acid and additionally transforms ethanol into acetic
acid. There is an overlapping microbial sequence
involved that is dominated initially by yeasts; this is
followed by lactic acid and acetic acid bacteria [ 4, 5].
It is during this latter phase that the formation of
chocolate aroma precursors is reported to occur.
A patent by Mars Incorporated provided methods
for processing cocoa beans without the requirement
of microbial fermentation. Beans were treated, with
or without adhering pulp, to a solution of ethanol/
water of a volume sufficient to cover the mass, while
maintaining the solution at set temperatures and
times [ 6].
The range of operating conditions reported in this
• Ethanol concentrations in the range of 7-16% v/v
optimally containing up to 12mg of citric acid or
1-5mg acetic acid per g of ethanol solution. These
conditions were such that microbial fermentation
• The beans, generally free from pulp, were incubated intact or following mechanical damage
by cutting, exposure to freeze/thaw or treated to
• Incubations were carried under vacuum, or pressure, at 45o-51oC from 24-96 hours.
It would appear that ethanol and perhaps the
acidic environment, provided by acetic or citric
acid, has a part to play in this substitute process to
classical fermentation. It seems that the activity of
microorganisms in the classical fermentation process
serves only for the anaerobic production of ethanol.
Ethanol may additionally participate in ester
formation or other reactions that contributes to the
subsequent flavor generation step during roasting.
Ethanol at the concentrations employed is reported
to inhibit fermentation. It is known that ethanol
also perturbs the permeability of phospholipid
bilayer double membrane of cells and organelles.
In the cocoa bean, this probably facilitates loss of
compartmentation and cellular integrity resulting in
extensive hydrolytic activity [ 7]. Cellular integrity is
additionally compromised by mechanical disruption
or freeze /thaw treatment.
Lima et al (2011) reported that in the fermenting
cocoa bean, the loss of membrane integrity resulted
in a cascade of reactions leading to the formation
of cocoa flavor precursors. The principal precursors
included reducing sugars, amino acids and peptides.
The enzymes involved in these transformations
include invertase, aspartic endoprotease and carboxypeptidase, respectively. Invertase present in the
shell and cotyledons converts sucrose to the reducing
sugars glucose and fructose [ 9].
In vitro studies by Voigt et al (1994) using the
above proteolytic enzymes, showed that peptides
and hydrophobic amino acids produced by enzymatic hydrolysis were correlated with the formation
of cocoa aroma and that these precursors were
themselves derived from vicilin-like globular
proteins. The products from the amino acids/
peptides and reducing sugars reacted during roasting, mainly by Maillard and Strecker degradation
reactions, have formed key Strecker aldehydes and
pyrazines [ 11].
At the end of the ethanol incubation period, beans
were dried, winnowed, roasted and milled in the
traditional way to produce good quality—in terms of
final product flavor—cocoa powder and cocoa butter.
These products were comparable in flavor quality
to material generated by traditional fermentation
When the traditional fermentation process was
employed, the wet mass of beans were dried either
by spreading in the sun on mats or by using special
drying equipment. Slow drying reduced the moisture
content in the bean from around 60% to about 7%.
It appears that the drying stage also contributes to
the formation of flavor precursors. Dried beans were
packed into sacks for transportation prior to further
This is the process whereby the dried beans are
cracked and a stream of air is used to separate the
shell from the nib; these latter small pieces, rich in
triglycerides, are used to make chocolate. The winnowing process may take place either before or after
roasting depending on the end use of the beans.a
The final flavor of the
cocoa bean will depend
on the genotype, growing
conditions, the bean
maturity and processing
a (http:// www.chocolatiers.co.uk/blogs/guides/7164810-what-are-cocoa-nibs-and-