262 The Fermentation of Cacao 
case the brown colouration does not oécur. If 
the paste of stewed or boiled (gekochten) 
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 (Aoch2) in water the 
tannic substances go into solution. This solu- 
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, z.e., by bringing about the oxidation 
of the tannin in cacao-beans.’ 
About 50 grm.. of decorticated beans devital- 
ized by freezing were broken up and placed 
in a gas-tight flask. This was shaken several 
times, and the gases contained in it were 
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. 
