Coffee, N. F. IV. Coffea Tosta. Roasted Coffee. Caffea. Semen Caffeae. Cafe, Fr. Caffee, G. Caffe, It. Cafe, Sp. Bun, Ar. Copi Cotta, Cingalese. Kaeva, Malay.—The N. F. describes it as "the dried ripe seeds of Coffea arabica Linne or Coffea liberica Bulliard (Fam. Rubiaceae), roasted until they develop a dark brown color and a characteristic aroma, and yielding not less than 1 per cent. of caffeine." N. F.
The C. arabica is a small evergreen tree from fifteen to thirty feet in height; native of Southern Arabia and Abyssinia, but cultivated in many parts of the world. The coffee berry is globular, umbilicate at top, at first green, then red, and ultimately dark purple. It is about as large as a cherry, and contains two seeds surrounded by a paper-like membrane, and enclosed in a yellowish-purple matter. These seeds, divested of their coverings, constitute coffee. The Coffee grains as seen in commerce are oval, having one side strongly convex, the other flat with a longitudinal groove upon the flat side and showing traces of the papery seed coat in the cleft. It has a characteristic aroma and a pleasantly bitter taste. About the year 1690 it was introduced by the Dutch into Java, and in 1718 into their colony of Surinam. Soon after this latter period the French succeeded in introducing it into their West India Islands, Cayenne, and the Isles of France and Bourbon.
The tree is raised from the seeds, which are sown in a soil properly prepared, and, germinating in less than a month, produce plants which, at the end of the year, are large enough to be transplanted. These are then set out in rows at suitable distances, and in three or four years begin to bear fruit. It is said that they continue productive for from thirty to forty years. Though almost always covered with flowers and fruit, they yield most largely at two seasons, and thus afford two harvests during the year. Various methods are employed for freeing the seeds from their coverings; but that considered the best is, by means of machinery, to remove the fleshy portion of the fruit, leaving the seeds surrounded only by their papyraceous envelope, from which they are separated by peeling and winnowing mills. They appear in commerce as "oval, of variable size, having one side strongly convex, the other flat with a longitudinal groove, and showing traces of the papery seed coat in, the cleft. It has a characteristic aroma and a pleasantly bitter taste. Percolate 1 Gm. of powdered Coffee with ether until exhausted and evaporate the percolate to dryness; the residue weighs not less than 0.1 Gm. (presence of at least 10 per cent. of fat). Boil 1 Gm. of powdered Coffee with 10 mils of distilled water, filter and acidify the filtrate with one mil of diluted sulphuric acid, and then decolorize it by the cautious addition of potassium permanganate T.S. This decolorized solution shows no blue coloration upon the addition of iodine T.S. (starch). Shake 1 Gm. of Coffee with 20 mils of water; the strained liquid shows no colored or heavy deposit. Shake 1 Gm. of Coffee with 20 mils of alcohol; the strained liquid shows no colored or heavy deposit, nor is any color imparted to the alcohol (artificial colors or facings). Powdered Coffee, when examined under the microscope, exhibits numerous fragments of the seed coat made up of parenchyma and irregular stone cells, the latter from 0.2 to 1 mm. in length and from 0.015 to 0.05 mm. in width with walls having simple pores; numerous brownish endosperm cells having porous walls about 0.01 mm. in thickness and containing oil and aleurone grains; starch grains few or absent. Coffee yields not less than 3 per cent. nor more than 5 per cent. of ash." N. F.
Assay.—"To 6 Gm. of Coffee, in No. 60 powder, contained in a small flask, add 50 mils of purified petroleum benzin and agitate the mixture occasionally during one hour. Then allow it to settle and decant the benzin solution. Add 50 mils more of the petroleum benzin, shake the mixture occasionally during fifteen minutes, then filter off the benzin and dry the drug. Now transfer the Coffee residue to a bottle having a capacity of about 250 mils and pour upon it 120 mils of chloroform and 6 mils of ammonia water. Stopper the bottle securely and shake it vigorously at intervals during six hours. Then allow it to stand one hour, and filter off 100 mils of the chloroform solution. Transfer this to a beaker and evaporate the chloroform at a gentle heat. Dissolve the alkaloidal residue in 10 mils of a mixture of 1 mil of diluted sulphuric acid and 9 mils of distilled water, by aid of a gentle heat, and filter the solution through a small filter, not exceeding 5 cm. in diameter, into a separator. Wash the beaker and filter with successive small portions of acidulated water, until a few drops of the filtrate give no test for caffeine when tested with iodine T.S. To the mixed acid washings, add a slight excess of ammonia water, and shake out the caffeine with successive portions of chloroform, collecting the chloroformic solutions in a tared flask or beaker. Evaporate or distil off the chloroform at a temperature not exceeding 75° C. (167° F.) and add to the residue 5. mils of ether. Evaporate off the ether cautiously, then dry the residue to constant weight at a temperature not exceeding 80° C. (176° F.) and add 0.0025 Gm. to the final weight of caffeine to replace that lost in the petroleum benzin washing. The weight represents the amount of caffeine in 5 Gm. of Coffee." N. F.
