An unpleasant flavor typical of oil obtained from olives that have been piled up (or improperly stored before undergoing the extraction process) and have suffered an advanced degree of anaerobic fermentation.

Slightly bitter on the nose, with a pungent odor, confirmed on the palate.

The advanced degree of fermentation produces a variety of compounds, such as octane, ethyl butanoate, butanoic acid, propanoic acid, 3-methyl-1-butanol and other, from which the unpleasant flavor derives.

Fustiness is one of the most common defects in oils, but it is not so simple to identify, because we are unaccustomed to recognizing it.