It is a fact that not all cheeses melt equally.
Sometimes we have to discover this the hard way, by preparing a meal that we anticipate will be ooey-gooey and utterly delightful—only to discover hard strings of cheese scattered over the surface like a platter of dry grains. Other times, a meal we prepare to be relatively healthy ends up sitting in an unexpected pool of cheese grease.
The reason why some cheeses melt gracefully and perfectly—and why others yet melt like hot crap—lies in none other than the realm of science.
There are three governing factors that will determine how well a given cheese melts:
In general, cheeses that are higher in moisture are going to melt better than cheeses that have a lower moisture content. This is a result of the strength of the cheese’s chemical structure.
A cheese will melt and flow based on the breakdown of its milk protein network. Generally speaking, that network falls apart as heat is applied to the cheese; as the network breaks down, the cheese is able to liquefy.
Cheeses that are younger have more loosely packed networks of milk protein, or casein, holding them together. For younger cheeses that are higher in moisture, the water and fat inside the cheese have more room to move around—and are more easily released—because the casein network is relaxed and open.
On the inverse, cheeses that are older and lower in moisture have more tightly packed protein networks. In these cheeses, the milk fat is tightly encased in the casein structure, which means the cheese is essentially more concentrated with fat than a younger, higher moisture cheese, which will be more concentrated with water.
But this is not to say that all aged cheeses are going to be higher in fat than all young cheeses. That, of course, depends on the recipe by which the cheese was made; some aged cheeses are made with skim or part-skim milk, and many young cheeses are made with extra cream added.
As the protein structure in an older, drier cheese breaks down, all of its highly concentrated milk fat is released—which explains why cheeses like Parmigiano Reggiano and Pecorino Romano create a nice, greasy oil slick when they melt.
This also illustrates that a cheese that is higher in fat will be a better melting cheese than one that is low in fat. Reggiano is a low-fat cheese, and Brie is a full-fat cheese.
Additionally, the cheese’s casein network is being held in place by calcium. That calcium dissolves over time, leaving behind a protein structure that is less elastic—or more brittle, however you want to imagine it.
So young Asiago will melt well, but aged Asiago will not; young Gouda will melt like a dream, but aged Gouda will become a hot mess.
You might have noticed that when you apply heat to fresher cheeses like Brie and Mozzarella, they will become stretchy before they melt. Because they don’t have the same calcium-based elasticity in their protein matrices, older cheeses won’t stretch like that; they will just go from solid to melting and flowing.
That explains why melted Mozzarella will be more globby when you start heating it, whereas properly melted aged cheddar will be creamier early on.
Of course, Mozzarella and other pasta filata cheeses are more complicated than, say, Brie, because of how they are made. When these stretched-curd cheeses are pulled, their fat is redistributed unevenly in their protein structures. That’s why Mozzarella, Queso Oaxaca, and young Provolone release a lot of oil when you warm them up.
There are also cheeses that never melt, and that is because of their pH levels.
Cheeses that are too acidic or too base will never melt. I’m talking about Paneer, Feta, Bread Cheese, Queso Fresco, Ricotta, Farmer’s Cheese, Halloumi, and even fresh Chèvre.
These cheeses will sweat (release water), but their milk protein networks will retract and hold together more tightly—the exact opposite of what happens when other cheeses melt. This is the case for cheeses that are acid-set, or which are naturally acidic (like Chèvre).
Acid-set cheeses are those that are coagulated without rennet; they are generally younger, fresher cheeses, but they just won’t melt for you like young, fresh cheeses that are rennet-set.
Washed-curd and cooked-curd cheeses are much less acidic, which means that they will be better melters. Young Goudas and Alpine-style (Swiss-type) cheeses fall into this category.
But, as I mentioned above, aged Goudas won’t melt happily for you. In general, aged Goudas are encased in hard wax. That wax acts as a barrier, which keeps moisture in and allows the casein networks to become super tight and difficult to loosen.
Now, all is not lost when it comes to cheeses you wanted to melt, but you now think you probably can’t. There are a few tricks to help you get a bad melter to become a better melter.
For starters, all cheeses will hold together when they are cold and “open up” as they warm. This is why the optimal temperature for tasting and eating cheese is around room temperature—after the cheese has sat out for at least an hour.
If you let your cheese come to room temperature before you put a fire under it, it will be more likely to comply with your melted-cheese desires.
You can also add starch to a cheese that doesn’t want to melt. That’s why many fondue recipes (like this simple one) include cornstarch—not just to keep the cheese and wine from separating, but also because we can’t always control the types of Alpine-style cheeses we have access to, and we want to ensure that the cheese melts evenly no matter what.
You also need to watch the heat when you melt cheese. If you cook a good melting cheese too quickly or at too high a heat, it can clump or burn. And nobody wants that.
A good rule of thumb is that high-moisture cheeses melt at 130⁰ Fahrenheit, aged cheeses melt at 150⁰ Fahrenheit, and low-moisture cheeses melt at 180⁰ Fahrenheit.
Of course, it also depends on the individual cheese, what you’re heating it with, in, or on, what kind of vessel it’s being heated in, and how you want it to turn out. So if you’re working with a new cheese, you might want to consult a recipe before you scorch it.
You want to have a heavenly experience with your hot cheese, not burn it at the stake.