 Judging from the advice given in many medieval documents on how to salvage wine that bore signs of going bad, preservation must have been a widespread problem.Even if vinegar was a common ingredient, there was only so much of it that could be used.In the 14th-century cookbook "Le Viandier" there are several methods for salvaging spoiling wine; making sure that the wine barrels are always topped up or adding a mixture of dried and boiled white grape seeds with the ash of dried and burnt lees of white wine were both effective bactericides, even if the chemical processes were not understood at the time.