(2) _Colour._ The change in the tannin results in the white (criollo) beans becoming brown and the purple (forastero) beans becoming tinged with brown. The action resembles the browning of a freshly-cut apple, and has been shown to be due to oxygen (activated by an oxidase, a ferment encouraging combination with oxygen) acting on the astringent colourless substance, which, like the photographic developer, pyrogallic acid, becomes brown on oxidation.
(3) _Aroma._ A notable change is that substances are created within the bean, which _on roasting_ produce the fine aromatic odour characteristic of cocoa and chocolate, and which Messrs. Bainbridge and Davies have shown is due to a trace (0.001 per cent.) of an essential oil over half of which consists of linalool.[3]
(4) _Stimulating Effect._ It is commonly stated that during fermentation there is generated theobromine, the alkaloid which gives cacao its stimulating properties, but the estimation of theobromine in fermented and unfermented beans does not support this.
(5) _Consistency._ Fermented beans become crisp on drying. This development may be due to the "tannins" encountering, in their dispersion through the bean, proteins, which are thus converted into bodies which are brittle solids on drying (compare tanning of hides). The "hide" of the bean may be similarly "tanned"--the shell certainly becomes leathery (unless washed)--but a far more probable explanation, in both cases, is that the gummy bodies in bean and shell set hard on drying.
[3] _Journal of the Chemical Society_, 1912.
We see, then, that although fermentation was probably originally followed as the best method of getting rid of the pulp, it has other effects which are entirely good. It enables the planter to produce a drier bean, and one which has, when roasted, a finer flavour, colour, and aroma, than the unfermented. Fermentation is generally considered to produce so many desirable results that M. Perrot's suggestion[4] of removing the pulp by treatment with alkali, and thus avoiding fermentation, has not been enthusiastically received.
Beans which have been dried direct and those which have been fermented may be distinguished as follows:
_Shape of bean_ Flat Plumper _Shell_ Soft and close fitting Crisp and more or less free. _Interior: colour_ Slate-blue or mud-brown Bright browns and purples " _consistence_ Leather to cheese Crisp " _appearance_ Solid Open-grained " _taste_ More or less bitter Less astringent or astringent