The minimum aging requirement for Parmigiano-Reggiano is 12 months.
Parmigiano-Reggiano is a protected Italian cheese made in designated areas of Emilia-Romagna and nearby parts of Lombardy. After the cheese is produced, each wheel matures for at least a year before it can receive the official designation. At around 12 months, inspectors examine every wheel; cheeses that pass may continue aging, while defective wheels are removed from the category.
Twelve months is the legal minimum, not the age most people associate with the cheese. Many wheels are sold after about 24 months, when they have a firmer texture, deeper savory flavor, and more pronounced crystalline structure. Longer aging, such as 30 or 36 months, produces a drier, more intensely flavored cheese that is especially suitable for grating.
A common mix-up is confusing the minimum with the average. The Consortium states that 24 months is roughly the average maturation period, while 12 months is the threshold.