Meringue
Meringue is a foam made by whipping egg whites with sugar until they hold peaks. Baked low and slow, it becomes crisp and light; left soft, it tops pies, lightens mousses, and forms the base of buttercreams.
The science of the foam
Egg white is about 90% water and 10% protein. Whisking pushes air in and stretches the proteins at the surface of each bubble. They unfold (denature) and link up with one another, forming a flexible film that holds the air in place.
Sugar dissolves into the water and makes it thicker and more viscous, which slows drainage and stabilizes bubbles. But sugar also gets in the way of proteins unfolding, so it is added gradually after the whites reach soft peaks.
Acid such as cream of tartar or lemon juice, about 1/8 tsp per white, lowers the pH and helps the proteins bond more evenly, giving a finer, sturdier foam.
Fat is the enemy. Even a trace of yolk or grease coats the proteins and stops them from forming a strong film.
Copper bowls release a little copper that binds to one egg protein and makes the foam more stable. Cream of tartar does a similar job in glass or steel.
The three types
| Type | Method | Stability | Best for |
|---|---|---|---|
| French | Sugar added gradually to raw whipped whites | Lowest | Crisp baked meringues, pavlova, soufflés, macarons |
| Swiss | Whites and sugar warmed over simmering water to 71 °C / 160 °F, then whipped | Medium-high, dense, glossy | Swiss meringue buttercream, pie toppings |
| Italian | Sugar syrup at 118–121 °C / 245–250 °F streamed into whipped whites | Highest | Italian buttercream, mousses, Baked Alaska |
Swiss and Italian meringues heat the whites enough that they are considered safe to eat without further baking.
Ratios
A large egg white weighs about 30–33 g. For crisp baked meringues, use about twice the whites' weight in sugar, roughly 60 g (1/4 cup plus 1 tbsp) per white. Soft pie meringues can use less, about 25–40 g per white.
Superfine (caster) sugar dissolves fastest. Rub a bit of meringue between your fingers; if it feels gritty, keep whipping.
Peak stages
- Soft peaks: tips flop over when the whisk is lifted.
- Firm peaks: tips bend slightly at the end.
- Stiff peaks: tips stand straight and the meringue is glossy.
- Over-whipped: dry, lumpy, and starts to separate. Folding is difficult.
Baking
Bake crisp meringues at 90–110 °C / 200–225 °F for 1–2 hours, then turn off the oven and let them dry inside. Low heat drives off water without browning the sugar. Higher heat, around 175 °C / 350 °F, is used for browning soft pie toppings quickly.
Troubleshooting
- Weeping: sugar not fully dissolved, or topping a cold filling. Spread pie meringue onto hot filling and seal it to the crust.
- Beading: over-baked; proteins squeezed out syrup.
- Sticky surface: humid day. Store airtight right after cooling.
- Collapsing: under-whipped or folded too roughly.
Questions
What is the difference between French, Swiss, and Italian meringue?
French meringue adds raw sugar to whipped whites and is the lightest but least stable. Swiss meringue heats whites and sugar together to about 71 °C / 160 °F before whipping. Italian meringue streams hot sugar syrup at 118–121 °C / 245–250 °F into whipped whites and is the most stable.
Why won't my egg whites whip into peaks?
Usually a trace of fat: a bit of yolk, an oily bowl, or a plastic bowl with residue. Fat interferes with the proteins forming bubbles. Use a clean glass or metal bowl and separate eggs carefully.
Why is my meringue weeping or beading?
Weeping (liquid at the base) usually means undissolved sugar or under-baking; beading (droplets on top) usually means over-baking. Humidity also makes meringue sticky because sugar is hygroscopic.
How much cream of tartar per egg white?
About 1/8 tsp per large egg white. The mild acid helps the proteins unfold and bond more gently, giving a more stable, finer foam that resists collapsing.