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Pizza is simply one of the finest culinary inventions to grace the planet Earth. That magical combination of crust, cheese, sauce, and toppings has been delighting mouths (and burning them, if you’re not careful!) for decades. You can have thick crust, thin crust, red sauce, white sauce, no sauce, plain or piled high with pepperoni, sausage, onions, mushrooms, and whatever else you want. But no matter how you top your pizza, you need to have that one all-important ingredient: a good, thick layer of wonderful, melty, stringy mozzarella cheese. For a pizza that is cheeseless is hardly a pizza at all. In this Saturday Science, we’ll experiment with different kinds of cheeses and learn how and why they melt.
Materials:
- A cookie sheet
- An oven
- Potholders
- Wax paper or parchment paper
- A cheese grater
- A fork
- Cheese! [Mozzarella (of course!), cheddar or Colby, Parmesan or Romano, blue cheese or gorgonzola, and feta or ricotta]
- An adult
Process:
- Preheat your oven to around 300 degrees.
- While your oven is heating up, cover your cookie sheet with wax or parchment paper, so all the melty cheese doesn’t stick to it.
- Have an adult help you make little piles of your various cheeses spread out evenly across the cookie sheet. Some of them, like blue cheese and feta cheese, can be crumbled by hand. Others you may need to shred with the cheese grater (unless they came pre-shredded in a bag). Shredding or crumbling the cheese will help it melt a little more easily.
- As you’re crumbling and grating your cheese, observe the different physical properties. Are some cheeses harder than others? Wetter? More difficult to grate?
- Form a hypothesis: how do you think each cheese will melt based on its physical properties?
- When your oven is heated up, have your adult put your cheeses on the middle rack. Check it after about five minutes. If your cheeses haven’t melted, give it another minute or two.
- When a few of your cheeses are really good and melty, go ahead and have your adult pull the cookie sheet out of the oven.
- Carefully remove the wax paper from the cookie sheet and move it somewhere else so you can examine your melty cheese without accidentally burning yourself on hot metal.
- Use your fork to poke and probe the different cheeses. Chances are they each melted differently. What are the differences among all your cheeses? Was your hypothesis correct? What ways could you use all these different kinds of melty cheese to make different meals?
Summary
It may seem weird, but there’s a whole lot of science going on here to explain why all your cheeses melted in different ways (or didn’t really melt at all). When you apply heat to make the cheese melt, two things happen. First, the fat in the cheese goes from solid to liquid. Second, when the cheese gets even hotter, the protein that makes up much of most cheeses (called casein) starts to break down. The bonds that hold the protein molecules together start to break, and the cheese goes from solid to liquid.
A cheese's ability to melt is affected by all sorts of things: how much moisture, fat, and salt is in the cheese, how much calcium or acid it contains, and even how the milk was curdled. In general, cheeses that are high in moisture and fat melt well, but if there’s extra salt, acid, or calcium then that might not be true.
The reason we used the five types of cheese we did is that each of them melts differently. Cheddar and Colby are both good melters because they’re each moist, fatty, and not too salty. Parmesan and Romano are both aged cheeses, so they have less moisture. They’re also high in salt, so they don’t tend to melt very well. Gorgonzola and blue cheese melt almost too well because the mold cultures used to give them their flavors break down proteins and calcium, which makes them go extra liquidy when you apply heat. Feta and ricotta have more calcium than other cheeses, and that calcium holds the casein proteins together so well that they don’t melt at all!
Mozzarella, of course, melts really well, which makes it an ideal cheese for pizza. But it does something different from other cheeses when it melts: it gets stringy. You’ve probably had strings of mozzarella down your chin after eating a fresh slice of pizza. The difference between mozzarella and other melty cheeses (like cheddar, for example) is that mozzarella has just a little bit more calcium holding the casein proteins together. They still break down under heat, but they hold together just enough to make long strings when you pull on them with your mouth.
There are hundreds, if not thousands, of different types of cheese all around the world, and they all melt just a bit differently. Some are good for pizza, and some aren’t, but that doesn’t mean that each and every cheese isn’t delicious in its own way!
