In the wooden barrel, it obtains the flavor of the wood, that's why every year, vinegar is transferred to a different type of wooden barrel such as oak, chestnut, ash, mulberry and juniper. Balsamic vinegar which is aged for three to five years is referred to as young, the one which is matured for six to twelve years is called middle aged, and the one which is matured for twelve years and above is called old.