Phenolics: Tannins, color pigments and flavor compounds originating in the skins, seeds and stems of grapes. Phenolics, which are antioxidants, are more prevalent in red wines than in whites.
Polyphenolic Ripeness: Also known as physiological ripeness, is the concentration of polyphenols in grape skins, seeds and stems, in contrast to the traditional form of measuring ripeness based on sugar content (Brix, Baumé, Oechsle). It has become a trend among vintners to rely more on polyphenolic ripeness than on sugar levels in recent years, as polyphenols are the source of wine's color, flavor and mouthfeel. As grapes mature, particularly in warmer climates, sugar levels frequently rise faster than polyphenol concentrations. Leaving grapes on the vine longer to achieve polyphenolic ripeness has led to an increase in alcohol levels due to higher sugar contents, particularly in California.
Polyphenol: Chemical compounds found in plant life. In grapes, polyphenols are responsible for skin pigment, tannins and flavors—all of which fall under the category of flavonoids—as well as resveratrol, the compound associated with many of wine's health benefits, and which falls under the much smaller polyphenol category of non-flavonoids. Pertaining to wine, grape skins, seeds and stems contain the highest concentrations of polyphenols.
Physiological Ripeness: See Polyphenolic Ripeness.