206 COCOA 



CHAP. 



the escape of the heat generated. In the fermentation 

 of cocoa the rise of temperature is, as in the vinegar 

 industry, due to the action of the vinegar bacterium, 

 which oxidises the alcohol, formed from the sugar 

 of the pulp, into acetic acid. In this process it is clear 

 that free access of air is necessary, in order to provide 

 sufficient oxygen to oxidise the alcohol. 



The reason for turning over the cocoa daily from 

 one fermenting box to the next one will now be under- 

 stood : its aims are ( 1 ) to mix the heap and to bring 

 those beans which were not in a position to get much 

 oxygen (e.g. in the middle of the heap) into better 

 contact with the air ; and (2) to prevent the temperature 

 rising too high. In the middle of the heap, though the 

 oxidation is there not so very active, the temperature 

 rises all the same, because the heat is not able to escape 

 easily. When the heap is turned over, these parts are 

 cooled and other groups of beans take their place in the 

 middle of the heap. Insufficient aeration of the cocoa 

 during fermenting not only results in slow fermentation 

 but also brings another bacterium into action, the 

 bacterium of butyric acid. This bacterium lives and 

 propagates quickly, when the heap is insufficiently 

 aerated ; it produces butyric acid, the bad smell of 

 which is so characteristic of cocoa which is fermented 

 in a primitive way in unsuitable boxes, as sometimes 

 happens with small proprietors. 



The changes which the pulp undergoes during 

 fermentation are sometimes called external fermenta- 

 tion, while internal fermentation denotes the changes 

 which take place in the seed itself. As we have seen, 

 the external fermentation consists mainly in the de- 

 composition of the sugar of the pulp into alcohol and 

 carbon dioxide, followed closely by the oxidation of the 

 alcohol to acetic acid, which is accompanied by a rise of 

 temperature. This rise of temperature is the cause of 

 the internal fermentation. 



To make this internal fermentation understood, it 

 must be pointed out that no chemical changes of any 



