Real Parmesan Cheese is only made in Italy and protected by the PDO designation.
Imitation Parmesan Cheese is made in the USA but to get real Parmesan Cheese it would be made only in Italy.
Parmesan Cheese is made of unpasteurized cow's milk which is and the whole milk of the morning milking is mixed with the naturally skimmed milk (which is made by keeping milk in large shallow tanks to allow the cream to separate) of the previous evening's milking, resulting in a part skim mixture.
Grated Parmesan Cheese that remains sealed with last up to 1 to 2 years.
The grated Parmesan Cheese will remain safe to eat after 2 years but it loses it's freshness the longer it sits.
Once opened the Grated Parmesan Cheese will last for 6 months to a year.
If you notice a change in the color or the grated Parmesan Cheese has a bad smell to it or it becomes clumpy or has mold in it then throw it out.
When Parmesan cheese is bad or is going bad the Parmesan Cheese will start to change color from the white color to a more yellow color.
This change in color is an indicator of the Parmesan Cheese going bad and if the color of the Parmesan Cheese changes from white to a more yellow color then it's bad and should be thrown out.
Also when Parmesan Cheese goes bad it will start having a bad smell to it along with the change in color and if you notice a bad smell from the Parmesan Cheese or it has changed colors then it's bad and should be thrown out.
Fresh Parmesan Cheese should be a white or beige color.
Sometimes mold may also be present in the bad Parmesan Cheese and if so throw it out.
Blocks of Parmesan Cheese are good for about 6 weeks once opened and if it's Parmesan Cheese that is grated for putting on Pizza and other things it can last up to a year unopened but once opened the Parmesan Cheese will last for about 6 months.