baked meringues

The science of meringue: egg whites & sugar

Have some egg whites left from that ice cream or custard recipe you made? Don’t feel like going through all the hassle of making marshmallows? You will then probably end up using it for an egg white omelet, or, meringues! You can use meringues to top off a dessert, or you could just eat them as is. You can make them in all sorts and sizes, crispy or soft and smooth. The basic concept is simple: whip some egg whites and add some sugar.

Meringues are essentially egg white foams. The egg whites are great in holding onto air bubbles and forming a foam, whereas the sugar is there to stabilize it all so it doesn’t collapse again too quickly. There’s some great science involved that will definitely help you make even better and more varied meringues.

What’s a meringue?

Meringues are whipped egg whites with sugar, a sweet egg white foam is what it is. A lot of meringues have received some heat treatment as well, to stabilize them, but you can make a meringue without heat.

Meringues can be used by themselves, as a topping (on pie or eggnog), but can also be part of a dish. You use a meringue to add air to your chocolate mousse for instance. The meringue serves to incorporate some of those desired air bubbles into your mousse.

Types of meringue – French, Italian, Swiss

There are a lot of different types of meringues. A common classification is to group them into French, Italian or Swiss meringue. Whereas the names aren’t always used consistently, these are all descriptors of a meringue that’s been heated. The main distinction is how the heat and sugar are added.

For the French version (in Dutch called schuimpjes) you add sugar to raw whipped egg whites. This mixture isn’t stable over time, so you bake them in the oven (see recipe at the end of this post). This makes them crispy, but still slightly soft on the inside. By heating them and drying them out slowly you can store these for a long period of time as long as you store them in an air tight container.

When making an Italian meringue you first make a hot sugar syrup. You then pour this hot sugar syrup over and through beaten egg whites. The heat of the syrup cooks the egg whites, stabilizing them.

Last but not least, in the so-called Swiss version you gently heat up the egg whites and sugar together while whipping it. Once they’ve reached the temperature you’re aiming for you increase whipping drastically. This meringue definitely isn’t crispy, but it is very light and airy and even stable enough to pass through a piping bag without losing all the air again.

Why egg whites foam so well

A meringue starts with whipping up egg whites. A meringue requires a lot of air bubbles and a light foamy texture. Even if you whip an egg whites with a fork you will see air bubbles popping up. If you’d do this with water you might see some bubbles, but they will disappear again very fast. An egg white foam though can hold on to that air quite long.

What’s going on here?

Egg whites are mostly moisture and proteins, quite a lot (about 10%) of proteins but barely any fat. Egg white contains a mixture of proteins, the most prevalent one being ovalbumin. What’s special about this protein is that it can be denatured (unfolded) quite easily, simply by using some mechanical force (here’s where a whisk comes in play). When a protein denatures it unfolds. Parts of this unfolded protein chain like to sit in water whereas other parts do not (hydrophilic vs. hydrophobic). If at the same time air bubbles are incorporated into the egg white the parts that like to sit in water will sit in water, whereas the parts that do not will try to sit next to the air bubbles. This way the air bubbles are held in place by these unfolded protein chains.

The egg white proteins aren’t strong enough to hold on to the air forever. Over time, the air bubbles will coalesce and the egg white foam will collapse again. This is why a meringue has to be stabilized.

Meringues, ready to go into the oven
Meringues, ready to go into the oven

How sugar stabilizes an egg white foam

If you would try to bake your pure egg white foam, chances are that it will collapse in the oven. The heat of the oven evaporates the water in the foam. This makes it harder for the proteins to keep the air bubbles apart, essential all you’re left with is egg white protein. As a result, the air bubbles will escape and the foam will collapse.

This is why sugar is added to the egg white. Not only does the sugar sweeten the meringue, it has a very important structural role. Its first and foremost job is to help stabilize that egg white foam.

Adding sugar will increase the viscosity of the liquid phase in the egg white. Sugar dissolves in water, and if you dissolve enough it will form a sugar syrup. As you will have probably seen for your self, these sugar syrups tend to be a lot thicker than pure water.

By increasing the viscosity of the water phase, the sugar makes it harder for the air bubbles to merge together and escape. The air has to go through a layer of which the molecules don’t move as freely and don’t let the water through well. If you leave both a whisked egg white with and without sugar on your counter you will find that the sugary mixture stays foamy for a lot longer.

Powdered sugar vs granulated sugar

Depending on the type of meringue you’re making, you might be adding quite a lot of sugar to your meringue. In some recipes the concentration of sugar actually is close to the maximum amount of sugar that can dissolve in water at room temperature.

Since you want to dissolve all this sugar (else it will become gritty) recipes tend to call for using powdered (icing) sugar. The only difference between powdered and granulated sugar is the particle size. That of powdered sugar is a lot smaller and as a result it dissolves a lot more easily.

How egg yolk destabilizes an egg white foam

Before we dive even deeper into the world of meringues, let’s make clear that you really should only use the egg white and not the yolk for making a meringue. A yolk also contains proteins, but apart from that, it contains fat, which egg whites don’t. This fat can ruin your meringue.

As we discussed, proteins stabilize the egg white foam by unfolding and sitting on the surface between water and air. However, if fat is present, these proteins will not just sit on the water/air interface. Instead, it will probably prefer to sit on the fat/water interface, somewhat acting like an emulsifier. This severely limits the foam stabilization properties and as a result your foam won’t be as stable and will collapse a lot more easily.

whipping up Italian meringue

Firm, soft, light or dense meringues

By changing the ratio of sugar to egg white as well as by changing how and when you add the sugar, you can change the structure of your meringue.

There are of course a lot of moments you can add sugar to your egg whites, but there are two extremes: either at the start, before start to whip, or at the end, when you’ve already got your foam.

Generally speaking, adding the sugar at the beginning will give a denser structure. There tend to be more air bubbles, but they’re smaller. Also, it will take a lot longer for the egg white to actually form a foam when the sugar is already there. These types of meringues are sturdy enough to be piped in a piping bag and don’t need as much attention. If there’s plenty of sugar in there you aren’t that much at risk of overbeating the foam.

However, if you add the sugar add the end you’ve already created a very light egg white foam and the sugar will not affect the foam properties that much anymore. Instead, it will just dissolve and help support the egg white. You have to be more careful with this foam and most definitely cannot pipe it, you will push out all the air again.

A crispier French meringue

If you’re baking your meringue in the oven (French meringue style, you can find a recipe further down) the amount of sugar will impact the crunch and crisp of your meringue. More sugar will give a crispier sturdier meringue. This is because the sugar prevents the moisture from evaporating too quickly (so it won’t collapse that easily) but also because sugar itself, together with the protein, will form a sturdy structure that’s the actual meringue.

Once the meringue cools down the sugar will crystallize and the meringue will firm up. Sugar serves a very similar role in cookies, where it also contributes to crispiness.

A recipe for baked meringues (schuimpjes)

This recipe make small meringues that are baked in the oven to create a light crispy texture. It’s a good recipe to start with when developing a crispy meringue. Adding more sugar will make it even more crispy, whereas adding less will make it lighter, but you’ve just learned that, so should be able to figure it out.

Baked meringues / Schuimpjes

Baked meringues / Schuimpjes

Yield: 20 small ones
Prep Time: 15 minutes
Cook Time: 45 minutes
Total Time: 1 hour


  • 2 egg whites
  • 100g sugar (standard)
  • sprinkle of salt
  • vanilla sugar


  1. Whisk the egg whites (easiest is to use a stand mixer) until they've started to form a very soft foam. Add the used, salt and vanilla sugar and keep on whisking until the peaks in your peaks stay up by themselves.
  2. Bake at 100C for 45 minutes or until they're nice and firm. If you bake them too short they will collapse, baking too long will dry them out slightly.

A quick note on lemon juice & cream of tartar

Many recipes will call for using lemon juice or cream of tartar in your meringues. Both of these help stabilize your foam. In a lot of cases you can do without them but it will just give a slightly less stable or less firm foam.

Both work by lowering the pH-value of your egg white mixture. In other words, it makes the meringue mixture more acidic. These lower pH-values help the proteins to unfold and thus helps stabilizing your egg foam even better.

If you’re reading for leveling up your meringue science skills, it’s certainly worthwhile having a go with these two ingredients, but remember, you only need quite little amounts.

