The Science Behind: Meringue

For all my non-bakers out there who are probably very confused right now, meringue is a light and fluffy substance mainly made of egg whites. It is often used in macarons and cakes to add fluffiness or is put on pies because why not? And, like all things in baking, science plays a major role in its creation.

The most familiar baked good with meringue is probably lemon meringue pie (Image Credit: Food.com).

Egg whites are 90 percent water. The remaining 10 percent of the egg white is almost all protein, with trace amounts of vitamins and minerals. Proteins are long chains of hundreds or thousands of amino acids. These amino acids combine in different ways to produce proteins that build things, like eyeballs, spider webs, and, of course, eggs.

Like cats, some amino acids are hydrophobic (they hate water) and others are hydrophilic (they love water) (Image Credit: Giphy).

Before beginning to make meringue, you have two choices. You can use either room-temperature eggs or cold eggs. Cold eggs will be easier to separate and be more stable. However, room-temperature eggs will result in a lighter meringue and turn into meringue faster.

When an egg white is warm, its proteins can move more and have already started the process to become meringue. This leads to warm egg whites becoming larger faster when beaten (Image Credit: Giphy).

But be careful when you separate your eggs! Egg yolks contain fat. You must avoid letting any fat into your egg whites since the smallest fleck of it could destroy your glorious meringue. As you beat egg whites, bubbles form, and if there is any excess fat, the bubbles will pop.

Apart from carefully separating your eggs, don’t touch the egg whites either. Humans are always so greasy (Image Credit: Giphy).

When it’s time to choose a bowl, please don’t grab a plastic one. Plastic bowls tend to retain oils, which, as fats, can screw up your meringue. Instead, go for a glass, metal, or — best of all — copper one. The copper ions in a copper bowl react with the egg whites to lead to a fluffier, more stable meringue.

When making meringue, it’s best to use a powerful mixer and a whisk with many tines — tines are the metal wire-thingys on a whisk (Image Credit: KitchenAid).

When you beat egg whites, you disrupt them, and this causes their proteins to denature — or unfurl — and expand to take up more space. As this happens, the hydrophobic and hydrophilic amino acids are exposed. To reach the compound they prefer and escape those they hate, the amino acids scramble through the egg white. This incorporates air into the structure as the hydrophobic amino acids protect their love: air. To keep their sweetheart close, they coat the air bubbles and link together with other couples to form nets and prevent popping.

Making meringue also requires patience since — depending on the number of eggs — it can take a while for it to form stiff peaks (Image Credit: Tenor).

To help the star-crossed lovers, add sugar and stabilizers when the egg whites start to look light and foamy. Sugar helps more amino acids gather on the surface of the air bubbles, leading to a more stable meringue and adding flavor. Stabilizers, such as vinegar, lemon juice, and cream of tartar, encourage the amino acids to bond together, making the meringue stronger and less likely to deflate. They do this by donating positively-charged hydrogen ions to the egg white’s negatively-charged protein strands, which neutralizes the meringue. This slows down the time it takes for the egg whites’ proteins to denature and allows you to incorporate more air before the meringue becomes over-beaten.

The best sugar to use is superfine sugar since it dissolves quickly (Image Credit: Instructables).

There is one major way to screw up meringue: over-beating. Over-beating happens when too many amino acids join and form a super-tight net. When the net is too tight, the water in the meringue is squeezed out, and your masterpiece is transformed into a grainy solid and runny liquid. But don’t worry! To save your masterpiece, add another egg white.

For most recipes, egg whites should be beaten until they form stiff peaks, as shown on the left. The image on the right is what over-beaten egg whites look like. Please, never let it come to this. (Image Credit: Special Fork Blog and Serious Eats).

Before you begin making meringue, remember: avoid letting in any fat, beat it up well, add sugar and stabilizers, and, most importantly, don’t overdo it. Have fun baking!

Works Cited

Collins, Claire. “Kitchen Science: the chemistry behind amazing meringue and perfect cappuccino.” The Conversation, 8 Dec. 2016, theconversation.com/kitchen-science-the-chemistry-behind-amazing-meringue-and-perfect-cappuccino-64670. Accessed 30 Aug. 2017.

“Meringue: Guaranteeing Success.” Martha Stewart, www.marthastewart.com/266449/meringue-guaranteeing-success. Accessed 30 Aug. 2017.

Rhodes, Jesse. “Meringue Chemistry: The Secrets of Fluff.” Smithsonian.com, 20 Jan. 2012, www.smithsonianmag.com/arts-culture/meringue-chemistry-the-secrets-of-fluff-23039746/. Accessed 30 Aug. 2017.

Wong, Edwin W. Y. “Meringue: The Science Behind a Wonderfully Fluffy Dessert.” Curiocity, 13 Aug. 2015, explorecuriocity.org/Explore/ArticleId/3748/meringue-the-science-behind-a-wonderfully-fluffy-dessert-3748.aspx. Accessed 30 Aug. 2017.

— Isabella S., Pennsylvania

+++

Be a part of our conversation: on Twitter @ScienceTeens; on Instagram at scienceteens; and on Snapchat at march4science.