Evaluation of bitterness and astringency of (+)-catechin and (-)-epicatechin in red wine and in model solution

Two stereoisomeric phenolic compounds, (+)-catechin and (-)-epicatechin, were rated for perceived intensity of oral astringency and bitterness by trained judges using the scalar method. Mouth drying and mouth roughening were also assessed, since they are often associated with astringency. Amounts of 375, 750 and 1500 mg/L of each compound were tasted in red wine, and in a model system, similar in composition to a dry table wine. Preliminary tests showed that these: concentrations were above the threshold level but within the range found in wine. A control sample (model solution or wine without the addition of the above phenolic compounds) was also evaluated. The results showed that the two compounds were both bitter and astringent. The high (-)-epicatechin concentration was significantly more bitter and astringent than the equal concentration of (+)-catechin in the model solution. Mouth drying and roughening ratings showed a similar increasing pattern with the ratings of astringency particularly at the higher concentrations. However, these attributes were rated differently from astringency suggesting that although they contribute to astringency, they are not subsumed by it.