In recent years, because of the spread of a leaf disease, the cultivation of the more hardy Coffea liberica has been undertaken in the Island of Ceylon. This may be distinguished from the C. arabica by the fact that the corolla is nine-cleft in the Liberian and from four to five-cleft in the Arabian. The seeds of the Liberica plant are much larger than those of the Arabica; are not greenish and have the groove deeply wrinkled along its edges.
The annual production of coffee for the world is about one million tons, of which the American countries produce in the neighborhood of nine-tenths, Brazil giving to commerce three-fourths of the world's supply. After South America, the chief producer of coffee is Java, that island sending into commerce nearly twice as much as the remaining Asiatic countries. The amount of coffee entering commerce from Africa is small. The character of coffee varies greatly, not only with the climate in which it is grown but with the circumstances of its cultivation and the character of the stock which produces it. The most esteemed varieties are those which are known as Mocha, and Java, but probably the bulk of the berry retailed as Mocha or Java is of South American origin. Coffee improves by age, losing a portion of its strength and acquiring a more agreeable flavor. It is said to be much better when allowed to ripen perfectly on the tree than as usually collected. The grains should be hard, and should readily sink in water. When soft, light, black or dark colored, or musty, they are inferior.
The composition is very complex. The principal constituents are (1) caffeine (identical with theine), (2) caffetannic acid, (3) fat, (4) carbohydrates, (5) albumenoids, (6) essential oil and aromatic substances. Parry (Food and Drugs, vol. I, 1911, p. 31) gives the following comparative figures for coffee before and after roasting:
|Raw (per cent.)||Roasted (per cent.)|
Among the adulterations of roasted coffee are the roasted or ground cereals; these are readily detected microscopically as well as by the positive reaction for starch in the decoction, which has been cautiously decolorized by the addition of potassium permanganate solution followed by diluted sulphuric acid. Coffee naturally contains no starch.
Chicory, dandelion and other similar roots used as adulterants may be detected microscopically, but a chemical method of detection has been proposed by LaWall and Forman (A. J. P., lxxxv, p. 537 and J. A. Ph. A., iii, p. 1669), which depends upon the determination of the ratio of reducing sugars to extractive matter in the aqueous decoction.
Mussaenda coffee, so called, is not a true coffee; but the seeds of Gaertnera vaginata Lam. (Fam. Loganiaceae). (P. J., Nov., 1889.)
Coffee has a faint peculiar odor and a slightly sweetish, somewhat harsh taste. The sugar which is present is a reducing sugar, probably glucose, and is almost completely caramelized in the roasting process. Caffetannic acid has been ascertained by Hlasiwetz to be a glucoside with the formula C14H8O7 and resolvable into glucose and a peculiar crystallizable acid, C8H8O4, named by him caffeic acid (J. P. C., 1867, 307), and which may be obtained from coffee by boiling a solution of the extract with potassium hydroxide, treating the resulting liquid with sulphuric acid in excess, and extracting the caffeic acid with ether, which yields it somewhat impure by evaporation. (Ibid., January, 1868, 75.) Caffeic acid has the constitution of a dihydroxy-cinnamic acid, and on fusion with potassium hydroxide yields protocatechuic and acetic acids. The coffee fat, which ranges in different varieties from 14 to 21 per cent., is, when purified, white, without odor, of a buttery consistence, melting at 37.5° C. (100° F.), and becomes rancid on exposure. According to Rochleder (Wien. Akad. Ber., xxiv, 40), it contains glycerides of palmitic acid and of an acid of the composition C13H24O2.
The caffeine, according to Payen, is present partly free and partly as a potassium and caffeine chlorogenate, but H. Gorter (Lieb. Annal., ccclix, 217, ccclxii, 237), in investigations made upon Liberian coffee, stated that caffeine does not exist free in coffee, but is all combined. The compound is given the following formula: C32H36C19K2(C8H10O12N4)2+ 2H2O. It decomposes at 225° C. (437° F.), without melting. The yield is 3.3 per cent. The salt is scarcely decomposed by dry chloroform, but is easily decomposed by the presence of water and then gives up its caffeine. This explains the fact observed by the manufacturers of decaffeinated coffees, that dry coffee yields only a small amount of its caffeine to chloroform, but that the extraction takes place readily and almost completely if the coffee is simultaneously treated with water or steam.
Chlorogenic acid is given the formula, C32H38O19, and is a colorless, crystalline compound melting at 206° 0. (402.8° F.), and with a marked laevorotatory power. It is hydrolized by alkalies into caffeic and quinic acids. When strongly heated it emits an odor of roasted coffee and by some is believed to be the principle to which the flavor of the beverage is to be attributed. It is stated that when acted on by sulphuric acid and manganese dioxide it is converted into quinone, being in this respect analogous to quinic acid. Another acid was found which the author named coffalic acid. The coffee also contained citric acid, trigonelline, a pectin and an oxydase.
