The Last Word 261 
discolouration, and the cause of this change in 
colour is brought about by the oxidation of the 
tannic substances (possibly preceded by a split- 
ting up of glucosides). 
It has often been.suggested that oxidases 
may play a part in the preparation of cacao. 
Indeed, it is easy to prove that such is the 
case. The oxidation of the tannin in other 
fruits containing that substance is also put 
down to oxidase. If fresh, decorticated cacao- 
beans are crushed in water, the watery extract 
gives a blue colour reaction with tincture of 
guaiacol, and a dark blue reaction with an 
aqueous solution of tetramethyl-paraphenylen- 
diamin hydrochloride. These reactions are 
best obtained by the capillary method of 
J. Gruess.’ 
The oxidase action may be demonstrated 
without the aid of foreign chemical substances. 
If cacao-beans be: heated in water to 75° C. 
and then crushed, no change in colour and no 
reduction of the bitter taste is produced in the 
mass, whilst brown discolouration still occurs 
after heating at 7o* C. for an hour. The 
browning of the beans heated to 70° C. can 
still be obtained if a small amount of aqueous 
extract of fresh cacao-beans be stirred-into the 
mass. For comparison, another portion of 
the mass may be treated with a similar extract 
previously heated to 80° to 100° C.; in this 
1 *¢ Bericht der deutschen botanischen Gesellschaft,” 
Bd. xxvi, p. 624. 
