Louis Pasteur discovers the bacterium responsible for fermentation. He finds that air should be kept from fermenting wine, but is necessary for the production of vinegar. In the presence of oxygen, yeasts and bacteria break down alcohol into acetic acid, the chemical name for vinegar. Until then it was not known that vinegar resulted from exposing wine to air and it was believed to be a chemical process. Today Maille makes its vinegars in Burgundy and stores its aged vinegars in oak vats for one year.