Learn the science behind:
Italian Meringue – How a Hot Sugar Syrup Stabilizes an Egg White Foam
Wondering what that luscious, bright white, glossy, foamy topping is on top of your pastry? Chances are, it’s an Italian meringue, made by whipping egg whites and mixing in a hot sugar syrup.
Italian meringue is a very stable type of meringue. One that remains light and airy for several days, but isn’t crunchy like a French meringue would be. As long as you have some electrical whisking power to help you, making this style of meringue is a breeze.
- Italian meringue is egg whites + sugar
- What happens when you make Italian meringue
- Troubleshooting Italian meringue
Italian meringue is egg whites + sugar
Italian meringue is made out of just two components: sugar & egg whites. As such, the key to an Italian meringue is not the ingredients themselves, it’s how you bring them together.
To make an Italian meringue you start by whisking egg whites into a light and airy foam. In the meantime, you add a little water to your sugar and bring the sugar solution to a boil. You add that hot sugar syrup to the egg whites to stabilize and set the egg whites into that fluffy foam. As a result, Italian meringue is:
- Super smooth: no sugar crystals to mess up the texture
- Stable: the heat of the sugar syrup ‘cooks’ the egg whites, causing them to hold onto their shape
- Glossy: thanks to the smoothness
What happens when you make Italian meringue
Let’s have a closer look at what happens in each step to understand why this style of meringue is so stable and glossy.
Step 1 – Whisking egg whites
First up, you beat the egg whites until they are light and fluffy. Egg whites is what make this style of meringue possible. Egg whites have this amazing ability to hold onto tiny air bubbles and form a foam, thanks to its proteins. However, egg whites don’t taste like anything, nor are egg white foams very stable. Within a few hours they’ll collapse.
Adding some sugar for stability
To start improving the stability of the egg white, and to help it form an even airier foam you add some icing sugar at this point. Icing sugar dissolves well in water and so it won’t make the meringue grainy. By dissolving in the water of the egg whites, the sugar makes it harder for the water to seep out of the foam. The sugar ‘binds’ water molecules.
Step 2 – Cooking a sugar syrup
A whipped egg white is not particularly stable. However, the egg proteins can be ‘cooked’. Once cooked, they are fixed in place and the foam won’t collapse as quickly any more. Cooking can be done in several was. The meringue as a whole can be baked in the oven, as is done for a French meringue. Or, the egg + sugar can be heated above a pot of hot water, as is done for a Swiss meringue. In the case of Italian meringue though, the heat is added in the form of a hot sugar syrup.
The hot sugar syrup does a few things to the meringue:
- Cook the proteins: it ‘cooks’ the proteins, stabilizing the meringue
- Increase the viscosity: the sugar syrup is quite viscous and helps to ‘thicken’ the meringue, making it even more stable
- Kill of (some) microorganisms: the heat from the syrup can kill of microorganisms, whether it kills all and truly serves as a pasteurization step depends on the exact quantities and temperature you’re using
An added benefit of using a sugar syrup is that it only contains dissolved sugar, no sugar crystals. The dissolved sugar ensures that the meringue doesn’t turn grainy.
To make this sugar syrup you bring white sugar with some added water to a boil. The sugar dissolves and all the sugar crystals disappear. You then continue cooking until the temperature of the sugar solution has reached a given temperature, in our case 121°C (250°F).
Maintaining the exact given temperature is crucial. The temperature of a boiling sugar solution is a measure for how concentrated that solution is. The higher the temperature, the higher the concentration of sugar. This again results in a different behavior of the syrup, which is referred to when using terms such as ‘soft ball stage’ in candy making.
Boil your sugar syrup for too long and you’ve evaporated so much water that the final meringue becomes hard and chewy. Didn’t boil it long enough and your meringue will not be stable and collapse due to the excess moisture.
This principle of boiling point being related to sugar concentration is crucial for candy making in general. Nougat, marshmallows, honeycomb, they all only work if the sugar syrup was cooked to the correct temperature.
Step 3 – Combine
The final step is to combine the whipped egg whites with the hot sugar syrup. This needs to be done immediately after the sugar syrup has been cooked. Do not leave the sugar syrup to cool down. The syrup will become thick and viscous and it will be hard to take it out of the pan. Moreover, you need the heat to cook the egg whites!
Tip: when adding a hot sugar syrup to egg whites you want to make sure the syrup mixes through properly, without splashing. It’s why it’s best to add the syrup to the egg whites while slowly whipping the egg whites. For homecooks this is easiest to do in a stand mixer.
Step 4: Using Italian meringue
Italian meringue sets over time. It is very flexible and easy to use while it’s still warm. However, once it cools down completely, it can’t be moved nicely anymore. As such, it’s best to use the Italian meringue immediately. It’s easiest to use when it is still slightly warm. It should have lost most of its heat or else it might still collapse slightly and cause other components to melt.
Troubleshooting Italian meringue
Of course, things can still go wrong, but fear not, let’s try to fix it.
The meringue is too firm I can’t spread it!
Three things might have happened here:
- You cooked your sugar syrup to a too high a temperature. This caused too much moisture to evaporate and the overall meringue to become too firm.
- You cooled the meringue down too much. It can become quite sturdy. As you see on the photo below, our meringue had firmed up quite a bit before applying it on our pie, it caused those large air pockets at the bottom.
- Your sugar syrup:egg white ratio is off. Try adding more sugar syrup if the meringue doesn’t flow well, ‘regular’ meringue tends to break easier and not flow as well.
Can I overwhip the egg whites?
Yes, and no. It is possible to overbeat the egg whites in step 1, before adding the hot sugar syrup. However, keep in mind that during this step it is not crucial to whip the egg whites as much as possible. Instead, as you can see in the video, a light airy foam is good enough.
Once you’ve added the hot sugar syrup it is very hard to overbeat the egg whites. You can pretty much continue whisking on a high speed while it’s cooling down without any disastrous effect. This is most likely do to the fact that the proteins have been ‘cooked’ and thus changed texture slightly.
A note on terminology
Is Italian meringue truly from Italy? It’s hard to say, just as it’s hard to say whether French and Swiss meringues are truly French and Swiss. Nowadays meringue made with a hot sugar syrup and egg whites, is generally referred to as Italian meringue in the English language. Depending on where you live terminology might be different. For instance, in Dutch, this style of meringue is also referred to as ‘kookschuim’ (literally translated: “cooked meringue”).