Bitterness and astringency of flavan-3-ol monomers, dimers and trimers

Intensity of astringency and bitterness of seven flavonoid compounds was ev aluated by a time-intensity (TI) procedure. Eighteen trained judges rated i ntensity continuously from ingestion, through expectoration at 10 s until e xtinction of the sensation. The seven stimuli included two flavan-3-ol mono mers, (+)-catechin and (-)-epicatechin, three dimers and two trimers synthe sised from catechin or epicatechin by condensation with (+)-dihydroquerciti n. As the degree of polymerisation increased, maximum bitterness intensity (I-max) and total duration (T-tot) decreased whereas astringency I-max incr eased. The monomers were significantly higher in bitterness at I-max than t he dimers, which were significantly higher than the trimers. Astringency I- max of the monomers was lower than the dimers or trimers, although no signi ficant difference was found in T-tot among the polymer classes. The bond li nking the monomeric units had an influence on both sensory properties. The catechin-catechin dimer linked by a 4 --> 6 bond was more bitter than both catechin-(4 --> 8)-catechin and catechin-(4 --> 8) -epicatechin, Astringenc y was affected by both the specific linkage and the identity of the monomer ic units with the dimer, catechin-(4 --> 8) -catechin, being lower in astri ngency than either catechin-(4 --> 6)-catechin or catechin-(4 --> 8)-epicat echin. (C) 1999 Society of Chemical Industry.