A marshmallow has a texture wholly unlike any other candy. Squishy, fluffy, and chewy, they will happily float atop a cup of cocoa yet melt and turn gooey and crispy when heated or toasted over a campfire. How is this possible? It's all because of what marshmallows are made of.
What Are Marshmallows?
Marshmallows are made of sugar and corn syrup, and, whether they're made at a candy factory or you make them at home, they also contain gelatin. But the key ingredient is whipped air.
Air isn't typically considered an ingredient, but with marshmallows and other items like whipped cream, meringue, angel food cake, and even scrambled eggs, whipped air is the component that makes the texture of a marshmallow possible.
How Are Marshmallows Made?
The process for making marshmallows involves combining sugar, corn syrup, and water and then bringing that mixture to a boil. The sugar syrup makes the marshmallows sweet and, when heated to a specific temperature, helps give them their texture. After adding gelatin, the concoction is then whipped which incorporates air. Gelatin makes the marshmallows set up and keep their chewy structure. If any additional flavorings or colorings are to be added, as in the case of Marshmallow Peeps, this is the point where that happens.
Candy manufacturers use extruding machines to force that whipped marshmallow mixture through long tubes under extremely high pressure. This process squeezes out thick ropes of marshmallow, which are then sliced into squishy little cylindrical sections. The individual marshmallows then undergo a dusting of cornstarch to help prevent them from sticking together, whereupon they're sealed into bags and shipped to stores.
Note that this process is significantly different from how marshmallows were made up until the 1950s, which is when the extruding machines were invented. Before that, marshmallows were made by hand, which, in addition to being labor-intensive, took quite a bit longer owing to the fact that the individual marshmallows required several hours of "sweating" in order for them to form their outer skin.
Additionally, it was only with the advent of the extruding machines, which operate under high pressure, that marshmallows could be pumped so full of air. Before that, they were decidedly less fluffy. And, unlike today, back then they were made with egg whites so that they would hold their shape better.
How Are Marshmallow Peeps Made?
Marshmallow Peeps are manufactured at a factory in Bethlehem, PA, that turns out more than 5 million Peeps per day. Back in the 1950s, Peeps were made by hand by squeezing the marshmallow creme mixture through pastry bags onto a bed of colored sugar—which is how you would do it if you were making your own homemade Peeps.
It's a two-step process, where first the bases were piped out, using a quick pull-away at the end to form the tail, followed by another dollop on top to form the body and head, again, with a quick pull-away of the pastry tip to form the beak. This all needs to be done fairly quickly, or else the marshmallow creme would harden in the pastry bag. The same goes for covering the Peeps with colored sugar: once the marshmallow sets, the sugar won't stick. Finally, the eyes were dotted on by hand. All of this is done by machine now.
Making Your Own Marshmallows
By contrast, making your own marshmallows is a snap. First, you cook up a mixture of sugar, salt, water, and corn syrup and combine it with gelatin before whipping it in a stand mixer until it's light and fluffy. After dusting a baking dish with powdered sugar, pour the mixture into your prepared baking dish, and then dust the top of the marshmallow with sugar as well.
After it sets, simply turn out the slab onto a cutting board and cut them into squares. Note that once they're cut, the cut sides stay sticky. You can decorate them with sprinkles, dip them in melted chocolate, or just enjoy them as they are.
How Long Will Marshmallows Last?
Marshmallows don't require refrigeration or freezing. As long as you keep them in an airtight container or bag in a cool place, they'll stay good for several weeks and even months. Eventually, homemade and storebought marshmallows will start to dry out. While still edible, they won't have that signature fluffy texture.