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
Straw wine Czech wine law, is classified as a Predicate wine (Czech: "Jakostní víno s přívlastkem"). Czech regulations require the harvested grapes to come from a single wine sub-region, the grapes must be dried for at least three months either on straw or reed mats or hung in a well-ventilated space, and the must weight is required to reach at least 27° NM on the Normalizovaný moštomer scale. Straw wine in the Czech Republic is typically made from white grapes that are well-ripened and undamaged. Vin de Paille is the French for 'straw wine', made only in the ripest vintages. Perhaps the