Q. Does vinegar go bad? If so, how can you tell? Isn't vinegar just wine that's gone bad?
Just as yeast consuming the sugars in grape juice creates alcohol as a by-product, bacteria known as "acetobacteria" consume the alcohol in wine and create acid. This acetic acid is what gives vinegar its characteristic sharp, bright flavors.
Since the acetobacteria live off the alcohol they consume, any number of different alcoholic products can be turned into vinegar. And the type of alcoholic liquid used as the initial ingredient of an alcohol has a pronounced effect on the flavor of the vinegar. That's why red wine vinegar tastes different from champagne vinegar.
Vinegars are often further flavored with additional ingredients such as herbs, or -- like balsamic vinegar -- through aging in wooden barrels.
When purchasing vinegar, keep in mind that you often get what you pay for. Some "cider flavored" vinegars are really just cheap distilled white vinegar to which coloring and additional flavors have been added.
Much of what is sold as balsamic vinegar here is simply red wine vinegar with caramel or caramel coloring added to make it syrupy and sweet like true balsamic.
The surprising news is that vinegar does indeed go bad. Since it is created from alcohol, many of the essential elements that give vinegar its flavor are prone to evaporation.
A significant amount of these components typically are gone by about six months after a bottle of vinegar is opened, and most vinegars are tasteless after a year of sitting opened. Vinegar's flavor can be preserved if it is stored in a cool dark place or in a refrigerator.
Some vinegars, if stored improperly or too long, will develop a cloudy look. This cloudy substance (called "mother of vinegar" since it can be used to make more vinegar) can be filtered out with a paper coffee filter in order to salvage the vinegar. However, if either the mother or the vinegar smells bad or rotten, discard both immediately.
To learn more about food storage, continue on to the next page.