You may think that as long as you're buying real Parmigiano-Reggiano, your getting the best parm your money can buy, but it turns out that cheese closest to the rind is the tastiest.
The secret is in the tasty tyrosine crystals, which form when as the cheese ages. Not only did the good folks at America's Test Kitchen count more crystals on the outer pieces, but taste testers found those pieces to be "nutty, complex, and pleasantly crumbly," while the pieces of cheese taken from the center of the wheel were "mild, with a smoother, almost plastic-y texture."
Watch the video to delve in deep to the science behind tyrosine crystal formation, but the next time you're in the grocery store looking for that perfect piece of parm, be sure grab a chunk from the edge.
Science: How to Buy the Best Parmesan Cheese [America's Test Kitchen (YouTube)]