AERATION AND FERMENTATION 127 



Coloniale, January 25, 1909) conducted experiments to 

 ascertain whether the fermentation of cocoa is due to a 

 chemical or a biological process. Seven kilos. (15'4 Ib.) 

 of cocoa beans, freshly taken from the fruit-shells, were 

 placed in four different baskets. To one of these was 

 added formaldehyde and to another chloroform. These 

 two substances check the development of the lower 

 organisms, but do not affect chemical reactions. 



The cocoa beans in the two untreated baskets fer- 

 mented in the usual way, but no fermentative changes 

 occurred in the beans treated with formaldehyde and 

 chloroform. Upon formaldehyde and chloroform being 

 respectively added to the two baskets of fermenting beans, 

 the fermentation was stopped and the temperature was 

 reduced. 



In order to prove that the presence of air is essential 

 in cocoa fermentation, four cylinders were taken and 

 4 kilos. (8'8 Ib.) of fresh cocoa beans were placed in each. 

 Arrangements were made for the free ingress of air to 

 two of the cylinders and the other two were hermetically 

 closed. Fermentation took place in the beans in the 

 aerated cylinders, but those in the hermetically closed 

 cylinders rapidly decomposed. When air was withheld 

 from the fermenting beans decomposition rapidly set in. 



The necessity for air in connection with cocoa fer- 

 mentation is well demonstrated in practice. Fermenta- 

 tion changes are always first manifested in the portions 

 of the bean-mass best aerated . \Vhen too large quantities 

 of beans are bulked, the beans in the centre of the 

 mass will often show no signs of fermentative activity, 

 although it may be proceeding satisfactorily in the outer 

 portions of the mass. If no proper provision is made 

 for the escape of the liquid which oozes from the bean- 

 pulp, fermentation is arrested at the bottom of the heap 

 and decomposition soon sets in. 



The carbohydrates in the pulpy envelope of the beans 

 provides nutrition for the development of numerous 

 yeast cells, Saccharomyces spp. These multiply rapidly 

 and convert the sugar into alcohol. Nourishment is also 

 provided for various bacteria, among them the well-known 

 acetic acid bacillus. The pulpy envelope is gradually 

 decomposed by the action of the yeasts, and bacteria 

 and the juice thus formed drain away. The respiration 



