Acetic Acid
Acetic acid is the chemical name for the major component of vinegar. Acetic acid is produced in wine from alcohol by acetic acid bacteria in the presence of air. Acetic acid is the major volatile acid that occurs in foods, and its presence is usually considered to be evidence of bacterial spoilage. The taste and flavor is quite fruity and, to be fair, it must be admitted that small amounts of acetic acid and its esters are natural flavor components of a great many fruits and fruit juices. (Wine,Beer,Spirits,Sake,Mead/Chemistry & Flaws Tasting Terms)