Meringue: The Science Behind a Wonderfully Fluffy Dessert

What’s your favourite part of a meal? Some people would say dessert. How about you?

Have you ever indulged in a piece of lemon meringue pie or pavlova? Both of these are meringue-based desserts. Meringue is a fluffy mixture that is delicious on its own. It is also used to give mousses, macarons, and some buttercream frostings their light and fluffy textures.

If you’ve never made meringue yourself, you might be surprised to learn that the main ingredients are simply egg whites and sugar! Let’s have a look at the science behind transforming egg whites into fluffy clouds of tastiness.

Proteins and amino acids in egg whites

An egg white is about 90% water. The rest is almost all protein, with traces of minerals and vitamins. The cells of all living things contain proteins. For example, skin, muscle, feathers, and egg whites all have proteins in them.

Proteins are made up of long chains of hundreds or thousands of molecules called amino acids.

There are about 20 common amino acids. However, they can be combined in many different ways to produce proteins that can build anything from the lens of your eye to a spider’s web to an egg white.

The order of amino acids in a protein cause it to fold up into a blob-like structure, a bit like a ball of yarn. Some amino acids are hydrophobic (water-fearing). Instead of dissolving in water, they clump together. Others are hydrophilic (water-loving). They are attracted to water. Proteins that usually make their home in water fold up so that most of the hydrophilic amino acids are on the outside of the blob and the hydrophobic amino acids are hidden away inside the blob. 

Did you know?

One of the most common allergies among humans is an allergy to eggs.

What happens to proteins and amino acids when you make meringue?

When you whisk egg whites, you create foam by adding air, which creates bubbles. At the same time, the wires of the whisk cause some of the proteins to unravel. This is called unfolding or denaturing. 

Did you know? 

Egg whites can increase six to eight times in volume when they are whipped!

Denaturing exposes some of the hydrophobic amino acids, which move to the air bubbles to get away from the water in the egg white. As proteins coat the air bubbles, the hydrophobic amino acids begin to react with each other. This causes them to link together to form nets, which can help keep the bubbles from popping.

Denaturing can also happen chemically if you add an acid, like lemon juice or cream of tartar, to the mixture.

What is the science of sugar in meringue?

The protein-wrapped bubbles you just learned about cannot stand on their own. Something else must be added to the foam to help keep it together. This is where the other key ingredient of meringue comes in: Sugar! 

Adding sugar to foamy egg whites creates a thick and glossy foam. This foam remains even after you stop whisking. Food scientists believe that sugar helps more proteins gather on the surface of the air bubbles, making the bubbles even more stable.

Did you know? 

Chefs also like to add acids while making a meringue to increase the amount of bubbles that it can hold, so that the meringue will become much lighter and fluffier!

Meringue pro tips

You need to be careful when separating the egg white from the egg yolk. Yolks contain fat molecules, which are also attracted to air bubbles and push some of the proteins away from them. But unlike proteins, fat molecules do not help stabilize the air bubbles. Instead, they cause them to pop, making it difficult to make meringue. Other fats, such as cooking oil and butter, will have the same effect. So it is important to make sure your whisk and bowl are spotlessly clean!

It is also possible to whisk a meringue too much. If you do, it will eventually split into a grainy solid and a runny liquid. This happens when too many proteins join together and form a net that is so tight that it starts to squeeze the water out of the egg white.

You can help prevent over-whisking by stabilizing the mixture. The acid that you may have added earlier in the process to denature the proteins, can also help stabilize your meringue. Acids will prevent too many proteins from linking together so the protein nets do not become too tight. Another option is to make the meringue in a copper bowl. Small amounts of copper ions (charged copper molecules) from the bowl will also prevent too many proteins from linking together. 

Did you know? 

Plastic bowls may hold trace amounts of oil from previous uses, which is why chefs will choose metal bowls when making meringue!

Now that you know the science behind meringue, why not head into the kitchen and make some yourself? 

Cooks have many superstitions about how to make the fluffiest meringue. For example, they might insist on cold or room temperature eggs, older or fresher eggs, or adding in sugar at different stages of the whipping process. Try putting these superstitions to the test and see they actually make a difference!