Phenolic content in wine - quercetin. Like other flavonoids, the concentration of flavonols in the grape berries increases as they are exposed to sunlight. Some viticulturalists will use measurement of flavonols such as quercetin as an indication of a vineyard's sun exposure and the effectiveness of canopy management techniques. Anthocyanins are phenolic compounds found throughout the plant kingdom, being frequently responsible for the blue to red colors found in flowers, fruits and leaves. In wine grapes, they develop during the stage of "veraison" when the skin of red wine grapes changes color from green to red to black. As the sugars in the grape
Seibel grapes or two of Albert Seibel’s grapes together and name their creations after themselves, e.g., Seyve-Villard 5276 (“Seyval Blanc”). Seibel grapes Seibel grapes are a group of wine grape varieties which originated with the work of Albert Seibel crossing European grape with American grape species to increase disease resistance. They were planted widely in France during the 1950s but have seen decline in recent years because French wine law proscribes hybrid grapes in appellation wine. The grapes are still commonly used as blending grapes in table wine and mass commercial wines. New Zealand, England, and Canada also have plantings of Seibel