44 The Fermentation of Cacao 
colour within a short time, while boiled seed 
thus treated will not show any change of colour, 
even after many hours’ exposure to the air. 
This is in full analogy with similar phenomena 
observed very. frequently with plants, and is 
due to the presence’of oxidases or oxidizing 
enzymes. When cells are killed by being cut 
open or in any other way that will not injure 
the oxidases, these will, upon the death of the 
protoplasm in which they are stored up, be 
liberated and at once commence their activity, 
easily recognized by the early appearance of a 
brown, black, or red colour. These colours 
are often due to the oxidation of various 
kinds of tannins originally present in the juice 
or cell sap. If, however, the death of the 
protoplasm is produced by strong acids or 
boiling temperature,’ the oxidases will also be 
killed and no colour change will be noticed, as 
the tannins and other readily oxidizable matters 
in the juices cannot ‘easily take up the 
atmospheric oxygen without the assistance of 
oxidases. 
A further control experiment was made in 
which the pulped cacao (seed with testa and 
attached slime layer) was boiled for about 
twenty minutes with a 2 per cent. dilute sul- 
phuric acid. The slimy tissue contracted, and 
‘ Such a case is observed in the curing of tobacco, 
whereby a fine brown colour is produced. 
2 The killing temperature for oxidases is 20° to 30° C. 
higher than that for protoplasm or living matter. 
