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It is super easy to whip up egg whites and create a light and foamy consistency. The tricky bit though, is to ensure that the air stays inside and doesn’t deflate out again! This is a common challenge, whenever you add air into your food, whether it’s whipped cream, a meringue or a mousse.
It becomes even more challenging when you want to make a topping for a pie or cake that you deposit using a piping bag. During piping you press considerably on the foam, risking getting rid of all of that air again! So you need to stabilize the foam enough for it to handle all this force. A Swiss meringue, one of many types of meringue, does just that.
Holding on to air
There are several strategies to keep air in your food. For one, you can add an ingredient that solidifies and stabilizes the foam. This is what the chocolate in a chocolate mousse does. Another alternative is to dry out the foam, which makes it solid. This is what you do when making a French meringue. Another option is to handle the foam very carefully, but this is not really an option when you want to pipe the foam on top of your pie.
A Swiss meringue uses other strategies to stabilize the air.
How Swiss meringue works
The thing that sets a Swiss meringue apart from other meringues is how you heat it. A Swiss meringue is made from just sugar and egg whites, no additional water. You whip the egg whites and sugar and then heat it up above the pan of boiling water until it is at least 71C. It’s this heat that sets Swiss meringue apart from the rest.
It starts with the egg whites
Like any meringue, Swiss meringue gets its airiness from the whipped up egg whites. The proteins in egg whites are very good in holding onto air once they’ve been whipped up. The proteins unfold because of the whisking and position themselves around the air bubbles to keep them in place.
When you whip the egg whites you create air pockets which are surrounded by the egg white liquid, which is mostly water. By adding sugar to the meringue, you increase the viscosity (aka make it thicker) of that water in between the air bubbles. This prevents the air from escaping from the meringue too quickly.
Then the heat kicks in
By heating up the egg whites & sugar you accomplish a few things. First of all, the increased heat helps to dissolve all that sugar in the egg whites. At a higher temperature, more sugar dissolves in water, which makes a super smooth meringue, you don’t want any crunchy sugar left.
The heat does more though, it helps the egg white proteins unfold. As a result, it can stabilize the foam better. The heat doesn’t fully denature the egg whites, it’s not hot enough for that, but definitely helps it to stabilize the foam as a whole.
Making a buttercream version
Whereas you can use Swiss meringue as is, you can also use it to make Swiss meringue buttercream. Over time Swiss meringue might soften and collapse slightly. Adding butter enriches the Swiss meringue and firms it up, preventing it from collapsing!
Swiss meringue is stable
Because of the combination of egg whites + sugar + gentle heat you create a very stable foam. The air bubbles in this foam aren’t very large, but they are very stable. As a result, a Swiss meringue can handle quite a bit. You can pipe it through a piping bag. It has gained enough strength to withstand the forces you exert on it while piping. It sometimes even looks a bit like a marshmallow (but more sticky and soft), which can also be piped before it’s dried.
There are a lot of different types of meringues. The Swiss meringue is most suitable for piping and dosing onto a pie or other baked good. The French meringue on the other hand is crispy crunchy, better suited for a Pavlova.
The Italian meringue is very similar to a Swiss meringue, however, instead of gently heating the egg whites and sugar together, you actually create a separate hot sugar syrup. You then pour the sugar syrup with the whipped egg whites. This adds even more heat and stability to the meringue and creates a slightly different texture, although, this one is probably most similar to the Swiss version.
It’s the heat treatment that sets them apart and creates those very different challenges!
Browning Swiss meringue
Swiss meringue is perfect to top a pie and you can make it even more spectacular by blow torching the top. The reason they brown so beautifully is the large amount of sugars & proteins. These two are necessary for the Maillard reaction (a browning reaction) to occur. The heat will induce Maillard reactions in the meringue which results in a brownish colour.
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