The Science Behind the Perfect Deep Dish Pizza

Much has been made of the art of pizza making. But baking the perfect pie is more than an artform: from the oven temperature, to the composition of the crust, and even the flavor profile of your favored toppings, crafting the ultimate pizza can really be broken down into a science.

The composition of the quintessential Neopolitan pizza has been the subject of heated analysis for decades, but what about the archetypal Chicagoan food stuff: the deep dish? Chicago-style deep-dish pizza is very different from a tradition Italian pie. As the name suggests, the crust is much deeper, there’s a lot more sauce, and the toppings are layered in a different order from its Italian counterpart. And importantly, these differences mean that the science behind baking a deep dish is also different from that of a thin crust. So, just how do you craft the perfect deep-dish pizza?

The starting point for any pizza is, unsurprisingly, the dough. As we’ve established, the crust of a deep-dish pizza is very different from the dough of a New York- or Italian-style pizza. Whilst these flatter incarnations only have dough on the bottom of the pizza, a Chicago style pizza has a crust that covers the side, too. And that structural difference requires the dough to be flakey and crispy.

Enter: fat.

Most regular pizza doughs contain very little or no fat. Instead, they’re made from flour, water, yeast – and occasionally, olive oil – which gives them that familiar bread-like texture. Conversely, a deep-dish pizza dough is almost a dough-pastry hybrid, with a high fat-to-flour ratio, which comes from the inclusion of corn oil or butter. This works well for two main reasons: First, fat gives the dough a stronger structure, meaning that the dough can be used to make the sides of the pizza. Secondly, fat is critical for keeping the base of the pizza nice and crispy. For anyone who’s watched the Great British Baking Show, you’ll know that a fundamental no-go in the world of baking is a soggy bottom – and that’s also true for a pizza. The high fat composition of a deep-dish dough means that the fat can coat a high proportion of the flour particles. Because fat repels moisture, this stops the liquid in the sauce from seeping into the dough. As a result, the crust stays crispy on the bottom, and the sauce stays in the pizza, where we want it to be.

Now that you’ve got your dough, it’s time to consider the other important pizza components: tomato sauce, cheese, and extra toppings. Given the structure of a Chicago style pizza, the ratios and layering of these compared to a thinner crust pizza are quite different. For one, a deep-dish pizza uses more sauce than a thin crust. And since the main component of tomato sauce is water, this can ruin all the effort of making the perfect crispy crust if the pizza isn’t constructed properly. Although the fat in the crust acts a good barrier to a soggy base, another critical pizza component that helps with this is the cheese.

No deep-dish pizza is complete without cheese, and the vast majority of Chicago deep-dish pizza restaurants use the same type of cheese – Wisconsin mozzarella. Mozzarella is the perfect stringy melting cheese, and it acts like this because of the way it is manufactured. Like all cheese, mozzarella is made of milk: Italian buffalo milk is used to make Italian buffalo mozzarella, and cow’s milk makes Wisconsin mozzarella. Milk is largely made of protein, fat, and water. Milk proteins are tightly coiled up chains of molecules, and during the cheese manufacturing process, these proteins are separated out to make curds.

These properties make mozzarella an excellent melting cheese to use on pizza, but the high fat content of mozzarella also aids with its construction. In a deep-dish pizza, the mozzarella is the first layer on top of the dough – as opposed to the top layer in a thin crust pizza. By making a cheese layer between the sauce and the dough, along with using a buttery dough, this makes a dual ‘barrier,’ guarding against a soggy crust.

The final element of our deep-dish pizzas are the toppings, and perhaps unsurprisingly, the most popular ingredient for Chicago deep-dish is sausage. Regardless of any city-based allegiance, there’s also a science behind what makes the perfect Chicagoan sausage – and also what makes it a preferable pizza ingredient. First of all, sausage is a high-fat meat, with an approximate fat content of 30%. The high-fat component keeps the sausage solid at room temperature, but makes it juicy and tender when hot. Fat is also useful for absorbing any spices that are added to the sausage meat. But the most important ingredient in sausage isn’t actually the fat: it’s the salt.

Proteins in meat are bundled into fibers that are fairly complex and tough. Grinding and mixing meat alone does little to break down those fibers – you just end up with shorter fibers that are equally tough to chew. But humble sodium chloride (table salt) works wonders for tenderizing these fibers: by adding salt to surface of the meat, water migrates from inside the meat (where there is a low concentration of salt) to outside of the meat, through the process of osmosis. When the water reaches the salt, it dissolves, which makes a briney liquid that is capable of breaking down some of the tough meat proteins. This means that salted meat has a far preferable consistency for grinding and kneading, and also encourages the blending of meat with the fat to improve the texture when cooked. In terms of the construction of the pizza, the salt and spice element of the sausage complements the acid (tomato sauce) and fat (cheese), making a complete flavor profile.

Now that all of the pizza components are ready to go, it’s time to bake. As we’ve seen, deep-dish pizza is made in distinct layers: the cheese is layered on the dough, followed by the sausage, and the sauce on top. Depending on the size, your pizza needs to bake for 30-40 minutes at 425°F (the perfect pizza oven temperature), and that requires a metal pan that can handle the heat. Lou Malnati’s, one of the stalwarts of the Chicago pizza scene, reportedly bakes their pizza in an aluminum pan: a lightweight metal with excellent thermal conductive properties. That means the pan not only heats up quickly, but it also heats evenly, ensuring that the pizza cooks consistently without a burnt crust.

So there you have it. Whether you’re a Giordano’s, Gino’s East, or Lou Malnati’s fan, the next time you order takeout, you’ll know a bit more about what goes into your favorite deep-dish slice.

Helen Robertson is a postdoctoral scholar at the University of Chicago, where she is investigating the evolution of genomes and gene regulation in different marine animals. Prior to this she obtained a PhD in evolutionary biology from University College London. Outside of the lab she is interested in science communication and likes to write about science in society and new life sciences research.

Author(s)