Definition - What does Phenols mean?
Phenols are responsible for the red color in red wine. It is an organic compound released by plants and animals as a part of their defense mechanisms with a central cyclic benzene ring and varying number of hydroxyl groups as substituents. So, the more stressed the vines are, the more phenols they will produced. Phenols not only affect the color in red wines, but also act as preservatives and affect the taste of wine. Phenols used in winemaking are subdivided into two different groups: non-flavanoids and flavanoids.
WineFrog explains Phenols
Almost all the phenols used in winemaking are derived from grape stems, skins and seeds, with the majority of phenols being extracted from grape seeds. Some phenols are also derived during the fermentation and aging process, although they are low in number in comparison to the amount of phenols naturally present.
Phenols, often referred to as polyphenols or phenolics, are compounds that include natural color pigments like the anthocyanins, tannins, and different flavor compounds. Phenols affect the color, the taste and the aging process of a wine. Mostly existing in the form of tannins, phenol molecules help to preserve wine because they have the ability to absorb oxygen that would otherwise have a bad effect on the wine. Phenols react with oxygen, and this oxidation can be clearly seen when a wine turns brown.
Phenol concentrations of a particular variety can be changed and manipulated by different methods and the manipulation can completely change the flavor and quality of the produced wine. Red wines are rich in phenol from the skin and seed of the grapes, whereas white wines are rich in the phenol from the pulp of their grapes. Tannins, the most common and important variety of phenols, are responsible for the aging potential and the structure of wine. Tannins also react with anthocyanins to provide color stability in wine.