Acids in wine responsible for the sour taste of vinegar. During fermentation, activity by yeast cells naturally produces a small amount of acetic acid. If the wine is exposed to oxygen, "Acetobacter" bacteria will convert the ethanol into acetic acid. This process is known as the “acetification” of wine and is the primary process behind wine degradation into vinegar. An excessive amount of acetic acid is also considered a wine fault. A taster's sensitivity to acetic acid will vary, but most people can detect excessive amounts at around 600 mg/l. Ascorbic acid, also known as vitamin C, is found in young wine grapes
Straw wine of bottles of Refrontolo passito, a Denominazione of Colli di Conegliano DOCG, are produced. This wine is made from Marzemino grapes, it was already appreciated in the past as documented in the opera "Don Giovanni" of W.A. Mozart, where the protagonist describes it as an excellent wine. Recioto di Soave is the passito white wine from around Verona, made from the Garganega grape used in Soave. The name comes from the word, "recie" that in the native Venetian language means 'ears', a reference to this variety's habit of forming two small clusters of extra-ripe grapes sticking out of the top