Biology Reference
In-Depth Information
many investigators use the term 'cocoa' to
indicate more than one type of product from
Theobroma cacao
, it is usually necessary
to determine carefully the nature of the start-
ingmaterialused.Forexample,Hammerstone
et al.
(1999) isolated a number of compounds
from 'cocoa' but in their experimental por-
tion indicated that they used fresh seeds in
their study.
The proanthocyanidin content of cocoa
powder is very similar if not identical to
that of cacao liquor. The ratio of flavan 3-ols
to other polyphenols has, however, been
found to be higher in cocoa powder than in
cacao liquor or chocolate (Hammerstone
et al.
, 1999; Natsume
et al.
, 2000).
during fermentation. Higher residual polyphe-
nol oxidase and peroxidase activities may
facilitate a higher oxidation of phenolic
compounds in Criollo seeds during drying.
The content of caffeic acid aspartate in cocoa
seed seems to be determined genetically.
The amount of phenolic substances in cacao
seed is linked to the nutrient supply of the
mother plant. When more nitrogen is
present, the content of caffeic acid aspartate
increases and that of polyphenolic com-
pounds decreases. The elevated content of
amides in plants is a typical result of fertili-
zation with nitrogen.
3.8 Bioavailability of
Proanthocyanidins
3.7 Localization of the
Proanthocyanidins in Cacao Seeds
Many proanthocyanidins are found in cacao
products. Although these compounds are
consumed in reasonably large quantities by
many people (100-200 mg/day), they are
poorly absorbed in the upper intestine and
are not degraded
in vivo
by the human stom-
ach (Rios
et al.
, 2002; Manach
et al.
, 2004).
Some of them react with protein to form
insoluble complexes that are apparently
excreted intact. Others are degraded by
microbial action in the colon. Only catechin,
epicatechin, some dimeric and to a lesser
extent trimeric proanthocyanidins are found
in plasma usually as the glucuronides (Manach
et al.
, 2004). Phenolics are often detoxicated
by methylation, sulfonation or glucuronida-
tion in the small intestine or later in the liver,
facilitating excretion by either the urinary or
biliary paths. Procyanidin B2 has been recov-
ered from urine (Urpi-Sarda
et al.
, 2008).
Proanthocyanidins are poorly absorbed
but are metabolized to a great extent by the
intestinal microbiota into various phenolic
acids (Urpi-Sarda
et al.
, 2008), mainly phe-
nylpropanoic, phenylacetic and benzoic
acid derivatives.
The cotyledon mesophyll of seeds of
Theobroma cacao
and related species contains
mostly polysaccharides and lipid and protein
reserve cells (Martini
et al.
, 2008). The seeds of
Theobroma cacao, Theobroma subincanum
and
Theobroma grandiflorum
are more than
50% lipids; the lipid globules gradually accu-
mulate adjacent to the cell wall. The protein
reserves of mature cells of
T. cacao
are densely
scattered among the lipid bodies along with
occasional scattered starch granules. Polyphe-
nolic cells are scattered throughout the meso-
phyll, but also aligned with the respective
vascular bundles. A peculiarity of mature seeds
of
T. cacao
is the presence of rows of polyphe-
nolic cells displayed perpendicular to the coty-
ledon mesophyll edge (Martini
et al
., 2008)
and in lines near the epidermis (Martini
et al.
,
2008; Elwers
et al.
, 2009).
The reduced content of polyphenols in
Criollo cocoa is caused by faster decrease in
amount of the compounds during seed
processing in contrast to other cocoa types
and sub-groups (Elwers
et al.
, 2009). This
decrease may be responsible for the mild
flavour of Criollo type products. Charac-
teristics of the Criollo seed shell or cotyle-
don tissue may permit a faster invasion of
pulp degradation products into the seed and
to a stronger leakage of phenolic compounds
3.9
Important Health Benefits
Although proanthocyanidins are important
for their organoleptic properties (mainly
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