Julian E. Walter gives the following results of the analyses of several kinds of unroasted coffee: Java, 0.89 per cent. caffeine; Liberian Java, 1.08 per cent. caffeine; Costa Rica, 1.24 per cent. caffeine; Mocha, 0.54 per cent. caffeine; Pea-berry or Fenroll, 0.77 per cent. caffeine; Rio, 1.12 per cent. caffeine. (Ph. Rec., May 5, 1890, 176.) Bertrand (Bull. des Sci. Pharm., iv ) gives the following results of studies of the percentage of caffeine in various coffee berries: In Coffea arabica the percentage varied from 0.69 to 1.60. Of species other than the (C. arabica, C. canephora was found to be the richest in alkaloid, the berries yielding 1.97 per cent., while those of the C. humboldtiana, Baill., were remarkable by reason of their containing a bitter principle, cafamarin, but no caffeine at all, the berries of C. mauritiana contained only 0.07 per cent.
During the roasting process coffee swells to almost double its original volume, losing from 10 to 23 per cent. of its weight (Ph. Cb., 1850, 687), and acquires a new, peculiar odor and a bitter taste. An active empyreumatic oil (caffeol, C8H10O2) is developed during the process, probably at the expense of a portion of the caffeine. Much of the alkaloid, however, escapes change, and a portion of it is volatilized. The excellence of the flavor of roasted coffee depends much upon the manner in which the process is conducted, and the extent to which it is carried. It should be performed in a covered vessel, over a moderate fire, and the grains should be kept in constant motion. When they have acquired a chestnut-brown color, the process should cease. If too long continued, it renders the coffee bitter and acrid, or, by reducing it to charcoal, deprives it entirely of flavor. During a severe roasting the coffee loses a portion of caffeine, which sublimes, while in a slight roasting it loses none; yet 'ordinary coffee for drinking, prepared by percolation, contains rather more caffeine when prepared from strongly roasted than from slightly roasted coffee, because the caffeine is more easily extracted from the former. (Herman Aubert. See A. J. P., 1873, 121.) Paul and Cownley found in preparing "low and medium roasted" coffee no perceptible loss of alkaloid, while in "over-roasted" coffee the loss amounted to one-third. The average of caffeine in roasted coffee they fix at 1.3 per cent. (P. J., 1887, 822.) Seissir has devised a method for removing the caffeine from coffee. About 5 kilos of unroasted coffee berries are placed in a closed centrifugal drum which is surrounded by a hot-water jacket. After the addition of about 15 kilos of ethyl acetate, the drum is set in motion, so that the solvent and berries are thoroughly mixed, the temperature being maintained at 68° C. (154.4° F,). At the end of three hours the solvent is drawn off, and replaced by a further quantity of about 10 kilos, and the mixing and extraction are continued for a further two hours. The ethyl acetate is then run off, the berries are heated to 100° 0. (212° F.) to remove the last traces of solvent, and finally dried at 40° to 46° C. (104°-114.9° F), the drum being rotated meanwhile. The ethyl acetate may be recovered by distillation, and the caffeine separated from the residue. The method is the subject of a French patent. (Journ. Soc. Chem. Ind., 1909, 622.)
The leaves of the coffee plant possess properties analogous to those of the fruit, and are extensively used by the Malays. Stenhouse found them to contain caffeine in larger proportion than the coffee bean, and also caffeic acid. The leaves are prepared for use by drying over a clear fire and then powdering by rubbing in the hands. The powder is made into an infusion like common tea. The taste is like that of tea and coffee combined. (P. J., xii, 443; xiii, 207 and 382, and xvi, 1067.)
The effects of coffee are due chiefly, if not solely, to the caffeine which it contains. Some writers, however, believe that the volatile oil, caffeol (caffeone) possesses stimulating properties. The evidence of this point, however, is so contradictory as to render conclusions impossible. (See Reichert, M. News, 1890, lvi; Erdmann, A. E. P. P., 1902, xlviii; Geiser, A. E. P. P., liii, p. 112.)
As a medicine coffee has been almost entirely replaced by the alkaloid caffeine. The infusion is, however, sometimes administered by rectal injection in cases of narcotic poisoning. The disturbances of digestion which follow excessive coffee drinking are not considered by J. Burmann to be due to caffeine, but to a volatile toxic substance formed during roasting and only partly volatilized, named cafeotoxin, which can be eliminated by subjecting roasted coffee to successive treatments with steam under pressure of several atmospheres (J. P. C., 1913, 8, 281.)
Syrup of coffee of the N. F. III was prepared by pouring 500 mils [or 16 fluidounces] of boiling water upon 250 Gm. [or 8 oz. troy] of roasted coffee, in moderately coarse powder, covering and boiling for five minutes, then straining and adding water through the strainer to make 500 mils [or 1 pint]. Then 800 Gm. [or 24 oz. troy] of sugar is dissolved in the strained liquid, by agitation without heat, and enough water added to make 1000 mils [or 2 pints]. Two tablespoonfuls of this syrup may be added to a cup of hot water or milk. It is also used with carbonic acid water.