Beaten egg whites are the basis of many recipes: angel food cake, meringue, soufflé, mousse, and floating islands… All these mixtures owe their light, ethereal texture to air bubbles trapped inside the egg whites. But they still have to be beaten into those stiff peaks! Did you ever ask yourself how an egg white could have such a light texture? Thanks to its proteins.
Meringue under the microscope
An egg white is composed of water and various proteins. The proteins resemble long, rolled up string. When you whisk an egg white, the quick movement unravels the protein and incorporates air bubbles at the same time.
Air bubbles are large and sparse when you start to beat an egg white, and the foam is still clear and liquid. The more you whisk, the more air bubbles start to form and divide. An egg white turns white because its millions of small bubbles reflect the light. At the same time, long proteins unfold and form a film that coats the air bubbles. Protein and air bubbles also trap water contained in the egg white: this is why it becomes firm.
The texture of shaving cream
For meringue to have maximum volume and stability, you have to beat egg whites until the air bubbles become smaller and the mixture holds well. How do you know if they have been beaten enough? Egg whites should have the smoothness of shaving cream and form peaks when you remove the whisk.
On the other hand, if the whites are beaten too much, proteins will bond together and there won't be enough of them to surround air bubbles. The appearance of the mixture will change: instead of looking soft and foamy, like shaving cream, it will become too hard and look dry. The egg whites will appear grainy.
The result won't be disastrous if you use grainy egg whites in a recipe, but isn't ideal either. Egg whites will expand less during baking as protein molecules have lost their elasticity. Result: cakes and soufflés don't rise as they should. But, all is not lost! To restore the texture of egg whites that have been beaten too long, add one more egg white and start whisking the mixture again. It will regain an almost perfect smoothness.
Make it, Use it
Once egg whites are beaten into meringue, they must be quickly added to a recipe. In fact, the proteins in egg whites continue to bond together even after you have stopped beating them. Water doesn't hold between air bubbles and quickly sinks to the bottom of the bowl. Result: egg whites become dry and hard, as if they have been beaten too long. As we previously explained, add another egg white and whisk the mixture again, as long as it does not have to sit around for more than an hour.
To add or not to add: cream of tartar?
There are two solutions to prevent egg whites from becoming dry and hard: add an acid or sweet ingredient to the mix. Note that adding salt does not help maintain egg whites beaten into peaks.
The most effective acid ingredient is cream of tartar, a white powder by-product of winemaking. In Europe, they prefer to add lemon juice or vinegar to beaten egg whites. This is effective: the acidity in these ingredients prevents protein molecules from attaching to each other. The foam stays smooth a little bit longer. Egg whites beaten into peaks with cream of tartar help cakes and soufflés rise further. It is recommended to add 0.5 ml (1/8 tsp.) of cream of tartar per egg white.
As for sugar, it helps to stabilize egg whites in two ways. Small sugar molecules insert themselves between long protein molecules, preventing the latter from becoming too stuck together. Then, since sugar is hygroscopic (it attracts moisture), it prevents water in the egg whites from sinking to the bottom of the bowl. The amount of sugar needed depends on the recipe.
Types of meringue
Meringue is a mixture of stiffly beaten egg whites and sugar. There are two main types of meringue and three ways to make it. Hard meringue is baked in the oven for a long time at a very low temperature to dry it. It is used to make cookies and desserts like vacherin or pavlova. Soft meringue is light and fluffy. It is baked for a short time in a hot oven. It is used to top pies, such as Christina's lemon-lime meringue pie.
When to add sugar?
Hard meringue contains two times as much sugar as soft meringue. In both cases, the secret to success is to wait to add sugar until the egg whites have risen well and formed soft peaks. In fact, if you add sugar too soon, the meringue will take longer to form stiff peaks… and it will have less volume.
Do egg yolks prevent the whites from rising?
Yes and no. Contrary to popular belief, a bit of egg yolk in a large volume of whites will not prevent them from rising into peaks. You will, however, have to beat the mixture longer. Keep in mind that if there are a lot of yolk drops in the egg whites, it will be difficult to beat them into peaks and they will never become firm. A tip: retrieve egg yolk that fell in the whites using a piece of eggshell. The yolk will stick to the shell and can be easily removed.
A copper bowl gives better results?
Absolutely! Copper helps stabilize the whites, because there is a reaction between the copper bowl and conalbumin, a protein found in eggs. But don't spend a fortune buying a copper bowl… cream of tartar has the same effect at a fraction of the cost.
A perfect meringue pie
Do your meringue pies weep (have drops of liquid on the surface)? Does a layer of water form between the meringue and the filling? Don't worry, there are solutions. These two problems commonly occur when you bake an ordinary meringue pie. Those drops of water on the surface are not caused by humidity, but by excessive baking. Protein on the surface of the meringue coagulates (thickens) too much and expels the water it was holding. Water exits the foam and forms droplets.
Conversely, the layer of water that appears under meringue can be caused by not baking a pie enough. In this case, the inside of the meringue did not reach a temperature high enough to allow proteins to clot.
