Ingredient

Egg white

Egg white is about ninety per cent water and ten per cent protein, and almost nothing else. That composition explains everything it does: it sets firm and clean, it whips to many times its volume, and it contributes structure without fat or flavour.

Why it whips

Whisking does two things at once: it beats air bubbles into the liquid, and it mechanically unfolds the proteins. Those unfolded proteins spread out around the bubbles, link to one another, and form a flexible film that holds the air in place. Egg white can hold something like eight times its own volume of air this way, which is more than any other everyday ingredient.

Two things break it. Fat — even a speck of yolk or a film of grease in the bowl — physically prevents the proteins from forming the film, so the foam never builds. And over-whipping, where the proteins keep linking until the film is too tight to hold the bubbles, the water is squeezed out, and the foam turns grainy and watery. Unlike cream, over-whipped egg white cannot be rescued.

The peak stages

Lift the whisk out and look. This is the only reliable measure.

Frothy

Large loose bubbles. Nothing useful yet.

Soft peak

A peak forms and immediately flops. For folding into a mousse or a batter.

Firm peak

The peak holds and the tip curls over. The usual target.

Stiff peak

The peak stands straight. For meringue that must hold its shape. Very close to over-whipped.

Over-whipped

Dull, grainy, with liquid at the bottom. Start again.

Getting it right

• A scrupulously clean bowl — glass or metal, never plastic, which holds a film of fat however well washed.
• Not a speck of yolk. Separate each egg over a third bowl so one broken yolk does not spoil the batch.
• Room temperature whites whip to a greater volume than cold ones, though cold ones separate more cleanly.
• A pinch of cream of tartar, a few drops of lemon juice, or a copper bowl stabilises the foam and widens the margin before over-whipping.
• Add sugar gradually and after soft peaks. Added too early it inhibits the foam; added gradually it dissolves and makes the meringue glossy and stable.
• Fold, do not stir, once the foam is made. Every stir knocks air out.

What it is used for

• Meringue — whipped with sugar, in three families: French (raw sugar whisked in), Swiss (warmed over water) and Italian (hot syrup poured in). Increasingly stable in that order.
• Soufflés and mousses, where whipped white supplies the lift.
• Angel food and chiffon cakes, which use no fat at all.
• Clarifying stock and consommé — the raft. Whisked whites added to cold stock coagulate as it heats and trap the particles that cloud it.
• Coating and binding — a wash for pastry, or as glue for a crumb coating.
• Cocktails, where it produces foam and body.
• Egg white and yolk are not interchangeable in a recipe. Extra white makes cakes drier and tougher; the yolk is where the fat and emulsifying power are.

What it is good for, beyond meringue

• Clarifying stock. Whisked egg white stirred into a simmering stock traps fine particles and rises as a raft, leaving it clear. This is how consommé is made.
• Binding. In fishcakes, terrines and dumplings, where it sets and holds things together without adding fat.
• Velveting meat. A little egg white with cornflour in a stir-fry marinade gives a silky protective coating.
• A glaze. Brushed on pastry it gives a shine without the colour an egg wash provides.
• Sealing pastry, where it acts as a waterproof film.
• Freezing. Whites freeze perfectly, unlike yolks. Freeze them individually in an ice-cube tray and note how many.

Common questions