The seeds of Theobroma Cacao, Linné.
COMMON NAMES: Cacao, Cocoa (incorrectly), or Chocolate tree.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 38.
Botanical Source.—The genuine cacao tree is a small and handsome evergreen tree, growing in South America and the West Indies, from 12 to 25 feet high, and branching at the top; when cultivated it is not allowed to grow so high. The stem is erect, straight, 4 to 6 feet high; the wood light and white; the bark thin, somewhat smooth, and brownish. The leaves are alternate, petiolate, lanceolate-oblong, ribbed, veined, entire, smooth on both sides, dark-green, 8 to 10 inches long, the younger ones rose-colored; the petioles terete, thinner in the middle, with 2 small, linear, awl-shaped stipules at base. The flowers are very small, clustered, axillary, but emanate from the sides of the stems; they are white, with a reddish tint, and scentless. Pedicels uniflorous and filiform. The calyx consists of 5 sepals, and is deciduous; the divisions are ovally lanceolate, angustate, and pointed. Petals 5, vaulted at the base, ligulate above. Stamens, linear, awl-shaped, urceolate, the 5 sterile ones much longer than the 5 fruitful ones, and alternate with the petals; the 5 fruitful ones opposite the petals, and bearing 2 anthers. The style is 5-cleft at the apex.; the stigmas simple. Ovary free, sessile, oval, elongated, 10-grooved, downy, with 8 ovules in 2 rows in each of the Compartments. Fruit indehiscent, ovate-oblong, 5-celled, and covered with a ligneous, leather-like bark, emanating from the sides of the stems. The seeds are numerous, compressed, 1 inch long, reddish-brown externally, dark-brown internally, and imbedded in a whitish, sweetish, buttery pulp. (On the anatomical structure of cacao seed, see A. Tschirch, Archiv. der Pharm., 1887, p. 605.)
Source, History, and Preparation.—This tree was extensively cultivated in Mexico, Central and South America for many years, indeed long before the discovery of America, and at one time formed the currency of the natives, who made an immense consumption of it in various ways. At present it is chiefly cultivated in Brazil, Costa Rica, Guayaquil, Ecuador, Venezuela, Peru, Guatemala, the. island of Trinidad, and most of the other West India Islands; also in Africa, Ceylon, Samoa, and other parts of the globe. The cocoa or chocolate nuts of commerce are the seed taken from the fruit and deprived of a slimy covering. There are many varieties of this seed brought into the market, named, according to the place from which they have been imported, e. g., Puerto Cabello, Cauca, Maracaibo, Caracas, Surinam, Java, Domingo, Bahia, etc.
Cacao seeds are prepared for commerce either by simple drying, in which case they retain their bitterness and astringency; or they are cured by a sweating process by which their bitter and astringent properties are much modified, and the color of the seed changed. The seeds are placed into closed boxes for a certain length of time, or buried in the ground for a few days; the best process is to allow the seeds to lie for a week in heaps covered with green leaves, such as plantain leaves, etc., after which time they are dried. Also see directions given by W. Cradwick, of Jamaica, for curing cacao seeds on a domestic scale, in Amer. Jour. Pharm., 1895, p. 530.
Description.—The best cacao seeds are large, full and heavy, smooth, of a beautiful, light chestnut-brown color, free of foreign matter, well sieved, dry, not musty, without disagreeable or rancid smell, but of an agreeable odor, and a mild somewhat bitter and fatty taste, with but little astringency. When the kernels are separated from the shell and broken, they should be shining and violet-brown, not traversed by white streaks. It is said that under the most favorable circumstances cacao can not be preserved for more than three years. The cracked cocoa, or cocoa nibs of commerce is coarsely ground cacao previously roasted. Commercial cocoa may also consist of the powdered press-cake obtained when the oil or butter of cacao is partially removed by pressure. Chocolate is prepared by first roasting the seed, then removing their husks as soon as the requisite degree of aroma and of friability is obtained, allowed to cool, and cracked or ground between heated stones, which causes them to assume the consistence of paste, which is molded into rectangular cakes. When roasted cacao seeds are ground with about an equal amount of sugar and certain aromatics, the product constitutes sweet chocolate. Those who manufacture chocolate have various methods of preparing, sweetening, and aromatizing it. Cacao shells are also an article of commerce, being used in preparing a table beverage resembling chocolate or cocoa in taste, but being naturally weaker than these.
