Science Crowns Mozzarella The King Of Pizza Cheese : The Salt : NPR

The unique browning patterns on mozzarella come from the way it bubbles, James says. Since it's made by repeatedly stretching and molding fresh curds, "mozzarella has a lot of elasticity," she explains. "If you look at it under a microscope, you see it has these channels of fat surrounded by protein."

In the oven, the water in the cheese evaporates to create of steam, which causes it to bubble. Since mozzarella is so stretchy, the bubbles can expand and become fairly big. As the bubbles grow, the oil sitting on top slides off and the exposed mozzarella starts to brown. "Finally, the bubbles pop and recede back down," James says.

Cheddar isn't very elastic, so it barely bubbles, the study found. Yet a cheddar pizza will bake to an even, golden brown.In contrast, Gruyere bubbles really well but barely browns. It's a lot more oily than mozzarella, and the fat keeps the moisture in the cheese from evaporating.

via Science Crowns Mozzarella The King Of Pizza Cheese : The Salt : NPR.