The Food Lab: Why Does Pepperoni Curl?
This isn't a hard question. There's two reasons pepperonis curl. One is that the top is cooking faster than the bottom, and as with any piece of meat that will cause it to curl towards the surface being cooked faster.<p>The other reason is that the edge of the pepperoni cooks faster than the middle, that means that the edge experiences tension which causes the pepperoni to fold.