Further reading

Effect of sugar, citric acid and egg white type on the microstructural and mechanical properties of meringues, Fabio Licciardello, Pierangelo Frisullo, Janine Laverse, Giuseppe Muratore, Matteo Alessandro Del Nobile, 2011, Journal of food engineering, link

Effects of sucrose and sodium chloride on foaming properties of egg white proteins, Vassilios Raikos, Lydia Campbell, Stephen Euston, 2007, Food Research International, DOI: 10.1016/j.foodres.2006.10.008, link

A Study of the factors affecting the foaming properties of egg white – a review, K. Lomakina, K. Mikova, 2006, Czech J. Food Sci., 24: 110–118., link

Cook’s Illustrated on meringues, visited March-2018

Fine cooking on meringues, visited March-2018

On food and cooking, Harold McGee, 2004, p. 108-110

Exploratorium on egg foams

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  1. I LOVE your Blog Post on Meringues.

    Are you in Holland? Do you often post Dutch Recipes?

    I ask because I am looking for some Dutch Recipes
    and I am not having much luck finding a good Dutch Appelflappen.
    I have an old Dutch Cookbook, and use it for my Oliebollen, But, the Appelflappen
    is just making me a bit lost. 🙂

    I live in Sweden and all the Appelflappen Recipes I am finding call for self-rising flour,
    we don’t have this in Sweden.

    I have noticed that the difference between the Oliebollen, and the Appelflappen
    is that Oliebollen uses yeast, and it seems that Appelflappen uses baking powder.

    anyway, I look forward to reading more of your blog.

    • Hi!
      Thank you for reading my blogpost :-), I haven’t been writing a lot lately, but trying to write some more the coming time.

      Finding an English recipe for appelflappen might indeed be difficult, in my Dutch cookbooks I could find several :-).

      The easy way to make appelflappen is using store bought puff pastry (generally the frozen type). In the Netherlands you can buy this in squares of approx. 15-20 x 15-20 cm. Cut some apples in pieces and mix with sugar and cinnamon (to taste), place some apple mix in one half of the puff pastry and then fold the upper left corner onto the lower right corner to form a triangle. Fix both sides together with a fix and decorate with some egg to get a nice brown crust. Bake the puff pastry according to the instructions of the pack (generally 15-20 min at 200C. This is a method I generally use.

      In one of my recipe books I found a similar method, using either store bought puff pastry or ‘Hollandse korst’, which is a recipe for a Dutch puff pastry. It’s too complicated to completely explain here, but it consists of making a puff pastry dough from 500g flour + 3/4 tsp salt + 500g cold butter + 275 ml water. Cut the butter in cubes and gently mix with water and flour. Then follows a process of folding the dough, resting and cooling it, folding it again, etc. Just like with puff pastry. Once the dough is made they use half this amount for making 8 appelflappen. For eight appelflappen they mix 2 big apples (cut into pieces) + 35g sugar + 1 tsp cinnamon + 1,5 tbsp corn starch (Maizena in Dutch, which is just a little different from corn starch) + 35g raisins. This they use to fill the squares of dough and also coat with egg. It’s baked in the oven at 200C for 15-20 minutes. It’s pretty similar to what I do, feel free to vary quantities etc. to taste.

      Hope this helps :-).

  2. I’ve learned science at school and baking on-the-job in a kitchen but I wish I could’ve studied the science of baking as well! So now I read a lot about the topic to understand what’s happening in my mixing bowls 🙂 I’m glad I found your blog!

  3. Excellent article for those of us who want to dig deeper into the details of things!

    You say, “There are of course a lot of moments you can add sugar to your egg whites, but there are two extremes: either at the start, before start to whip, or at the end, when you’ve already got your foam.”

    Which method is best if I want to pipe bite-sized meringue drops that have chewy interiors?


    • Hi Linda,

      Thanks for that great feedback, very glad to hear it’s helpful. In my experience, both methods should work for small drops. I have not tried all methods myself, but I would suggest you start by adding everything in at the start (simply because it’s way easier!). If that texture isn’t entirely right en you’d like it somewhat smoother, I would suggest trying the other extreme and then based on that, choose which one works best for you!

      Good luck and I’d love to hear what you choose to do!

  4. Hi there, just read through your article trying to troubleshoot something. My daughter and I make macarons using the Italian meringue method. Lately, in our meringues we notice these little strands that feel like plastic. We have noticed them in our meringues using two different types of sugar (Domino and Dixie Crystals), both of which are supposed to be pure enough for merengues. Any ideas what this could be from? We are usually able to see most of them during piping the macarons but of course some sneak through which always is a nice surprise. Thank you for any insights!

    • Hi Katie,

      Thanks for teaching me that you can make macarons using the Italian meringue method! I’ve always made them using the French method, so I’ll need to add the Italian version to my experimentation list!

