebrated Mocha or Mokka coffee is still produced. At this time, however, plants were successfully introduced from Arabia to Java, where the cultivation was immediately taken up. The government of Java distributed plants to various places, including the botanic garden of Amsterdam. The Portuguese introduced coffee into Ceylon. From Amsterdam the Dutch sent the plant to Surinam in 1718, and in the same year Jamaica received it through the governor Sir Nicholas Lawes. Within a few years coffee reached the other West Indian islands, and spread generally through the tropics of the New World, which now produce by far the greater portion of the world’s supply.

Cultivation and Preparation for Market.—Coffee plants are grown from seeds, which, as in the case of other crops, should be obtained from selected trees of desirable characteristics. The seeds may be sown “at stake,” i.e. in the actual positions the mature plants are to occupy, or raised in a nursery and afterwards transplanted. The choice of methods is usually determined by various local considerations. Nurseries are desirable where there is risk of drought killing seedlings in the open. Whilst young the plants usually require to be shaded, and this may be done by growing castor oil plants, cassava (Manihot), maize or Indian corn, bananas, or various other useful crops between the coffee, until the latter develop and occupy the ground. Sometimes, but by no means always, permanent shading is afforded by special shade trees, such as species of the coral tree (Erythrina) and other leguminous trees. Opinions as to the necessity of shade trees varies in different countries; e.g. in Brazil and at high elevations in Jamaica they are not employed, whereas in Porto Rico many look on them as absolutely essential. It is probable that in many cases where shade trees are of advantage their beneficial action may be indirect, in affording protection from wind, drought or soil erosion, and, when leguminous plants are employed, in enriching the soil in nitrogen. The plants begin to come into bearing in their second or third year, but on the average the fifth is the first year of considerable yield. There may be two, three, or even more “flushes” of blossom in one year, and flowers and fruits in all stages may thus be seen on one plant. 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. This primitive and simple method is employed in Arabia, in Brazil and other countries. In Brazil it is giving place to the more modern method described below.

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. Recent experiments in Porto Rico tend to show that if the weather is unfavourable during the crop period the pulped coffee can be allowed to remain moist and even to malt or sprout without injury to the final value of the product when dried later. The product is now in the state known as parchment coffee, and may be exported. Before use, however, the parchment must be removed. This may be done on the estate, at the port of shipment, or in the country where imported. The coffee is thoroughly dried, the parchment broken by a roller, and removed by winnowing. Further rubbing and winnowing removes the silver skin, and the beans are left in the condition of ordinary unroasted coffee. Grading into large, medium and small beans, to secure the uniformity desirable in roasting, is effected by the use of a cylindrical or other pattern sieve, along which the beans are made to travel, encountering first small, then medium, and finally large apertures or meshes. Damaged beans and foreign matter are removed by hand picking. An average yield of cleaned coffee is from 1½ to 2 ℔ per tree, but much greater crops are obtained on new rich lands, and under special conditions.

Coffee Consumption.—The United States of America consume nearly one half of all the coffee exported from the producing countries of the world. This might of course be due merely to the States containing more coffee-drinkers than other countries, but the average consumption per head in the country is about 11 to 12 ℔ per annum, an amount equalled or excelled only in Norway, Sweden and Holland. Whilst one great branch of the Anglo-Saxon stock is near the head of the list, it is interesting to note that the United Kingdom and also Canada and Australia are almost at the foot, using only about 1 ℔ of coffee per head each year. Germany, with a consumption of about 6 to 7 ℔ per person per annum uses considerably less than a quarter of the world’s commercial crop. France, about 5 ℔ per head, takes about one eighth; and Austria-Hungary, about 2 ℔, uses some one-sixteenth. Holland consumes approximately as much, but with a much smaller population, the Dutch using more per head than any other people—14 ℔ to 15 ℔ per annum. Their taste is seen also in the relatively high consumption in South Africa. Sweden, Belgium and the United Kingdom, follow next in order of total amount used.

In many tropical countries much coffee is drunk, but as it is often produced locally exact figures are not available. The average consumption in the United Kingdom is about 50,000,000 lb per annum; about one-fifth only is produced in the British empire, and of this about nineteen-twentieths come from India and one-twentieth from the British West Indies.

Coffee-leaf Disease.—The coffee industry in Ceylon was ruined by the attack of a fungoid disease (Hemileia vastatrix) known as the Ceylon coffee-leaf disease. This has since extended its ravages into every coffee-producing country in the Old World, and added greatly to the difficulties of successful cultivation. The fungus is a microscopic one, the minute spores of which, carried by the wind, settle and germinate upon the leaves of the plant. The fungal growth spreads through the substance to the leaf, robbing the leaf of its nourishment and causing it to wither and fall. An infected plantation may be cleansed, and the fungus in its nascent state destroyed, by powdering the trees with a mixture of lime and sulphur, but, unless the access of fresh spores brought by the wind can be arrested, the plantations may be readily reinfected when the lime and sulphur are washed off by rain. The separation of plantations by belts of trees to windward is suggested as a check to the spread of the disease.

Microscopic Structure.—Raw coffee seeds are tough and horny in structure, and are devoid of the peculiar aroma and taste which are so characteristic of the roasted seeds. The minute structure of coffee allows it to be readily recognized by means of the microscope, and as roasting does not destroy its distinguishing peculiarities, microscopic examination forms the readiest means of determining the genuineness of any sample. The substance of the seed, according to Dr Hassall, consists “of an assemblage of vesicles or cells of an angular form, which adhere so firmly together that they break up into pieces rather than separate into distinct and perfect cells. The cavities of the cells include, in the form of little drops, a considerable quantity of aromatic volatile oil, on the presence of which the fragrance and many of the active principles of the berry depend” (see fig. 3).

