Marshmallow science explained

When I made marshmallows a little while ago I gave you a recipe with some handy tips. However, I didn’t yet get to my favorite pastime, discussing the science behind this great creation! So, are you ready? Here’s marshmallow science explained!marshmallow image

When you study the marshmallow recipe you’ll see that it’s actually simply a stabilized egg foam. It’s been stabilized by heating the eggs and by adding sugar and gelatin.

Stabilizing a marshmallow – trick 1: Sugar

Let’s zoom in on the sugar first, why does this stabilize an egg foam? Well, first of all, the sugar does not interact with the egg proteins themselves. Sugar stabilizes the foam by stabilizing the air bubbles itself!

When you whisk up an egg you’ll create a foam of air bubbles in water. In this water, you’ll have some egg proteins floating around. The reason an egg foam is not stable is because of the air bubbles merging together and raising up. This has to do with several phyiscal phenomena such as surface tension, but let’s not zoom in on that now.

Sugar makes it harder for the air bubbles to merge and for the water to move around. Adding sugar to wate rmakes water more viscous, in other words, it won’t flow that easily. You can tests this easily by dissolves a heap of sugar in some water. Once you’ve dissolved enough, it will become pretty thick.

So sugar simply makes it harder for the air bubbles to move through the water and for the water to move as well!

Kitchen experiment: 

Want to test this? Whip up an egg white without sugar and whip up an egg white with about 50g of sugar. Leave them both to sit on the counter. Which has reduced in size fastest?

Granulated sugar & glucose syrup

There’s a good reason that you should use both granulated sugar and glucose syrup. Granulated sugar is only made up of sucrose molecules. Upon cooling down these tend to crystallize, simply because crystalline sugar is the most stable form of sugar. This can be prevented by either eliminating the amount of water severely (and cool down carefully) or adding something else to inhibit crystallization. Glucose syrup is such a crystallization inhibitor. The syrup contains glucose of course, but also a lot of large carbohydrate molecules. These large molecules sit in the way of the sugar.

roasting marshmallow
Heat doesn’t only stabilize a marshmallow before making, it also make it really nice and soft and gooey.

Stabilizing a marshmallow – trick 2: Heat

Let’s focus on the heat next. As you can see in my infographic on eggs, both whisking and heating eggs will stabilize egg proteins. Whereas whisking only causes a very short stabilization (just leave freshly whisked eggs on your kitchen counter, they’ll ‘unwhisk’ within hours, heat will stabilize them for a longer period of time.

In marshmallows heat is brought in by heating the sugar syrup. This is a great way to combine different functions. On the one hand, the heat of the syrup will cook the egg proteins, firming up the structure. On the other hand it is used to dissolve a large amount of sugar and make sure that the water with sugar dissolved in it is really viscous.

It is very important that you heat the sugar to the right temperature. I’ll write a more extensive blog post about it in the future, but in short it’s this. When you heat a sugar syrup, you evaporate water. The temperature will actually tell you how much water is still in your mix. It is very important to have the right amount of water. If there’s too much, the syrup won’t be thick enough to support the marshmallow. If there’s too little, the sugar will become very hard (like a caramel) and the marshmallow won’t be fluffy, but firm and hard.

3rd stabilizer of marshmallows: Gelatin

Since you use a syrup with still quite a bit of water, the egg foam with syrup structure is not yet stable. That’s the reason gelatin is added. Gelatin molecules (these are also proteins, just like proteins in egg white) will sit in the water phase of the foam. Gelatin is very good in forming a gel. This gel forming property will stabilize the marshmallows further.

Now that you’ve got a recipe and now that you know why you have to make it in this way, you can go ahead in your kitchen! Good luck and let me know what you’re able to make or when you run into problems.

Quick update here, I’ve also tried making marshmallows using marshmallow root instead of gelatin, so real marshmallow marshmallows :-)!

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