Vinegar is a combination of acetic acid and water made by a two-step fermentation process. First, yeast feed on the sugar or starch of any liquid from a plant food such as fruits, whole grains, potatoes, or rice. This liquid ferments into alcohol. The alcohol is then exposed to oxygen and the acetic acid bacteria Acetobacter to ferment again over weeks or months, forming vinegar. Vinegar typically contains from 5% to 8% acetic acid by volume. The U.S. Food and Drug Administration requires vinegar to contain at least 4% acetic acid, but may range up to 8% in commonly used vinegars. Although acetic acid is responsible for the tart and pungent flavors and odors we recognize, vinegar also contains trace vitamins, mineral salts, amino acids, and polyphenolic compounds. Flavors range from sour to savory to sweet. Some vinegars, such as balsamic, can be left to ferment up to 25 years. Vinegar can be made from anything with sugar, which is why there are so many different varieties of vinegar in the market. The most popular one is by far apple cider vinegar, which has become an almost cult item in our society.