How to find the middle ground? Browning meringue quickly under the broiler in the oven is not an ideal solution because only the top will bake. This does not solve the problem of that layer of water forming under the meringue. To ensure the underside of meringue bakes as well, it is recommended to spread it on a pie right after the hot filling has been poured. When it comes to the final baking stage in the oven, experts are divided between two techniques that both give a good result:
- Bake at 160 °C (325 °F) for 20 to 25 minutes or until the meringue's peaks are browned. This technique is preferable for pies covered with a meringue made from four or more egg whites.
- Bake at 210 °C (425 °F) for 4 to 6 minutes. This method works better for meringue made from three egg whites or less.
A secret ingredient: corn starch
Here's a great tip for a perfect meringue pie that will not weep on the filling: add corn starch to the meringue. Corn starch is composed of long molecules that it is believed insert themselves between egg white proteins to prevent them from clotting too much while meringue is baking. Corn starch molecules also provide more hold for meringue. It will be easier to cut and is less likely to weep. How? Mix 15 ml (1 tbsp.) of corn starch with 75 ml (1/3 cup) of water and bring to a boil on the stove or in the microwave. Let cool and add to a meringue made from 4 egg whites (or more), after the egg whites have been whipped into peaks. For the complete how-to, consult Christina's lemon-lime meringue pie recipe.
Meringue in the oven as white as snow
Hard meringues are made from ordinary meringue but are baked for hours at a low temperature in the oven (between 95 to 110 °C or 200 to 225 °F). This slow baking is designed to make them crunchy without turning brown. They still end up losing a bit of their whiteness anyway and take on a creamy colour. Why? Because baking, even at 95 °C, is still too hot and causes browning. However, ordinary meringue alone is not stable enough to be baked on low heat in the oven.
The solution is to make hard meringue with Italian meringue. This type of meringue is a lot more stable because it has already been cooked by the hot sugar syrup used to help it rise. All that's left to do is to bake the Italian meringue at the lowest possible temperature. As for my own oven, the lowest temperature is 75 °C (170 °F). I bake meringue in the oven for about four hours, depending on the size. I then let it cool in the oven for several hours or overnight. It stays as white as snow!
Perfect meringue: mission possible
- Use clean utensils with no traces of fat. A little fat will not prevent egg whites from rising, but will prevent them from achieving maximum volume. Glass or metal bowls are preferable to plastic bowls which are often covered with a thin, greasy film.
- Break one egg at a time in a small bowl and make sure there is no yolk in the white before adding it to other whites in the recipe.
- Use room temperature eggs. The egg whites will rise more easily and produce more volume.
- Wait for the foam to reach the soft peak stage before adding sugar. If sugar is added too soon, you will have to whisk a lot longer to obtain a firm meringue and it will have less volume.
- Do not over beat. The whites are ready when the foam forms slightly curved or straight up peaks when raised slowly with a whisk; it reminds you of shaving cream. Overbeaten meringue loses its softness and will not rise as much during baking.
- Use meringue as soon as possible, especially if it contains no sugar or cream of tartar to stabilize it.
- Gently add the meringue to other mixtures, fold it in with a rubber spatula and carefully lift the mass to lose as little air possible.
All about meringue
Soft meringue for pies: requires 30 ml (2 tbsp.) of sugar per egg white.
Hard meringue: requires 60 to 75 ml (1/4 to 1/3 cup) of sugar per egg white.
How to proceed
French meringue (ordinary): Granulated sugar is simply whisked into egg whites. This easy and popular technique results in a light meringue that is not very stable while unbaked.
Swiss meringue: Egg whites and granulated sugar are beaten together over a pan of hot water (bain-marie). You whisk until a temperature of 50 to 55 °C (between 122 and 130 °F) is reached which allows them to partially bake. This technique results in a satiny, fine, relatively stable meringue. It's our grandmothers' famous 7-minute icing.
Italian meringue: Depending on the recipe, a hot syrup sugar (cooked to between 112 à 120 °C or between 236 and 248 °F) is beaten into egg whites. This technique results in a shiny, very fine meringue with lots of volume. It is the most stable of the three because it is baked by the hot syrup. It is often used in recipes that do not require any further baking (butter creams, mousses, marshmallows, iced soufflés…) or to top French meringue pies or other desserts. It is ideal for meringues dried in the oven that stay white after baking…
Step by step: how egg whites rise
Foamy stage: The bubbles are really large; the foam is yellowish, clear and still runny. It's time to add the cream of tartar.
Curved or soft peaks stage: Air bubbles are small, but still visible; egg whites are foamy, white and soft. They form peaks that fall back down when lifting the whisk. The time has come to gradually add sugar.
Firm, straight up peaks stage: Air bubbles are tiny. The meringue is firm, but still soft. It forms peaks that point straight up when lifting the whisk. Now is the time to stop and use the meringue immediately.
Dry foam stage: The meringue has a dry and grainy appearance. It is no longer soft, but too firm. Liquid may have accumulated in the bottom of the bowl. Don't throw it away! Add another egg white and whisk again. The meringue will be nearly as nice as it was before it turned grainy.