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Nobody can ever seem to agree on which pizza is the best, so a team of scientists decided to call in an unbiased pizza-evaluation algorithm to determine how to compose a winning pie.
While a fair assessment of pizza quality — a pressing concern in certain food circles — would require considering everything from crust char to sauce flavor, the scientists kicked off what will hopefully be an ongoing project by zeroing in on one highly important aspect of any pie: the cheese. (This was actually a collaboration with Fonterra, a multinational dairy cooperative with a clear interest in the study's results.)
How can a pizzaiolo select a cheese that will brown and blister perfectly? Is mozzarella really best? Teasing out the science of pizza cheese is no small matter.
"Pizza browning and blistering seems like a totally trivial question," study coauthor Bryony James, Ph.D., a materials engineer at the University of Auckland, admits in a video about the study. "You stuff your pizza in the oven, and it's clearly going to brown and blister."
But there's a lot of complexity underlying what seems like a relatively simple process. The cheese itself is a complex material, and the way it ends up looking and tasting is, in part, a reaction to every other ingredient in the pizza and the way each of them transforms under high heat.
The fact that two pizzas rarely come out looking the same may be celebrated by pizza purists, but it presents a difficult problem for pizza manufacturers, who may want to provide a consistent experience or offer custom options for picky eaters. "Consumers like pizza to look a certain way," says James, who goes on to describe what is probably her ideal pie. "It should have discrete patches of that toasty cheese color," she says, "and a uniform golden brown background."
In order to do a thorough investigation of the properties required to best achieve such results, the scientists included a wide range of cheeses — not just mozzarella, which is clearly the gold standard, but also cheddar, Colby, Edam, Emmental, Gruyere, and provolone.
They sprinkled each cheese on top of a pizza base in exacting amounts and decided against using sauce so they wouldn't have to worry about an additional variable. Then each pie was baked for the same amount of time.
Some researchers may have opted to call in a panel of tasters to evaluate each pie. But humans can be fickle — not to mention expensive. So the team opted to do a machine-vision analysis of the pies instead, relying on a machine that took careful pictures and then made sense of them, using specially developed algorithms that could quantify the color and uniformity of each pizza.
The team also assessed each cheese for meltability and elasticity as well as oil and water activity.
What They Found
Turns out mozzarella is king of the pizza cheeses for a reason: "its unique stretchability," the authors, led by Xixiu Ma, conclude. It also produces high levels of bubble-making steam and low levels of free-flowing oil, which is why those bubbles brown up so nicely. But for those willing to mix it up a bit, the study revealed some interesting things.
Adding oily cheeses like Gruyere or provolone will make the pizza less burnt-looking, while sprinkling on some Colby cheese will facilitate a more uniform appearance.
Here are the photos of each cheese pizza, as well as the machine-vision analysis of its uniformity and color — mozzarella clearly produces the most varied, exciting-looking pie:
The image below shows how the various cheeses browned very differently (and that's not mold — the browned areas are outlined in green):
At the end of all this — which served as an example of the capabilities of machine-vision, not just an analysis of cheese — the authors offered this conclusion: "Different cheeses can be employed on 'gourmet' style pizzas in combination with Mozzarella."
You heard the scientists, pizzaiolos of the world: Go wild.
But for best results, don't forget to include a generous sprinkling of mozzarella.
The paper, "Quantification of Pizza Baking Properties of Different Cheeses, and Their Correlation with Cheese Functionality," was published in the August 2014 issue of The Journal of Food Science.