Ingredient

Mozzarella

Mozzarella comes in two forms that share a name and almost nothing else. Fresh mozzarella sits in liquid, is soft and milky, and is very high in water. Block or low-moisture mozzarella is firm, dry, and made to melt and brown. Using the first where the second is wanted is the single commonest cause of a soggy home pizza.

The mozzarellas

Mozzarella di bufala

Made from water buffalo milk, in Campania, PDO-protected. Softest, richest, tangiest, wettest. For eating cold — with tomatoes, with prosciutto, torn over a salad.

Fior di latte

The same style made from cow's milk. Milder, firmer, less expensive, slightly less wet. Good cold and usable on pizza with care.

Block / low-moisture mozzarella

Aged briefly and dried. Firm, sliceable, gratable, much less water. Melts and browns and stretches. This is pizzeria and takeaway pizza cheese.

Burrata

A mozzarella shell filled with cream and shredded curd. Extremely rich. Never cooked — it is a cold dish.

Scamorza

Mozzarella aged and often smoked. Firm, melts well, distinctly savoury.

Pre-grated

Coated with starch or cellulose to stop it clumping, which affects the melt slightly. Convenient; not quite as good.

The soggy pizza problem

Fresh mozzarella is around sixty per cent water, and that water has to go somewhere. On a pizza it goes into the base.

In a wood-fired oven at very high temperature the pizza cooks in ninety seconds and the water largely turns to steam and leaves. In a domestic oven at a much lower temperature over ten minutes, it soaks downwards, and the middle of the pizza comes out pale and wet.

The answers, in order of effectiveness. Use block mozzarella, or a mixture of block and fresh. Drain and dry the fresh mozzarella thoroughly — tear it, spread it on kitchen paper, and leave it for half an hour or more; you will be surprised how much liquid comes out. Tear rather than slice, so the pieces are irregular and there are gaps for steam to escape. Add fresh mozzarella part way through the bake rather than at the start. And get the oven as hot as it will go, with a preheated stone or steel, which is worth more than any cheese decision.

Using each one

• Buffalo mozzarella, cold and torn — with good tomatoes, basil and oil; with peaches and prosciutto; on a plate with nothing but salt and oil. Bring it to room temperature first, which makes a considerable difference.
• Never cook buffalo mozzarella hard. It is expensive and its delicacy is precisely what heat destroys.
• Block mozzarella, grated — on pizza, in lasagne, in a bake, in a toastie. This is what it is for.
• In a caprese, fresh, at room temperature, salted just before serving.
• Fried — as mozzarella in carrozza, or crumbed and fried, where block or fior di latte holds together and buffalo does not.
• Burrata, cold, torn open over something — roasted tomatoes, grilled vegetables, good bread. Never heated.
• Save the liquid fresh mozzarella sits in. It is lightly salted whey and is worth adding to a dough or a soup rather than pouring away.

How it is made, and where the stretch comes from

Mozzarella is a pasta filata cheese — a "spun paste" — and that process is what gives it its texture.

The curd is left to acidify until it reaches a particular point, then it is bathed in very hot water and stretched and folded repeatedly, like dough. That working aligns the proteins into long parallel fibres rather than the random network most cheeses have, which is why fresh mozzarella pulls apart in strands rather than crumbling.

It is also the origin of the stretch when block mozzarella melts. Those aligned protein fibres soften and slide past one another while staying connected, so the cheese extends rather than flowing apart. Cheddar has no such alignment and simply melts.

The same technique produces provolone, scamorza, caciocavallo and the string cheese that is sold precisely because it pulls into threads. It is a family, and the stretching is what they have in common.

Common questions