In some countries, grape juice is converted into wine vinegar through a double fermentation—a yeast fermentation of the sugar into alcohol followed by a bacterial fermentation of the alcohol into acetic acid. Balsamic vinegar is a specialty wine vinegar made from grape must, the pulp of grapes that remains after pressing. The sugars in the must are converted into alcohol using naturally occurring yeasts, and the alcohol is subsequently converted into acetic acid using naturally occurring bacteria.