Q. Can balsamic vinegar go bad? A bottle that had been in the pantry about a year turned into globs of a jelly-like substance.
Vinegar in general has a very long shelf life. Older bottles of wine-based vinegars might get sediment at the bottom, and sometimes they develop a growth of what is called “mother of vinegar,” the natural mold that is used to make new batches of vinegar. It looks like a thin sheet floating in a bottle.
True aged balsamicos that can cost more than $100 a bottle. With cheap balsamic-flavored vinegars, manufacturers sometimes add caramel flavoring or sweeteners to mimic the true balsamic taste.
In this case, it sounds like the vinegar thickened up from sugar. It could be that the cap wasn’t tight and allowed the vinegar to evaporate. If that’s the case, it probably won’t taste like it’s supposed to and you’ll be better off just pitching it out.