<<Disclaimer: Verify this information before applying it to your situation.>> I happened to stumble upon the fact that one of our "safe" restaurants uses distilled vinegar to preserve their lettuce. When asked if this was a common restaurant practice, our wait person assured us it was. The manager was nice enough to prepare a salad without the vinegar, but I wonder how many times I have eaten a salad which has been doused in distilled vinegar! Has anyone else heard of this practice?