Chemical Composition.—Cacao seeds contain fat (40 to 50 per cent) (oil of cacao, cacao butter; see Oleum Theobromatis), the base theobromine (C7H8N4O2), small quantities of caffeine (theine), starch (from 1.3 to 7.5 per cent, Ridenour, Amer. Jour. Pharm., 1895, p. 209), a red coloring matter (cacao-red), albuminous matter (6 to 18 per cent), and ash (2 to 4 per cent), etc.
In 18 commercial specimens of cacao, A. Eminger (Forschungsberichte über Lebensmittel, 1896, p. 275; also see Amer. Jour. Pharm., 1897, p. 113) found theobromine to vary from 0.88 to 2.34 per cent, caffeine from 0.05 to 0.36 per cent. According to E. Knebel (1892), the presence of cacao-red is due to the decomposition of a glucosid under the influence of a diastatic ferment, resulting in dextrose, cacao-red. theobromine. and caffeine (compare Kola).
THEOBROMlNE was discovered in cacao seeds by Woskresensky in 1841. It is also a constituent of Kola nuts (see Kola). It crystallizes in small rhombic needles, has a bitter taste and sublimes without decomposition at about 290° C. (554° F.). Its solubilities, as revised by Eminger (loc. cit.), are as follows: It requires 736.5 parts of water at 18° C. (64.4° F.), 136 parts at boiling temperature, 5399 parts of alcohol (90 per cent) at 18° C. (64.4° F.), 440 parts at boiling heat, and 818 parts of absolute alcohol at the boiling point; 21,000 parts of ether at 17° C. (62.6° F.); 4856 parts of methyl alcohol at 18° C. (64.4° F.); 5808 parts of chloroform at 18° C. (64.4° F.), and 2710 parts at the boiling point. It is insoluble in carbon tetrachloride (CCl4) at 18° C. (64.4° F.), while caffeine at this temperature is soluble at the ratio of 1:1000. The author bases upon this a method of quantitative separation of caffeine from theobromine, which was before possible only by precipitating theobromine by means of nitrate of silver in ammoniated solution (compare W. Kunze, Amer. Jour. Pharm., 1899, 145). Theobromine is insoluble in petroleum-ether. Its aqueous solution is neutral, but it forms crystallizable salts with acids. Chemically it is dimethylxanthin (E. Fischer, 1882). A. Eminger assays cacao for theobromine by extracting the fat with petroleum-ether, boiling the residue with a 3 to 4 per cent sulphuric acid to produce the insoluble cacao-red (theobromine is not affected), neutralizing the residue with barium hydroxide, evaporating to dryness with sand, extracting theobromine and caffeine with chloroform, and separating both by means of carbon tetrachloride in the cold. This process avoids warming with bases which more or less destroy theobromine. (On the analysis of 12 commercial samples of prepared cocoa, see Florence Yaple, in Amer. Jour. Pharm., 1895, p. 318.)
Cacao shells were found by T. S. Clarkson (Amer. Jour. Pharm., 1887, p. 277) to contain 0.9 per cent alkaloid, 10.9 per cent nitrogenous matter, 5.32 per cent of fat, a resin soluble in ether and alcohol, and having the odor of cacao, 5.6 per cent of mucilage, and 9.07 per cent of ash, containing aluminum.
Action, Medical Uses, and Dosage.—CHOCOLATE, when scraped into a coarse powder, and boiled in milk, or milk and water, is much used as an occasional substitute for coffee, and for a drink at meals. It is a very useful nutritive article of diet for invalids, persons convalescing from acute diseases, and others with whom its oily constituent does not disagree, as is apt to be the case with dyspeptics.
BUTTER OF CACAO is a bland article, rather agreeable to the taste, and highly nutritious; it has been used as a substitute for, or an alternate with, cod-liver oil, and as an article of diet during the last days of pregnancy. It has also been employed in the formation of suppositories and pessaries, for rectal, vaginal, and other difficulties (see Suppositories). It likewise enters into preparations for rough or chafed skin, chapped lips, sore nipples, various cosmetics, pomatums, and fancy soaps; and has also been used for coating pills.
Theobromine when absorbed acts powerfully as a diuretic, and has a stimulant or exciting action which is not possessed by chocolate itself. It is, however, quite difficult of absorption, and is without effect upon the heart and circulation. It enters into the compound known as Diuretin, which, in certain conditions, is an active diuretic.