The Making of Balsamic Vinegar
Only two areas in Italy produce true traditional balsamic vinegar, Modena and neighboring Reggio Emilia. True balsamic vinegar is made from a reduction of pressed Trebbiano and Lambrusco grapes. The resulting thick syrup, called mosto cotto in Italian, is subsequently aged for a minimum of 12 years in a battery of several barrels of successively smaller sizes.
The casks are made of different woods like chestnut, cherry, oak, mulberry, ash and juniper. True balsamic vinegar is rich, glossy, deep brown in color, and has a complex flavor that balances the natural sweet and sour elements of the cooked grape juice with hints of wood from the casks..
Modena uses a system to indicate the age of its balsamic vinegars (Aceto Balsamico Tradizionale di Modena). A white-colored cap means the vinegar has aged for at least 12 years and a gold cap bearing the designation extra vecchio (extra-old) shows the vinegar has aged for 25 years or more.