Biology Reference
In-Depth Information
This may be important because cacao liquor
and chocolate are manufactured by fermen-
tation and roasting of cacao beans. In addi-
tion, (−)-catechin has been detected during
roasting of cacao seeds and may also arise
by epimerization during roasting (Kofink
et al
., 2007).
proanthocyanidin oligomers in chocolate
extract is much lower than in extracts of
non-fermented seeds, but ions for proan-
thocyanidins through nonamers were found,
as were ions for procyanidin glycosides.
Quercetin glycosides, theophylline and
other compounds also were encountered
(Hammerstone
et al.
, 1999).
Purification of polar fractions from cacao
liquor extracts gave 17 phenolics including
four new compounds. These new com-
pounds included a
C
-glycosidic flavan, a
O
-glycoside of a dimeric and two
O
-glycosides
of
3.5
Cacao Liquor
Fermented and roasted cacao is the source
of cacao liquor, a major precursor of choco-
late and cocoa. After roasting and winnow-
ing (removing the outer shell from the cacao
beans), the seeds are ground making cacao
liquor. The heat that is generated melts the
cocoa fat generating a liquor. The liquor
hardens to unsweetened chocolate, often
called 'baking chocolate', when it cools
below 35°C. The exact composition of cacao
liquors depends on the cacao variety, post-
harvest processes, such as fermentation and
drying, and roasting conditions (Wollgast
and Anklam, 2000).
Cacao liquors of various sources differ
quantitatively, but mostly have the same com-
ponents, i.e. similar profiles (Redovniković
et al.
, 2009). Polyphenol levels in defatted
cacao liquor are approximately 30-74 mg/g
(Luna
et al.
, 2002), but a comparison of the
amounts of polyphenols present in cacao
products based on the literature is difficult
because of differences in the methods used to
determine this group of compounds. Cacao
liquor consists of approximately 50% fat con-
tent (Luna
et al.
, 2002). Theobromine content
varies from 17 to 26 mg/g of dry weight of the
defatted material (Luna
et al.,
2002). Caffeine
normally occurs at lower levels. Sugars vary
in the range of about 20-25 mg/g in cacao liq-
uor and largely consist of sucrose, fructose
and glucose, in decreasing order.
Although the amount of proanthocyani-
dins in cacao liquor is less than in the origi-
nal seeds, the overall composition seems to
be relatively similar. Mass spectral analysis
of dark chocolate, which is similar to cacao
liquor, in the negative mode revealed the
presence of a complex series of procyani-
din oligomers. The relative abundance of
trimeric
A-linked
proanthocyanidins
(Hatano
et al.
, 2002).
Procyanidin B2, protocatechuic acid,
(+)-catechin, (−)-epicatechin, 3T-
O
-b-D-
galactopyranosyl-
ent
-epicatechin-(2a→7,
4a→8)-epicatechin (T refers to the 'top' moi-
ety of the structure as usually drawn with the
epicatechin unit at the top, and extension
units below), procyanidin C1, procyanidin B5,
cinnamtannin A
2
, 3T-
O
-a-D-Galactopyranosyl-
ent
-epicatechin-(2a→7,4a→8)-epicatechin,
proanthocyanidin A1, proanthocyanidin A2,
bis 8,8′-catechinylmethane and quercetin
3-
O
-a-L-arabinopyranoside were isolated by
extraction from cacao liquor with ethyl acetate
and
n
-BuOH, followed by chromatography
Sephadex LH-20 and Toyopearl HW-40 and
similar resins. A few additional and somewhat
unusual compounds have been reported. The
O
-glycoside of a dimer and two
O
-glycosides
of A-type procyanidins have been isolated
from cacao liquor. However, direct evidence
has been obtained that B-type procyanidin
dimers convert to A-type dimers by oxidative
reactions under mild conditions (Prior and
Gu, 2005) and thermally catalysed reactions
may be responsible for the formation of the
A-type compounds.
3.6
Cocoa Proanthocyanidins
Pressure is applied to the cacao liquor
(while slightly heated) to remove some of
the fat, which is also called cocoa butter.
The remaining cocoa solids usually contain
10-25% cocoa butter. The solids are then
ground to cocoa powder. However, because
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