purples
" _consistence_ Leather to cheese Crisp
" _appearance_ Solid Open-grained
" _taste_ More or less bitter Less astringent
or astringent

Whilst several effects of fermentation have not been satisfactorily
accounted for, I think all are agreed that to obtain one of the chief
effects of fermentation, namely the brown colour, oxidation is
necessary. All recognise that for this oxidation the presence of three
substances is essential:

(1) The tannin to be oxidised.

(2) Oxygen.

(3) An enzyme which encourages the oxidation.

All these occur in the cacao bean as it comes from the pod, but why
oxidation occurs so much better in a fermented bean than in a bean which
is simply dried is not very clear. If you cut an apple it goes brown
owing to the action of oxygen absorbed from the air, but as long as the
apple is uncut and unbruised it remains white. If you take a cacao bean
from the pod and cut it, the exposed surface goes brown, but if you
ferment the bean the whole of it gradually goes brown without being cut.
My observations lead me to believe that the bean does not become
oxidised until it is killed, that is, until it is no longer capable of
germination. It can be killed by raising the temperature, by
fermentation or otherwise, or as Dr. Fickendey has shown, by cooling to
almost freezing temperatures. It may be that killing the bean makes its
skin and cell walls more permeable to oxygen, but my theory is that when
the bean is killed disintegration or weakening of the cell walls, etc.,
occurs, and, as a result, the enzyme and tannin, _hitherto separate_,
become mixed, and hence able actively to absorb oxygen. The action of
oxygen on the tannin also accounts for the loss of astringency on
fermentation, and it may be well to point out that fermentation
increases the internal surface of the bean exposed to air and oxygen.
The bean, during fermentation, actually sucks in liquid from the
surrounding pulp and becomes plumper and fuller. On drying, however, the
skin, which has been expanded to its utmost, wrinkles up as the interior
contracts and no longer fits tightly to the bean, and the cotyledons
having been thrust apart by the liquid, no longer hold together so
closely. This accounts for the open appearance of a fermented bean. As
on drying large interspaces are produced, these