Effect of pH, ethanol and acidity on astringency and bitterness of grape seed tannin oligomers in model wine solution

Astringency and bitterness in red wines are generally considered to be elicited by phenolic compounds and especially by tannins. This study explored the effects of pH, ethanol level and tartaric acid concentration in modifying astringency and bitterness of oligomeric tannins in model wine solutions. Bitterness and overall astringency intensities were successively rated by 16 judges. As ethanol level and pH values increased, the astringency perception was lowered. While pH affected only astringency, ethanol contributed also to the perceived bitterness of tannin oligomers, especially at typical wine ethanol levels (11–15%). The variation of tartaric acid concentration at constant pH did not have any effect on either of these sensory properties.