Sparkling wine the production of still wine with some noted divergence. At the vineyard, grapes are harvested early when there is still high acid levels. In areas like Australia, winemakers aim to harvest the grapes at 17 to 20° brix. Unlike still wine production, high sugar levels are not ideal and grapes destined for sparkling wine production may be harvested at higher yields. Care is taken to avoid tannins and other phenolic compounds with many premium producers still choosing to harvest by hand rather than risk mechanical harvesting which may split the berries and encourage maceration between the skins and juice. The
Phenolic content in wine grapes varies depending on the variety with Cabernet Sauvignon, Nebbiolo, Syrah and Tannat being 4 of the most tannic grape varieties. The reaction of tannins and anthocyanins with the phenolic compound catechins creates another class of tannins known as pigmented tannins which influence the color of red wine. Commercial preparations of tannins, known as "enological tannins", made from oak wood, grape seed and skin, plant gall, chestnut, quebracho, gambier and myrobalan fruits, can be added at different stages of the wine production to improve color durability. The tannins derived from oak influence are known as "hydrolysable tannins" being created from