Astringency and bitterness of selected phenolics in wine

Trained judges rated intensities of astringency and bitterness of four phenolic substances in white wine by scalar and time-intensity methods. According to scalar rating, astringency, and bitterness increased as a linear function of concentration for catechin, gallic acid, grape seed tannin and tannic acid. The polymeric tannic acid and grape seed tannin were rated more astringent than bitter: the reverse was found for their respective monomers, gallic acid and catechin. Similar results were obtained for maximum intensity ratings by time-intensity methods. As maximum intensity of astringency or bitterness increased directly with concentration, the total duration of aftertaste increased: however, little or no changes in time to maximum were observed. A slightly longer time to maximum perception for bitterness was observed than for astringency.