But if you think this is as simple as throwing it in a pan, you’d only partially be right. Let’s dive into the chemistry at play—don’t worry, there won’t be a quiz. The amount of melt or stretch from the cheese depends on four components: protein, fat, water, and acid.
The main protein found in cheese is called casein protein. This protein works in a highly specialized network known as a micelle, think of this a bunch of casein molecules put together quite nicely in separate groups. In the cheese making process, these micelles come together to form a larger network filled with fat and water [serum]. In the case of grilled cheese, when heat is applied the larger network begins to shrink and forces the serum out. This allows micelle groups to begin fusing together, making fewer groups—something necessary for the cheese to give us that mouthwatering stretch.
At the center of these protein micelles are fat globules, these are little droplets of fat that do not interact specifically with the micelles. Since the networks of protein are small compared to the fat globule, the fat can break up the groups—causing them to spread further apart—allowing the cheese to melt at a lower temperature than a cheese lower in fat.
The amount of moisture found in a cheese also plays a role in how well it will melt and stretch. As it goes for most chemical processes, water serves as a type of buffer in cheese. Cheeses with higher moisture content tend to melt better. These would be cheeses like Mozzarella or a young Gouda.
To have a quality melting cheese, you need the correct pH (level of acidity). If the pH drops too low, the amount of stretch in the cheese may be lost. Acid is crucial to the melt and stretch of cheese. Acid can be added in the cheese-making process or develop as the cultures (bacteria) work over time. When a cheese is made using acid (e.g. cottage cheese), the high amount of acid causes the micelle networks to become attracted to each other forming tight groups. This prevents the cheese from fully melting—it may soften with heat, but it will not provide a nice stretch.
The cheese used shouldn’t be aged over one year and should have the right amount of protein, fat, moisture, and acidity. Some of our stretchiest, meltiest local favorites include: