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
Wine Grapes viticulture" written by Pierre Viala and Victor Vermorel and published in 1901–1910. Wine Grapes Wine Grapes - A complete guide to 1,368 vine varieties, including their origins and flavours is a reference book about varieties of wine grapes. The book covers all grape varieties that were known to produce commercial quantities of wine at the time of writing, which meant 1,368 of the known 10,000 varieties. It is written by British Masters of Wine Jancis Robinson and Julia Harding in collaboration with Swiss grape geneticist Dr. José Vouillamoz. "Wine Grapes" is not an update of Robinson's earlier book "Vines, Grapes