Vinegar is wine that has gone bad. The term vinegar is actually a combination of two French words, vin and aigre, which translates to sour wine. And that is what vinegar really is, a sour wine. Knowing how vinegar is produced helps us understand whether or not vinegar gets spoiled and if it does how long vinegar lasts. Acetobacteria are a type of bacteria that feed on the alcohol present in wine and produce an acid as a result. These bacteria work similarly to the yeast that feed on the sugars in grape juice, creating alcohol as a by-product. Acetobacteria feeds on the alcohol and create acetic acid as a by-product. And this acid is what gives the vinegar the characteristic sharp taste.
Because of its high acidity, vinegar is self-preserving. It does not need to be placed in the refrigerator. And so the shelf life of a bottle of vinegar is quite indefinite. I’m not saying that it does not get expired, but it can be stored and used for a long time. If you are asking if vinegar can get spoiled, well, not really. Because of this self-preserving nature, vinegar will not get spoiled. However, if you ask if it can go bad, the answer is yes.
Vinegar can go bad if stored for a long time or improperly. If the vinegar is exposed to heat and light, it would most likely develop a haze or some sediment floating in the bottle of vinegar. This sediment or haze is called the “mother” of vinegar. The “mother” is actually cellulose produced by the bacteria in the vinegar. It is not harmful in anyway. All you really have to do is to filter the “mother” out of the vinegar and you can enjoy it again. Most manufacturers pasteurize their products before bottling to prevent such things from forming while the bottles of vinegars sit in stores. But once you open the bottle, your vinegar is already exposed and this is why the “mother” is seen a long time after opening the bottle of vinegar. In this case, the vinegar is not spoiled but it has somehow deteriorated. You wouldn’t want to keep on filtering the “mother” from your vinegar, would you?
Vinegar can also lose some of its flavor and color after a long time. And in this case, the vinegar has gone bad. It’s not exactly toxic or harmful, but you don’t get the same flavor from it anymore. And since there are many different types of vinegar, you want to be able to enjoy the flavor of that particular type.