One of my favorite things to eat on a Friday night is pizza. It can be so versatile because you can add different toppings. It’s a vessel of food that allows you to express your unique personality. But have you ever taken a second to think about what a pizza is, more to the point, what happens to the dough? Well, that’s what Bonding with Food, a chemistry class, did on a Thursday afternoon.
We studied and read in On Food and Cooking by Harold McGee, Cookwise by Shirley Corriher, and I’m Just Here for More Food by Alton Brown about different doughs, breads, and pastries. In class, we made our own dough with some variations to see what the effects were. There are two basic steps to making a pizza. The first is to the combine ingredients. Ok, simple enough. The second one is to knead the dough. I never really knew why pizzeria employees would knead the dough and toss it up in the air. Was it to show their prowess at pizza making? Could you judge the quality of the pizza by how high or how well a pizza was thrown in the air? I came to the conclusion that no, it wasn’t a bench mark for skill or quality, but actually had a much more practical reasoning behind it. Before we get to kneading, we must first look at the ingredients needed to knead.
The basic structure of dough is flour and water. But wait, can that make every kind of dough and pastry? Well, not really. There are other ingredients you can add to change the consistency and flavor of the dough. The basic structure however is water, gluten proteins (glutenin and gliadin) from the flour, and starch granules also coming from the flour. Generally, doughs with more flour than water can be manipulated by hand. The table below shows what was used in our four experimental trials.
Gluten plays a central role in pizza production. Gluten is mainly protein, proteins that are so big they may be the biggest in the natural world. The structure of these proteins is essential to the role they play in dough. Gluten is made of both glutenin and gliadin proteins. Gluten is the structure made from the combination of glutenin and gliadin.
Glutenin itself is like a long spring. When I played with springs with a kid, I would always pull them apart and they would spring back together. In much the same way, that is how glutenin acts. Glutenin proteins are attached to each other end to end by sulfur bonds between amino acids at the ends of the protein. These form long chains. Additionally, the glutenin chains are bunched together in parallel lines. These lines become entangled and gliadin proteins, acting like ball bearings, allow the glutenin chains to slide past each other without bonding. Gliadin acts as grease so that glutenin can slide over one another while the chains stretch and condense. The sum of the glutenin and gliadin structures is gluten.
As you make a pizza from scratch, many recipes will tell you to set the dough aside and wait. The purpose of this is because if you have added yeast and sugar to your dough, the dough will need some time to proof. The process of proofing has one sole purpose: to add air bubbles. Technically, they aren’t air. The yeast that is added is a biological organism that turns the sugar into carbon dioxide through biological processes. The proofing time allows the yeast time to work and create bubbles that are held by the gluten matrix.
To test differences in preparation and the effect on making pizza dough, we ran an experiment. There were four trials. Two tested the addition adding oil early in the dough process and two others had oil added late to the dough making process. Between the two with oil added early, they were further differentiated by the length of time kneaded. One was kneaded for a brief amount of time before left to proof and the other was kneaded for a considerably longer time. The same was done with the doughs that had oil added later. One was kneaded for a brief period while the other was needed for a longer amount of time.
After initial mixing, the doughs were kneaded for differing amount of time. The purpose of varying the kneading was to differ how much the gluten networks are integrated with glutenin intertwining and the gliadin becoming interspersed within the network. In addition to kneading, a process that increases the integration while also making the dough thinner is “throwing” pizza. The technique is to make a fist and throw and twist your wrist to spin it as it is in the air. The centripetal force of the rotation will uniformly stretch the dough into a circular. This is why pizzas are thrown in the air. The purpose is to create a nice, circular, and uniform pizza crust. If this fails, as it seemed to for our testing, a rolling pin is always a great option.
All you need to do now is add your favorite toppings (in class, we made a white pizza to focus on the difference between the crusts) and place in the oven for a few minutes, then out pops a fresh new pizza full of chemistry. Bon Appétit!
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