262 The Fermentation of Cacao 



case the brown colouration does not occur. If 

 the paste of stewed or boiled (gekochteti) 

 beans mixed with the extract of fresh beans 

 be placed in tubes having- a small surface, 

 the browning commences at the surface, and 

 gradually passes to the deeper parts as the air 

 gains access. 



If the beans be boiled (kocht) in water the 

 tannic substances go into solution. This solu- 



o 



tion also turns brown, owing to oxidation, if 

 a small quantity of the above-mentioned 

 extract be added to it. A purified solution of 

 tannin (precipitation with lead acetate, filtering, 

 breaking up of the lead compound by hydrogen 

 sulphide) also turns brown if the extract of 

 fresh beans be added, the colouration commenc- 

 ing on the surface. All these facts force one 

 to the view that oxidase takes a part in the 

 browning, i.e., by bringing about the oxidation 

 of the tannin in cacao-beans. 1 



About 50 grm. of decorticated beans devital- 

 ized by freezing were broken up and placed 

 in a gas-tight rlask. This was shaken several 

 times, and the gases contained in it were 



o 



examined. The result of the analysis was as 

 follows : 



1 The watery extract of boiled cacao-beans can he 

 used very well on the other hand, to prove the presence 

 of oxidase, a fact probably first pointed out by Gruess. 

 This extract is, for instance, stained deep brown by the 

 addition of Castilloa milk, which contains a powerful 

 oxidase. In place of the watery extract, the alcoholic 

 may also be used, but it must first be deprived of fats. 



