940 



FOODS AND FOOD ADULTERANTS. 



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 stal'ch 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 pro- 

 duct of a tannin, or whether a tannin is the result of its decomposition. 



It is obtained from the aqueous 'or alcoholic decoction by precipita- 

 tion 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 taunic 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, Thorpe 5 

 writes as follows : 



The astringent principle is of the nature of tannin, but is different from the tan- 

 nin of tea and coffee. It rapidly changes during analysis to cocoa-red, which ren- 

 ders its quantitative estimation difficult. It is precipitated by subacetate of lead 

 and may be obtained from this precipitate by decomposition with hydrogen sulphide ; 



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. 



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

 3 Moeller, Mikroskopic dor Nahrnngs- mid Genussinittrl aus dcin I'flau/enreiche. 

 *Tucheu, Dissertation liber d. organ. Bestandthi-ilt' der Cacao. 

 6 Thorpe, Dictionary of Applied Chemistry. 



