Physical and chemical constants for the fat of the cocoa bean.

1 Rep. f. anal., Chem., 4,165; Zeitsch. f. anal. Chan.,24, 628. 2 Benedikt, Analyse der Fette und Wachsarten. 3 Prescott, Organic Analysis. 4 Op. cit., note 2, p. 936 of this work.

5 Op. cit.. note 3, p. 936 of this work.

6 Rep. f. anal. Chem., 6,181; Zeitsch. f. anal. Chem., 28, 386.

7 Chem. Zeit. Rep., 13, 309; Chem. Centralbl., 1890,130.

8 Konig, Chemie der menschlichen Nahrungs- und Genussmittel, 3 Aufl., Band I.

For percentages of theobromine in cocoa and cocoa preparations, see tables of analyses given below; for methods of quantitative determination, see methods of analysis given below.

The commercial importance of theobromine at present offers no temptation to remove it from cocoa preparations before placing them on the market.

Small percentages of caffeine have been found in cocoa beans, especially in the shells. It is separated from the theobromine by solution in cold benzol, in which the theobromine is practically insoluble. Weig-mann1 reports 0.17 per cent in cocoa mass and 0.113 to 0.190 per cent in cocoa shells; Bell,2 traces to 0.25 per cent in the bean and 0.33 per cent in the shells.

Nonalkaloidal nitrogenous substances. - Stutzer3 classifies the nitrogenous constituents of cocoa, as follows:

(1) Nonproteids, substances soluble in neutral water solution in presence of Cu(OH)2 (theobromine, ammonia, and amido compounds).

(2) Digestible albumen, insoluble in neutral water solution in presence of Cu(OH)2, but soluble when treated successively with acid gastric juice and alkaline pancreas extract.

(3) Insoluble and indigestible nitrogenous substances.

In the same article he writes as follows in regard to the food value of the nitrogenous constituents of cocoa:

The group of nitrogenous constituents is of great importance in all foods, especially their content of digestible albumen. Among the general public the opinion is very widely extended that cocoa belongs to the very easily digestible foods. The extremely favorable mechanical treatment is certainly such that the digestive fluids have no considerable mechanical resistance to overcome in the assimilation of the nutritive constituents of cocoa. On the contrary, the chemical reaction between the solvent constituents of the digestive juices and the nitrogenous nutritive constituents of cocoa can not be called an especially strong one. A large proportion of these constituents, in spite of apparently favorable conditions, remain entirely indigestible, entirely worthless. I have already called attention to the slight digestibility of the albuminous substances of cocoa,5 and once illustrated their difficult digestibility graphically in the Berliner Hygiene-Ausstellung. In the meantime, these observations have been confirmed by investigations of H. Weigmann, which he undertook on his own account. Weigmann found only 42 per cent of the nitrogenous substances in cocoa to be digestible.

1 Op. cit., note 8, p. 938 of this work.

2 Bell, Analysis and Adulteration of Food.

3 Zeitsch. f. angew. Chem., 1891, 368.

The results of Stutzer's own investigations, referred to above,1 were obtained with three samples of cocoa powder, and are given as follows:

For quantitative data concerning the nitrogenous constituents, see tables on page 960 et seq.

Starch. - Cocoa contains 5.78 per cent to 15.13 per cent of starch. (See tables of analyses.) A more detailed description of this starch will be found in paragraphs devoted to the microscopy of cocoa.

Cocoa red, the coloring matter of the bean, seems to be related to the tannins, but authorities differ as to whether it is a decomposition product of a tannin, or whether a tannin is the result of its decomposition.

It is obtained from the aqueous or alcoholic decoction by precipitation with lead acetate and decomposition of the washed precipitate with hydrogen sulphide. The solution thus prepared has a bitter taste; according to Watts, gives a dark green or brown precipitate with ferric and a green or sometimes violet precipitate with ferrous salts; absorbs oxygen, becoming acid, the coloring matter being converted into a kind of tannic acid, which is precipitated by gelatin - cocoa red in its unaltered state not being thus thrown down (Hassall).2

It is colored blue by iron salts and dissolved out by caustic potash with a green color, by sulphuric acid with a red color, and by acetic acid and alcohol with a violet color. Cold water dissolves the pigment with difficulty, while warm water dissolves it entirely. Since the fresh seeds are colorless, Mitscherhch presumes that cocoa red is formed by a process of oxidation from a body related to the tannins (Moeller).3

It is changed to tannin by oxidation and colored green by iron salts (Tuchen).4

Concerning the astringent principle of cocoa and cocoa red, Thorpe5 writes as follows:

The astringent principle is of the nature of tannin, but is different from the tannin of tea and coffee. It rapidly changes during analysis to cocoa-red, which renders its quantitative estimation difficult. It is precipitated by subacetate of lead and may be obtained from this precipitate by decomposition with hydrogen sulphide; gives a green precipitate with ferric chloride, not unlike that given by caffeic acid under similar treatment (Bell).

1 Rep. f. anal. chem., 1882, 88 and 165; Hygiene-Bericht, 1882-'83,1. 217; also op. cit.. note 8, p. 938 of this work.

2Hassall, Food: its Adulteration and the Methods for their Detection.

3Moeller, Mikroskopie der Nahrungs- und Genussmittel aus dem Pflanzenreiche.

4Tuchen, Dissertation liber d. organ. Bestandtheile der Cacao.

5Thorpe, Dictionary of Applied Chemistry.

Cocoa-red is not present in the fresh beans, but is the product of the oxidation of the natural tannin of the seed. It consequently appears in different quantities in different cocoas. It has the characters of a resin and exhibits variable degrees of solubility, probably coinciding with the extent of oxidation which it has undergone.