Scientific research

Excerpt from chapter 8.5 Cocoa
8.5.1 Fermentation
Acetic acid "then permeates the bean, lowering the internal pH to ~4.5 [...] when the death of the seed occurs the cells lose their structural integrity and with it the cell membranes lose their semi-permeability. The phenolic and purine metabolites are then able to slowly diffuse away from their sites of storage within the cell (often first noticed as the diffusion of pigments) [...] (i) Sucrose is converted to glucose and fructose by invertase [...] (ii) Polyphenol-oxidase converts the various phenolic metabolites [...]

8.5.2 Drying
[...] forced hot air drying may cause the shell of the bean to lose moisture preferentially. As a result the shells harden before all the water is lost and thereby the diffusion and loss of volatile acids from the beans is inhibited [...]

8.5.3 Roasting
Fermented beans "possess many of the flavour volatiles - such as alcohols and esters - but their aroma is not usually chocolate-like. [...] Almost all the reducing sugars and at least half of the amino acid content (either as free amino acids or small peptides) are lost in this roasting phase. [...]

'Good' cocoa liquors are not generally derived from cacao beans which possess too high a polyphenol content [...] Polyphenol-enzyme complexation invariably leads to a substantial decrease and eventually loss of enzymatic activity. It is therefore reasonable to suppose that at this point the rates of degradation of storage proteins and sucrose will steadily decrease [...] Depending on the availability of oxygen, the polyphenols themselves [will be] oxidised to quinones which will either form covalent bonds with the proteins (quinone tanning) or self-polymerise. With cacao beans which are rich in polyphenolic metabolites, these [enzymatic] reactions, essential to the devlopment of 'good'cocoa liquors, will therefore be arrested prematurely."