Swiss meringue – Science of this pipeable topping

Whenever you add air into your food to create a foam and lighten it up, your main challenge is how to keep that air inside and prevent it from escaping again. In a lot of cases you will handle the foam very carefully as not to lose all the air. However, in some cases you want to pipe the foam onto another component of your food. Putting the foam in a piping bag and squeezing it through though sounds like  a recipe for disaster if you want to keep in the air.

Luckily, there are several ways you can stabilize a foam in such a way that it holds onto the air, but is ‘strong’ enough to be handled quite fiercely. A Swiss meringue is a great example of this. It is an egg white foam with sugar that can stay soft and pipeable for several days.

How Swiss meringue works

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 enough. By adding sugar to the meringue, you stabilize the foam for a longer period of time. The sugar prevents the air from escaping from the meringue too quickly.

In the case of Swiss meringue you first dissolve the sugar completely in the egg whites. This makes a Swiss meringue super smooth, without any graininess. You dissolve the sugar by gently heating the sugar and egg whites together, this doesn’t just help dissolve the sugar. It also helps the egg white proteins to denature slightly which makes the final foam even more stable. The heat keeps the proteins in place.

Swiss vs Italian meringue

An 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, they don’t differ that much.

Piping a Swiss meringue

As we mentioned at the start of this post, you can pipe a Swiss meringue perfectly fine. 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.

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 heat will induce Maillard reactions in the meringue which results in a brownish colour.

If you don’t have a blow torch you can also use the grill function of your oven. Put it at quite a high heat, you want it to brown as quick as possible without heating up the rest of the pie/tart that’s below it. It depends on the quality of your grill whether you can make it a nice brown.

lemon meringue tarts

Making a Swiss meringue – recipe

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lemon meringue tart cut in two

Swiss meringue

  • Author: Science Chef
  • Cook Time: 20 mins
  • Total Time: 20 mins
  • Yield: enough for 6 small pie toppings

Ingredients

  • 2 egg whites (= approx. 55g)
  • 110g sugar*

Instructions

  1. Get a stand mixer ready with the whipping attachment.
  2. Bring a pot of water to the boil.
  3. Take a metal bowl and whisk the egg whites and sugar together loosely.
  4. Place the bowl on the pot with boiling water and, while whisking continuously, but not very vigorously. You just want to make sure it heats evenly. Track the temperature of the sugar and egg white mixture.
  5. Once the mixture has reached 71-75C, take it off the heat and pour it into the bowl of the stand mixer. Whip it up immediately at a high speed until is is very light and fluffy. It should turn a beautiful white colour.
  6. Continue whisking until it has cooled down to room temperature (stop whisking sooner if you see it collapsing again).
  7. When the meringue has cooled down to room temperature you can fill a piping bag with the mixture. This has several advantages, the piping bag prevents the meringue from drying out any further and keeps it nice and soft besides making it easier to decorate something with the meringue without getting sticky fingers.

Notes

* Use twice the weight of the egg whites, if your egg whites are lighter or heavier, adjust the sugar recipe; also, for larger portions, use more egg whites and simply multiply their weight by two to determine the egg white content.

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