2009_Book_FoodChemistry

21.3 Cocoa and Chocolate 963
77 mg/g epicatechin equivalents (ECE), cocoa
powder contains very high concentrations compared
to, e. g., green (83 mg/g GAE, 24 mg/g
ECE) and black tea (62 mg/g GAE, 17 mg/G
ECE).
Three groups of phenols are present in cocoa: catechins
(about 37%), anthocyanins (about 4%) and
leucoanthocyanins (about 58%).
The main catechin is (−)-epicatechin, besides
(+)-catechin, (+)-gallocatechin and (−)-epigal-locatechin.
The anthocyanin fraction consists
mostly of cyanidin-3-arabinoside and
cyanidin-3-galactoside.
Pro- or leucoanthocyanins are compounds which,
when heated in acidic media, yield anthocyanins
and catechins or epicatechins, respectively. The
form present in the greatest amount is flavan-3-4-
diol (I in Formula 21.9) which, through 4 → 8 (II)
or 4 → 6 (III) linkages, condenses to form dimers,
trimers or higher oligomers (cf. 18.1.2.5.2, Formula
18.20).
Leucoanthocyanins occur in fruits of various
plants in addition to cacao; e. g., apples, pears
and cola (kola) nuts.
21.3.2.3.6 Organic Acids
Of the organic acids (1.2–1.6%), citric, acetic,
succinic and malic acid contribute to the taste of
cocoa (Table 21.23). They are formed during fermentation.
The amount of acetic acid released by
the pulp and partly retained by the bean cotyledons
depends on the duration of fermentation and
on the drying method used. Eight brands of cocoa
were found to contain 1.22–1.64% total acids,
0.79–1.25% volatile acids and 0.19–0.71% acetic
acid.
Table 21.23. Taste substances of roasted cocoa nibs
Compound
Concentration
(mmol/kg)
(21.9)
Bitter Group
cis-cyclo (L-Pro-L-Val) 8.9
Theobromine 63.6
cis-cyclo (L-Val-L-Leu) 0.82
cis-cyclo (L-Ala-L-Ile) 0.64
cis-cyclo (L-Ile-L-Pro) 0.54
Astringent Group
N-[3 ′ ,4 ′ -Dihydroxy-(E)-cinnamoyl]-
3-hydroxy-L-tyrosine 0.9
(−)-Epicatechin 8.6
Quercetin-3-0-β-D-glucopyranoside 0.10
Quercetin-3-0-β-D-galactopyranoside 0.034
γ-Aminobutyric acid 5.0
Sour Group
Citric acid 31
Acetic acid 17
Succinic acid 1.7
Malic acid 3.6