Fig. 3.—Microscopic structure of Coffee.

Physiological Action.—Coffee belongs to the medicinal or auxiliary class of food substances, being solely valuable for its stimulant effect upon the nervous and vascular system. It produces a feeling of buoyancy and exhilaration comparable to a certain stage of alcoholic intoxication, but which does not end in depression or collapse. It increases the frequency of the pulse, lightens the sensation of fatigue, and it sustains the strength under prolonged and severe muscular exertion. The value of its hot infusion under the rigours of Arctic cold has been demonstrated in the experience of all Arctic explorers, and it is scarcely less useful in tropical regions, where it beneficially stimulates the action of the skin.

The physiological action of coffee mainly depends on the presence of the alkaloid caffeine, which occurs also in tea, Paraguay tea, and cola nuts, and is very similar to theobromine, the active principle in cocoa. The percentage of caffeine present varies in the different species of Coffea. In Arabian coffee it ranges from about 0.7 to 1.6%; in Liberian coffee from 1.0 to 1.5%. Sierra Leone coffee (C. stenophylla) contains from 1.52 to 1.70%; in C. excelsa 1.89% is recorded, and as much as 1.97% in C. canephora. Four species have been shown by M. G. Bertrand to contain no caffeine at all, but instead a considerable quantity of a bitter principle. All these four species are found only in Madagascar or the neighbouring islands. Other coffees grown there contain caffeine as usual. Coffee, with the caffeine extracted, has also been recently prepared for the market. The commercial value of coffee is determined by the amount of the aromatic oil, caffeone, which develops in it by the process of roasting. By prolonged keeping it is found that the richness of any seeds in this peculiar oil is increased, and with increased aroma the coffee also yields a blander and more mellow beverage. Stored coffee loses weight at first with great rapidity, as much as 8% having been found to dissipate in the first year of keeping, 5% in the second, and 2% in the third; but such loss of weight is more than compensated by improvement in quality and consequent enhancement of value.

Roasting.—In the process of roasting, coffee seeds swell up by the liberation of gases within their substance,—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. Roasting is an operation of the greatest nicety, and one, moreover, of a crucial nature, for equally by insufficient and by excessive roasting much of the aroma of the coffee is lost; and its infusion is neither agreeable to the palate nor exhilarating in its influence. 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. In continental countries it is the practice to roast in small quantities, and thus the whole charge is well under the control of the roaster; but in Britain large roasts are the rule, in dealing with which much difficulty is experienced in producing uniform torrefaction, and in stopping the process at the proper moment. The coffee-roasting apparatus is usually a malleable iron cylinder mounted to revolve over the fire on a hollow axle which allows the escape of gases generated during torrefaction. 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.

Adulteration.—Although by microscopic, physical and chemical tests the purity of coffee can be determined with perfect certainty, yet ground coffee is subjected to many and extensive adulterations (see also Adulteration). Chief among the adulterant substances, if it can be so called, is chicory; but it occupies a peculiar position, since very many people on the European continent as well as in Great Britain deliberately prefer a mixture of chicory with coffee to pure coffee. Chicory is indeed destitute of the stimulant alkaloid and essential oil for which coffee is valued; but the facts that it has stood the test of prolonged and extended use, and that its infusion is, in some localities, used alone, indicate that it performs some useful function in connexion with coffee, as used at least by Western communities. For one thing, it yields a copious amount of soluble matter in infusion with hot water, and thus gives a specious appearance of strength and substance to what may be really only a very weak preparation of coffee. The mixture of chicory with coffee is easily detected by the microscope, the structure of both, which they retain after torrefaction, being very characteristic and distinct. The granules of coffee, moreover, remain hard and angular when mixed with water, to which they communicate but little colour; chicory, on the other hand, swelling up and softening, yields a deep brown colour to water in which it is thrown. The specific gravity of an infusion of chicory is also much higher than that of coffee. Among the numerous other substances used to adulterate coffee are roasted and ground roots of the dandelion, carrot, parsnip and beet; beans, lupins and other leguminous seeds; wheat, rice and various cereal grains; the seeds of the broom, fenugreek and iris; acorns; “negro coffee,” the seeds of Cassia occidentalis, the seeds of the ochro (Hibiscus esculentus), and also the soja or soy bean (Glycine Soya). Not only have these with many more similar substances been used as adulterants, but under various high-sounding names several of them have been introduced as substitutes for coffee; but they have neither merited nor obtained any success, and their sole effect has been to bring coffee into undeserved disrepute with the public.

Not only is ground coffee adulterated, but such mixtures as flour, chicory and coffee, or even bran and molasses, have been made up to simulate coffee beans and sold as such.

The leaves of the coffee tree contain caffeine in larger proportion than the seeds themselves, and their use as a substitute for tea has frequently been suggested. The leaves are actually so used in Sumatra, but being destitute of any attractive aroma such as is possessed by both tea and coffee, the infusion is not palatable. It is, moreover, not practicable to obtain both seeds and leaves from the same plant, and as the commercial demand is for the seed alone, no consideration either of profit or of any dietetic or economic advantage is likely to lead to the growth of coffee trees on account of their leaves.

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