If you had to describe a marshmallow to a food scientist you would probably say that it is just a foam that is stabilised with gelatin. You see, making a marshmallow is quite simple; you will only need sugar, corn syrup, gelatin, and – something essential: air.
How to make a marshmallow: Gelatin
Gelatin is probably the most essential part of a marshmallow. It is what builds the scaffolding that keeps all the sugar and flavour in place; gelatin can give the marshmallow its stretchy, gooey texture.
To make gelatin, you would need to break down collagen – which is the main connective material in animal tissues – into smaller protein molecules.
When making marshmallows, you start by mixing gelatin with warm water. As the gelatin’s helices unravel from the heat, the protein strands spread out in the water. When the water cools, the junction zones of the gelatin molecules rewind together into a helix conformation.
The gelatin, however, doesn’t always rewind together; its elasticity comes from this mix of bendy and firm components, which is excellent for making marshmallows.
Another advantageous property of gelatin is that it forms a thermo-reversible gel. This means that it can switch between its liquid form and gel form according to the working temperature. Gelatin melts around 35 Celsius degrees, slightly below body temperature; you can then understand its contribution to the marshmallow’s melting property.
In place of gelatin, vegan marshmallows use soy protein and carrageenan. Seaweed’s carrageenan consists of polysaccharides arranged in helices, but it’s not as firm as gelatin. Combined with soy protein, it gives animal-free marshmallows a bouncy texture like gelatin-based ones.
Making a marshmallow involves whipping air into the gel between the melting and solidifying stages so that the gel can properly entrap air into 3D network made of gelatin or vegan alternative. You should whip the mixture just above the gelatin’s melting point, then let it cool and solidify below the gel point. What will happen is that the solidified gelatin matrix will retain the air whipped into it, thus allowing the marshmallow to be puffy and soft. While air is essential to the fluffiness of the marshmallow, it is not the only thing trapped inside that matrix. It wouldn’t be a treat without the sweet stuff, specifically sugar and corn syrup.
The two sweeteners are not the same. Sugar, also known as sucrose, is a disaccharide made of one glucose and one fructose molecule. Corn syrup is a water-based mixture of the sugars dextrin, maltose, and dextrose.
Corn syrup does not crystallise like sugar and reduces the amount of dissolved sugar that crystallises. If you made a marshmallow only with corn syrup, it would be much less sweet because corn syrup is not as sweet as sugar. Corn syrup and sucrose can help provide a range of textures from chewy to tender.
Because the syrup can keep the sugar from crystallising, the amount of each sweetener you use can make or break the texture of the marshmallow. Sugar crystals cause confectionery products to be more brittle than stretchy.
The ratio of sucrose to corn syrup can explain the difference in texture of the many marshmallows formulations that we can find in the supermarket.
I think that now the only thing left to do is go around the supermarket and try different textures of marshmallows or better…have a go and make some at home!