Say cheese

It’s hard to beat the delicious taste of a stretchy strand of cheese on a pizza. But why does cheese get so gooey? And why are some cheeses better than others when it comes to your favourite dinner?

Humans have loved cheese since before recorded time – we believe people have made it for at least 10,000 years. And while there are thousands of different flavours and varieties (the world record for the most different types of cheese on a single pizza is 1001), they’re all made in pretty much the same way. First, cheesemakers add bacteria to milk. This produces lactic acid, causing the milk to curdle. This increased acidity causes a protein called casein to begin to tangle, turning into a solid mass – your milk begins to go off and you can scoop out the solids, called curds, to make cheese.

Untangling proteins

It’s what happens next that determines whether your cheese is stringy. Proteins are long chains of amino acids, linked together by peptide bonds – a specific type of covalent bond that occurs between a carbon atom of one amino acid and a nitrogen atom on another. These chains can stretch for thousands of amino acids in length. If you prepare your cheese in a way that pulls these protein chains out, rather than keeping them scrunched up, you’re going to get a naturally stretchy cheese.

You need exactly the right amount of acidity (about pH 5–5.4) to get the maximum stretch possible

A great example is mozzarella. Cheesemakers first put cheese curds into hot, salty water, causing the protein strands to uncurl. By repeatedly stretching and compressing the strands, they become fully untangled, resulting in a cheese that’s naturally stretchy. Food companies make cheese strings in a similar way, although there’s a final part of the process: they’re squished through the equivalent of a Play-Doh extruder, ensuring most of the cheese fibres line up the same way. The result is a processed stick that you can peel apart with your fingertips.

Controlling acidity

Pulling out proteins is only part of the secret. Another key part of the cheesemaking process is to control its acidity. Electrostatic forces, hydrophobic forces and even weak hydrogen bonds hold cheese together. If your cheese isn’t acidic enough, such as halloumi, bonding between the strands means they won’t move. Similarly, if the cheese is too acidic, such as feta, the acid will cause the electrostatic forces to become so great the protein strands won’t slide beside each other. You need exactly the right amount of acidity (about pH 5–5.4) to get the maximum stretch possible.

Tyramine terrors

Stretchy cheese is also great for another reason: it’s less likely to give you a migraine or nightmares. Tyramine, an amine caused by the breakdown of the amino acid tyrosine, causes these terrors. Tyramine is a key part of why some foods taste sharp – like cheddar, stilton and parmesan. As we don’t want stretchy cheese to be too old (eventually its acidity causes proteins to break down and make the cheese rubbery), stringy cheeses are generally low in tyramine.

There’s one last box you must tick for yummy cheese on a pizza: melting it at exactly the right temperature. This is a delicate balancing act, which depends on what else is in the cheese. For instance, a cheese with a low moisture level will melt at a higher temperature, while a cheese that’s high in fat is likely to brown, rather than become the nice, smooth goop you want. For mozzarella, the ideal temperature is about 55–60 degrees Celsius. 

If you can do it right, the results are startling. In 2023, Doritos set the world record for the longest cheese pull. They used a helicopter to dunk a 1.2 metre-wide nacho into a blend of 120 kilograms of mozzarella and cheddar. Pulling the cheese out, the team managed to get it to stretch an impressive 15 metres into the air.