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
Wine in religious communities of the Middle East drinks such as "tilā’" and "naqir" as inebriating and thus forbade the pressing of grapes and the drinking of pressed grape juice. As the early Muslim armies conquered more territory, though, increasing populations of non-Muslims were brought under Muslim rule, necessitating the development of a body of law regulating the interaction between Muslims and non-Muslim dhimmis. A document used for guiding Muslim pacts with dhimmi communities known as the "Shuruṭ ‘Umar" forbids dhimmis from selling forbidden products – pork, wine, carrion – to Muslims. The Egyptian Jewish communities of the medieval period used wine sacramentally in feasts, prayers, and at