Oral sensations associated with the flavan-3-ols (+)-catechin and (-)-epicatechin

In order to determine and classify the oral sensations associated with the monomeric flavan-3-ols (+)-catechin and (-)-epicatechin, a multidimensional similarity scaling (MDS) study was performed. The flavan-3-ols have been reported as being perceptual astringents, although their molecular weight is too low for them to be classified in the family of astringent plant tannins. The perceptual similarity map of catechin, epicatechin, citric acid, caffeine, gallic, acid, tannic acid, grape-seed tannin (GST), ethanol, aluminum potassium sulfate (alum) and capsaicin was obtained using a complete pair-wise comparison paradigm. The groupings obtained were corroborated using average-linkage cluster analysis (CA). The MDS similarity maps and the CA dendrograms revealed a differentiation of the monomeric flavan-3-ols from the "traditional" astringent compounds tannic acid, GST, and alum. Catechin and epicatechin preferentially grouped with the bitter compounds (caffeine and ethanol), as opposed to the astringent compounds (GST, tannic acid and alum), although subsequent analysis of variance of the similarity scores indicated that the distances were not statistically significantly different. Regardless, while the multidimensional scaling results do not disprove oral sensations other than taste being associated with the monomeric flavan-3-ols, the similarity neighborhoods, the order and pattern of clustering, and the nature of flavan-3-ol chemical interactions all strongly suggest that the sensations elicited by these compounds are not perceptually equivalent to the "astringent" oral sensations evoked by tannic acid, GST, and alum. Rather, the current categorization of flavan-3-ol oral sensation as "astringent" indicates that a refinement of the language used to describe oral sensations is necessitated. (C) 1999 Elsevier Science Ltd. All rights reserved.