The Delicious Cheese Science of Melt & Stretch

Why does cheese melt? & What makes cheese stretchy

We all know and love the decadence of melted cheese but how many of us understand the science behind the ooze and the stretch? Our newest Level Three Advanced Course, Presenting & Serving, contains a section titled ‘Cooking with Cheese’ aimed at deepening the understanding of how various cheeses can be used in gastronomy, and why some are better suited to some dishes than others.  

This article will take a look into the (literal) melting pot of fat, protein, moisture and pH and see how they come together to create cheeses with very different behaviours in the kitchen.

Cheese Melt

First of all, we need to understand a bit about the structure of the cheese itself. In simple terms, cheese is a matrix of proteins bonded by calcium with fat and water trapped inside. The amount of fat and water varies from cheese to cheese, of course, and this is what will determine a lot of a cheese’s meltability or otherwise.

The first cheese in this diagram has less fat than the bottom cheese and therefore the curd matrix is more densely connected.

As the fat melts, the matrix is weakened as gaps are left by the fat globules (which are much larger than the proteins). This is what causes the cheese to melt.

• Above 30°C – fat begins to melt
• Above 40°C – milk fat is liquid
• Above 60°C – protein matrix begins to melt

Soft cheeses

Predominately lactic-set soft cheeses

Whilst young cheeses of this type are typically very high in moisture, the acidity of the cheese dissolves a large amount of the calcium and therefore the bonds holding the matrix together. This is why lactic cheeses become so firm and dry as they aged (think, aged Crottin de Chavignol). That moisture is lost very quickly in cooking and the weak structure of the cheese prevents it from spreading much as it melts, though it will then mix well into a dish. Think of how well a swirl of fresh goat or cow curd in a rich earthy bortsch mixes in, adding a zing to the earthy soup.

Older cheeses, with the moisture already lost hold their shape under heat and release their warm, peppery flavours when grilled.

Predominately rennet-set soft cheeses

This type of cheese (think Brie de Meaux and Camembert), with its tendency to bulge as they’re cut, waiting to spill out from under the rind, are the opposite end of the scale to the soft lactics.

The strength of the bonds, from a long hardening time after renneting, remains in place due to the minimal acidity and holds the moisture and fat firmly in place in the soft, sticky paste.

So, how do they melt? Instead of dissolving calcium to weaken the structure, we can rely on proteolysis. Think of that liquid underneath the rind. That’s the result of the proteins breaking down and becoming liquid, and heat can help that along a little. This is why some Camembert styles bake better than others.

Best Time to Bake Camembert

According to Savencia’s L’école du Fromage, the optimum point for baking a Camembert is somewhere between 35 and 45 days old – the perfect point where the proteins have broken down enough that when heated the melting fat will cause the matrix to break down into a delicious, scoopable goo.

Hard cheeses

The same principles apply to hard cheeses, though the lack of moisture in the uncooked cheese does have some effect. Water molecules are also trapped in the curd matrix along with fat globules, and so the less moisture in a cheese then the more tightly knit the matrix is.

Parmesan Tuile

This is why grana-style cheeses can be used to make delicious tuiles, or a crispy crust on the top of pasta bake. The low moisture and fat content of this style of cheese cause it to melt only at higher temperatures, with minimal spreading, while retaining its shape and developing a crisp texture.

The Ultimate Fondue Cheese

So, what about the ultimate fondue cheeses? Those classic Alpine styles in the hard, cooked category.

They have slightly higher fat than the grana styles and due to the nature of the NSLABs present (responsible for so much of those delicious, roasted nut and butterscotch flavours) and the action of bacteria on the washed, dry-brushed rind, there is a lot of enzymatic activity going on as these cheeses age.

This means lots of proteolysis. Those delicious flavours? Those of you who have studied the Level Three Tasting course will know that it’s only possible with the breakdown of proteins into aromatic compounds. This is how the texture changes from young Alpines, where we can see the elastic ‘bend’ in the cheese off the iron to the clean ‘snap’ when you break off a chunk of aged cheese whilst standing in front of the fridge (surely that’s not just me?!).

So when a perfectly aged Beaufort, Comté, Templegall, or Le Gruyère AOP is heated in the fondue pot to a high enough temperature it breaks down completely into a smooth, thick liquid with just enough structure to create those glorious strings as the bread is pulled out.

Speaking of strings, we can’t talk about cooking cheese without mentioning the pasta filata cheeses. How to achieve that perfect stretch on the slice of pizza…

When making a cheese like mozzarella getting the stretch right means hitting the point in the acidification when there is enough dissolved calcium to break up the curd matrix, but enough retained calcium to hold things together.

Typically this is between pH 5.4 and 5.2. In this range, there is a little dissolution of calcium which allows the proteins that are still joined together to respond to the heat as the curd is submerged in the hot whey, and ‘line up’ to give that characteristic texture. This is not dissimilar to what happens when bread is kneaded.

This diagram from the Presenting & Serving learning road shows how the dissolved calcium (blue) allows enough movement in the curd for it to ‘line up’ when heated and remain in place due to the retained calcium (green).

Lining up the proteins when the curd is stretched (literal translation of pasta filata) is what gives these cheeses their unbeatable stringiness when cooked.

Cooking with cheese is a true delight, even more so when you can apply your knowledge to selecting exactly the right cheese for the dish.