Sensory-guided decomposition of roasted cocoa nibs (Theobroma cacao) and structure determination of taste-active polyphenols.
Sequential application of solvent extraction, gel permeation chromatography, and RP-HPLC in combination with taste dilution analyses, followed by LC-MS and 1D/2D-NMR experiments and thiolytic degradation, revealed that, besides theobromine and caffeine, the flavan-3-ols epicatechin, catechin, procyanidin B-2, procyanidin B-5, procyanidin C-1, [epicatechin-(4beta-->8)](3)-epicatechin, and [epicatechin-(4beta-->8)](4)-epicatechin were among the key compounds contributing to the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a series of quercetin, naringenin, luteolin, and apigenin glycopyranosides as well as a family of not previously identified amino acid amides, namely, (+)-N-[4'-hydroxy-(E)-cinnamoyl]-L-aspartic acid, (+)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-aspartic acid, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine, (+)-N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-aspartic acid, and (+)-N-(E)-cinnamoyl-L-aspartic acid, have been identified as key astringent compounds of roasted cocoa. Furthermore, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine (clovamide), (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-tyrosine (deoxyclovamide), and (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-tyrosine, reported previously as antioxidants, have been found as contributors of cocoa's astringent taste. By means of the half-tongue test, the taste thresholds of flavan-3-ols and glycosides have been determined.
Stark
Timo
T
Deutsche Forschungsanstalt für Lebensmittelchemie, Garching.
Bareuther
Sabine
S
Hofmann
Thomas
T
D000328:Adult; D002099:Cacao / Q000737:chemistry*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005419:Flavonoids / Q000032:analysis* / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D015394:Molecular Structure; D009812:Odorants / Q000032:analysis; D010636:Phenols / Q000032:analysis* / Q000737:chemistry; D059808:Polyphenols; D012639:Seeds / Q000737:chemistry*; D013649:Taste
D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols