Acids in wine ripened grapes. While concentration varies among grape varieties, it is usually found in higher levels with red wine grapes. The acid is created as a byproduct of the metabolization of nitrogen by yeast cells during fermentation. The combination of succinic acid with one molecule of ethanol will create the ester mono-ethyl succinate responsible for a mild, fruit aroma in wines. Acidity is highest in wine grapes just before the start of "veraison", which ushers in the ripening period of the annual cycle of grape vines. As the grapes ripen, their sugar levels increase and their acidity levels decrease. Through the
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