Czech wine of these festivals in Znojmo, Mikulov, Brno and Mělník will feature samples of hundreds of local wines as well as local music, dancing and cuisine. These wine-festivals take place in big towns apart from the wine-producing areas as well (such as Prague). Czech wine law classifies wine according to the origin of the grapes and the ripeness of the grapes determined by measuring the must weight in the grape juice at the time of harvest. Sugar content is expressed in units of °NM on the Czecho-Slovak Normalised Must-Weight Scale (Czech: "Normalizovaný moštoměr"), which indicates how many kilograms of sugar are
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