      But to come back to your challenge, assuming that you don’t actually have plastic in your batter (you’re not heating plastic causing it to melt?), I would expect that these strands are made out of sugar. When you make a hot sugar solution and pour it into a mixer while it’s whipping (which I’m assuming you’re doing) you might swirl some of the hot sugar solution to the side of the bowl where it cools down and forms a firm strand. Even mixing this into the batter again won’t get rid of these, only heat will help them dissolve again. Normally though, these loose strands would be caught onto your bowl and they wouldn’t transfer in your batter that easily. Maybe some of them break apart and do end up there? If this is happening, you should only have a few of them.
      You could solve this by whisking more slowly while adding the sugar syrup, preventing it from spinning to the sides.
      If you want to test whether they are made of sugar, take one of the strands next time you encounter them and place them in some warm water. Heat the water up, if it dissolves quite easily, it’s probably sugar!

      If this can’t be the problem, please tell me more about how you’re making them to see if there’s something else that could be causing this plastic-like strands!

      • Thank you very much! I also reached out to a pastry chef friend of mine and she said basically the same thing: to avoid hitting the whisk when pouring the syrup into the egg whites (this is difficult for me – i will slow the whisk down even more) but also to wait maybe a minute or so after letting the syrup get to temperature before adding it. There should be no plastic coming into contact with anything, so it must be something with the sugar. And we do see them mostly clinging to the wire whisk, and yes there are only a few. If any sneak through my daughter usually catches them when she’s piping the shells.

        We have much more success using Italian meringue with our macarons. In our climate, the french ones are unstable. My oven is old and non-convection, so I can only cook one pan at a time. Even the relatively short time the french method batter was sitting out caused it to do some funky things. We don’t lose any when we do the Italian meringue method.

        Thank you so much for your help and suggestions!

      • Okay more of the same weird meringue adventures. The “plastic” strands are not sugar. They did not dissolve in hot water. We are thinking it’s the eggs cooking?! How would you avoid this? We have the eggs at room temp and we let the syrup sit for about a minute before adding it to the partially whipped whites. Is it possible we’re adding the syrup too quickly? Thanks.

        • Hi Katie,

          The mystery continues! I’m not too sure what’s going on here, it would almost have to be the eggs if it’s not the sugar, there’s not a lot more in there! The proteins in eggs do denature, which is a permanent, irreversible change (unlike the sugar, which should dissolve back in hot water). Are they very sticky? Do they stick to the bowl? Normally, you’d want to pour the sugar quite soon after heating it since cooling down can cause it to solidify and harden. I couldn’t imagine though that leaving it to sit for a little while should make much of a difference, it tends to take me a little while to get everything ready to pour. If anything, I’d think you’d have to pour sooner, not later, but again, can’t see how that one minute should make the difference.

          Could you whip the eggs a little more? Once they’re a foam, they hold together in a different way than when they’re liquid? It’s really just a guess because you’re starting to run out of other options here!

  5. How hot is 100c in ferenhight

  6. I love the baking fundamental posts! So helpful for a newbie like me. I will be looking out for that cake and buttercream recipe!

  7. As soon as I saw this I knew I had to make these- so my son and I made them last night. They’re fantastic!! Delicious and addictive.

  8. I’m trying to make crispy meringue inside and outside. However, my meringue always attracts moisture and becomes sticky and chewy (not what I want at all). I’m using 2 eggs with 80g sugar added gradually and baked at 140 degrees celcius for 1 hour. Kindly advise what I can do to keep the meringue crispy for Long? Thank you!

    • Hi Becky,

      Over time a meringue will always become softer, especially if you live in a humid climate. If your meringue is crunchy when it comes out of the oven, cool it down, and once it’s at room temperature, store in an air-tight container. This will prevent extra moisture from coming in and softening the meringues. If you use meringues on pies etc. they’ll become soft over time as well, it’s the migration of moisture and that’s hard to stop! Your best bet here is to add them as late as possible.

      If your meringue doesn’t get crispy at all, try baking it for longer at a lower temperature (so it doesn’t brown/burn) to dry it out even more. The drier the crispier!

      Hope that helps!

  9. A step in the right direction is to have your stainless steel bowl & beater COLD! When trying to whip up anything, be it egg whites, whipping cream, heavy cream, etc, it helps if you have your utensils cold.

  10. This is the most Informative information I’ve ever seen on eggs and sugar. This better comprehension will without doubt aid in my future experiences. Thank you ever so much.

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