A sour is spirit, citrus and sugar. Add an egg white and the same drink turns silky, with a pale foam head that holds for the whole glass. The white adds almost no flavour. What it adds is proteins, and shaking turns them into a net of tiny bubbles. This piece shows how to build that foam, why the order of the shake matters, and how to get it without egg.
Egg white is mostly water and protein. When you shake it hard, the proteins unfold and line up around the air bubbles you whip in, which stops the bubbles from collapsing. Fat and oil interfere with this, which is why a clean shaker and no yolk matter. Cold ice also works against you at first: ice and water dilute the white before it has trapped any air.
That is the whole reason for the two famous tricks. Both split the shake in two: one hard shake with ice to chill and dilute, and one without ice to build foam. They only differ in which comes first.
| Ingredient | Measure |
|---|---|
| Whiskey (bourbon or rye) | 50 ml (1⅔ oz) |
| Fresh lemon juice | 25 ml (⅚ oz) |
| Sugar syrup, 1:1 | 15 ml (½ oz) |
| Egg white, about one | 20–30 ml (⅔–1 oz) |
Glass: a chilled coupe or a small rocks glass. Garnish: a few drops of bitters on the foam, or nothing. The same method works for any sour: a Pisco Sour, a Clover Club or a gin sour.
The scaler counts one egg white per drink. A large white is roughly 30 ml, and for several drinks it is easier to count whites than to measure them.
Bartenders disagree, and that is worth knowing. Julie Reiner has said she tried the reverse method and got larger bubbles and a bigger head, then went back to the standard dry shake because she preferred the feel of the smaller bubbles. Others argue that diluting the white with ice first makes the foam settle quicker. Some say that with good ice and a hard shake the difference is small.
Try both once. Taste the foam, not just look at it.
If you only want one rule: shake hard, and do the iceless shake for the full ten seconds. A weak shake is the commonest reason for thin foam.
Aquafaba, the water from a tin of chickpeas, foams in a similar way and is the usual vegan swap. Start with roughly 20–30 ml per egg white, strain it first and expect to shake a little longer. Ready-made egg-free foaming products exist too. Either way the drink is no longer a classic, but it is still a good sour.
Raw egg white carries a small risk of salmonella. The risk is low, but not nil, and it is higher for pregnant women, older people, young children and anyone with a weakened immune system, who should skip raw egg. Citrus and alcohol do not reliably make it safe. Keep eggs in the fridge, use fresh clean ones, or buy pasteurised egg white, which is the safest option for drinks. Aquafaba avoids the question entirely.
The foam does not need alcohol. Swap the whiskey for 50 ml of strong cold black tea or an alcohol-free spirit, keep the lemon and syrup, and shake with the white as above. You get the same silky texture with no alcohol. As always, enjoy alcohol in moderation, and never drive after drinking.
The white needs a hard, ice-free shake to build foam. Dry shake or reverse is a matter of taste, so try both. Strain through a fine strainer for a smooth head, and use aquafaba or pasteurised white if raw egg is a worry.