The purest form is the cocoa-nibs. When these are boiled in water, a brownish decoction is formed, with the fat as a scum at the top; this may be removed, and the decoction flavoured with milk and sugar. In this form, cocoa can be taken by invalids with weak digestion, who would be nauseated by the fat of ordinary cocoa or chocolate.
The best cocoa is prepared as above; but the lowest quality contains the husks of the beans, with hardly any of the beans in it; a somewhat better, though still inferior sort, is made from the smaller fragments of the nibs, and a good deal of husk. In some cases the cacao butter is removed during the process of preparation, and starch or sugar substituted. This form is less likely to disagree with dyspeptics than whole cocoa.
The action of the Volatile Oil (not the cacao-butter) developed during roasting, is probably similar to that of tea and coffee, though it is less in amount. The bitterness is greater than that of coffee, but the astringency less than in either tea or coffee.
The Concrete Oil, or fat of cocoa, forms about half its weight. It is white, and not apt to turn rancid, and possesses an agreeable flavour. Cocoa also contains a certain amount of starch and cellulose.
Theobromine is a white crystalline alkaloid, the exact analogue of caffeine. The latter, in fact, is methyl-theobromine—that is, theobromine plus the theoretical group CH₂. Theobromine possesses similar properties to caffeine. It amounts to 1.5 to 2 per cent. of the whole bean. The ordinary preparations of cocoa differ considerably in composition as may be seen from the following table of per centage composition (Ewell). In each instance other nitrogenous and non-nitrogenous constituents go to make up the total 100:
| FAT. | FIBRE. | CANE-SUGAR. | ASH. | ADDED STARCH. | |
|---|---|---|---|---|---|
| Fry’s Cocoa Extract | 30·9 | 3·9 | — | 4·2 | None. |
| Schweitzer’s Cocoatina | 31·1 | 3·7 | — | 6·3 | Do. |
| Rowntree’s Cocoa Extract | 27·6 | 4·4 | — | 8·5 | Do. |
| Van Houten’s Cocoa | 29·8 | 4·4 | — | 8·6 | Do. |
| Epps’s Prepared Cocoa | 25·9 | 1·5 | 26 | 3·1 | Much arrowroot. |
Some of the preparations of cocoa (e.g. Van Houten’s) have added to them alkaline salts to increase their solubility. Cocoa is not such a valuable food as might appear from the large amount of fat in it, because only moderate quantities of this can be taken without deranging digestion. In Vi-Cocoa a certain amount of kola is added, which contains a considerable proportion of caffeine. The addition of such a drug to a beverage is distinctly to be deprecated.
Minor Stimulants.—Beverages containing theine, or some analogous principle, appear to be employed in most countries. In moderate doses, they may assist the assimilation of other foods, but their main influence is on the nervous system. Theine-containing substances may be described as both sedative and exciting. They are sedative, in that they allay nervous irritability, and tend to “take the edge off” the disturbance caused by outward circumstances; and they are exciting, inasmuch as they are known to form an admirable antidote to the stupefying effects of opium or alcohol. The wakefulness from tea is an instance of the same thing, while the allaying of sensations of cold and hunger by a cup of tea is an instance of the sedative effect.
In Brazil, Guarana (from Paullinia sorbilis) is used as a drink; it contains theine, the quantity of which is twice as much as in good black tea, and five times as much as in coffee. Like green tea, a cup of guarana infusion is sometimes extremely valuable in nervous headaches.
In Peru, the natives use the leaves of the Coca plant (Erythroxylon coca), which must be carefully distinguished from cocoa. It is chewed somewhat in the same way as the betel-nut. It contains two alkaloids—cocaine and hygrine, as well as tannin. In its stimulant action it resembles tea and coffee. The active principle of this plant, Cocaine, is a valuable local anæsthetic. Internally it has been taken as a stimulant and restorative. Various wines containing Coca, with vaunted restorative powers, are advertised. They are mischievous when taken frequently. Nature’s remedy for fatigue, whether mental or body, is rest and recreation. Stimulants of this class, even though they enable work to be continued for awhile, eventually increase the exhaustion for which they are taken.