phenolic compounds [fee-NAHL-ihk]
Naturally occurring compounds present in grape skins and seeds and extracted from oak barrels. phenolic compounds, sometimes called phenols or phenolics, include tannins and pigments and are responsible for astringency, bitterness, color, some flavors and odors (like vanillin), and antioxidant activity (which helps wines age well). These compounds are present in all wine in small amounts, with red wines containing more because of the extended contact with skins and seeds and, in many cases, longer oak barrel aging.
The New Wine Lovers Companion, 2nd Edition, by Ron Herbst and Sharon Tyler Herbst. Copyright © (1) 2003, 1995 by Ron Herbst and Sharon Tyler Herbst. Reprinted by arrangement with Barron's Educational Series, Inc.