Acetic acid bacteria
These will cause the conversion of alcohol to acetic acid (vinegar). The acetic acid formed will also combine with the alcohol remaining in the wine to form ethyl acetate (or ethyl ethanoate), which is very pungent and smells of acetone (nail polish remover). Acetic bacteria are highly aerobic, so to prevent acetic spoilage, it is important to keep contact between the wine and air to the minimum when it is in tank or barrel. Maintaining an adequate level of free sulphur dioxide (20 mg/l) and good winery hygiene is also important.