Red wine vinegar is the everyday sour of Western cooking — red wine soured by acetic-acid bacteria into a bright, ruby-hued acid. It is the classic vinegar of the French and Italian kitchen: the acid in a shaken vinaigrette, the deglazing splash in a pan sauce, the tang in a marinade or a quick pickle. Sharper and more astringent than balsamic and less fruity than cider vinegar, it carries the tannin, colour and grape character of the wine it came from.