It sounds delightfully nerdy, and just a tad over the top, but there is actually a very serious question to be answered: what kind of cheese works best on a pizza? The obvious answer is, of course, mozzarella – the most common pizza cheese. Reassuringly, this is what Bryony James and her team confirmed. But now we know exactly why mozzarella works so well and why, say, cheddar will never keep the customer satisfied.

Not every cheese blisters in such a tasty fashion, says James in a video accompanying the paper. “It is dictated by a combination of the composition and the mechanical properties of the cheese itself, as well as every other component of the pizza,” she explains.

To investigate, the team sprinkled grated mozzarella, cheddar, colby, edam, emmental, gruyere, and provolone on pizza crusts and baked them in an oven for a set time. Then the pizzas were shunted under a camera to be photographed for computer analysis. The software quantified the colour uniformity of the cheeses, with high uniformity meaning that there were no browned spots. Each cheese was also put through its paces in a standard panel of cheese tests, assessing its stretchiness, moisture content, how much oil it releases as it melts, and at what temperature it melts.

Perfect bubble

What the researchers were measuring with their software was the result of a very specific chain of events related to those properties. As cheese heats up, the water trapped within it – between strands of protein and globules of fat – starts to boil. It evaporates into steam, which gathers together to make a growing bubble in the cheese. If the cheese becomes elastic as it melts, the bubble will be able to stretch large. If the cheese is less stretchy, the bubble will stay small. Meanwhile, as the steam has been consolidating itself into a bubble, oil leaks out of the melting cheese to form a slick on top of the pizza. The top of a large bubble will break the surface of the oil and be exposed directly to the oven's heat, which will evaporate the rest of the water in the cheese and brown it. But if there is too much oil, even a large bubble won't break through the layer and it will remain a more pasty shade.