# Whimsical: Formula for the perfect pizza

## Researchers determine the physical background of pizza baking

Crispy, thin and with a juicy topping: That's how the perfect pizza should be. What physics is behind the optimal pizza and what role it plays the oven, scientists have now recalculated. Their "pizza formula" reveals: Pizza Margherita succeeds in the classic stone oven best at 330 degrees and two minutes baking time. In the domestic stove, however, 230 degrees and just under three minutes are optimal.

Anyone who thinks that physics only plays a role in the distant spheres of science and research is wrong. Because physics is everywhere in our everyday lives. The range extends from the behavior of our laces over phenomena such as soap bubbles, drying drops or the bubbles in the champagne to the trend drink Latte Macchiato or the hidden secrets of the water.

### Physics of baking

Now, Andrey Varlamov of the Materials Research Institute in Rome and his colleagues have chosen one of the most popular foods worldwide: pizza. Typical for them is a base of thin, crispy baked dough, and on top a juicy topping with tomato sauce, spices, mozzarella cheese and, depending on the variant, various other ingredients. Italian pizza bakers traditionally bake their pizza in a brick oven fired with wood.

But what is the physical secret of the perfectly baked pizza? The researchers have now determined, in which they calculated, among other things, the thermal conductivity of the furnace stones or furnace steel at home stove, but also the thermal radiation in the oven and the heat dissipation within the pizza. From the combination of these parameters, they then created a formula for the perfectly baked pizza.

### Conductivity of the material crucial

"We start by calculating the temperature at the interface between the pizza and the oven surface on which it lies, " the researchers explain. In the case of the stone oven, a tempering temperature of 330 degrees is the best for pizza bakers. Due to the relatively low thermal conductivity of the oven stones, the temperature at the bottom of the pizza is only around 208 degrees - perfect for a crispy bottom. display

The classic: the pizza Margherita. The physicists have used their example for their calculations. ElfQrin (Valerio Capello) / CC-by-sa 3.0

The situation is different with domestic electric cookers: The steel walls of the cooker and the baking sheet have almost 20 times higher thermal conductivity. If the oven were also heated to 330 degrees, the temperature at the pizza base should be kept at 300 degrees. "That's way too much, the pizza would be charring, " Varlamov and his colleagues report. In order to bring the pizza crust at home to the optimum crispy temperature of around 210 degrees, the setting in the electric cooker reaches 230 degrees.

### Radiation heat and evaporation determine cooking time

However, two factors play a role in the baking time: the

thermal radiation and the evaporation of water from the pizza. Because the walls and the floor heat up evenly in the all-round brick oven, the entire interior is filled with strong thermal radiation: "The pizza becomes continuous due to this flow of infrared radiation hit and heated from all sides, "report Varlamov and his colleagues.

The intensity of this heat radiation in the stone oven is 7.5 kilowatts per square meter, as the physicists calculated. "This means that every square centimeter of our pizza gets an energy of just under 0.75 joules per second, " the researchers said. 1.1 kilowatts of this energy is the pizza but by evaporation of water from dough and coating again from that is about 15 percent. This results in a baking time for the stone oven pizza of 125 seconds Bis almost exactly two minutes until the bottom is crispy and the topping is cooked.

### Electric stove takes longer

Unlike the pizza from the local oven: In this stove, the heat radiation is much lower. The pizza only receives a radiation energy of about 3.6 kilowatts per square meter that is less than half as much as the stone oven, as the researchers determined. At the same time, however, the loss of energy due to the evaporation of water remains the same. So that the pizza is baked properly, it takes therefore much longer in the electric cooker: 170 seconds and thus almost three minutes should be it already.

And the researchers have another tip for ambitious pizza bakers: If the pizza is more lavishly occupied than the classic margherita, it needs even longer in the stone oven. The pros then bake their pizza normally for two minutes and then lift it slightly with the slider for another 30 seconds, so that the heat radiation cooks the coating without burning the floor. (Physics Education, 2018; doi: 10.1088 / 1361-6552 / aadc2e)

(arXiv, 13.11.2018 - NPO)