Why Instant Coffee Foams: The Science Behind Dalgona Coffee

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One of the few good things that came from the COVID-19 pandemic was the popularity of dalgona coffee in America. Named after a burnt-sugar Korean candy that was, coincidentally, glimpsed in various episodes of the hit T.V. show "Squid Game," dalgona coffee consists of a thick head of whipped coffee and sugar foam floating atop a mug of milk. It's not only ultra-aesthetic for social media, but it could be an even better way to upgrade cheap coffee than our favorite two-ingredient salt-and-cinnamon trick.

If you are a science-y type who wonders how dalgona coffee works, wonder no more. Basically, the foam on this coffee, like all foams, consists of air whipped vigorously into a medium. In this case, the medium is fresh coffee. In this coffee, melanoidins, or foaming agents, are activated by whipping. Meanwhile, the sugar increases the brew's viscosity, leading to a foam that's especially stable and maintains its peaky shape. 

Instant coffee is the perfect coffee for making foam because it's not as high-quality as other brews, which you know if you've had the ingredients in instant coffee explained to you. Dehydrated coffee, which is the essence of what instant coffee is, happens to be low in foam-disrupting coffee oils, unlike rich, expensive blends. This means that it whips up well. And, once again, no, you can't substitute coffee grounds for instant coffee. Don't be afraid to grab the cheap stuff off the shelf, as it will likely make superb dalgona coffee.

Your gorgeous cup of dalgona coffee starts with a 1:1 ratio of coffee to water, making it scalable. Don't forget to add the sugar before you start whipping, as coffee by itself doesn't have enough surfactants to create good, strong foam. The sugar isn't just for taste; it's also for structure. While whipping by hand with a whisk is definitely possible with enough elbow grease, your coffee will come together much more quickly with a milk frother ... or, better yet, a hand mixer. We've even heard of folks making dalgona coffee for the family using their stand mixers to whip up the foam in record time, although this might be overkill if you are making a solo serving.

Regardless of your mixing tool, whip the coffee-water-sugar mixture until you have a puffy, thick foam with stiff peaks. Take the cup or mug of your choice, add your preferred milk product to fill the vessel halfway, and spoon a heavy, downy layer of foam on top. Snap as many pictures as you'd like, but remember to mix the foam into the milk before consuming. You'll lose the aesthetic value, but the coffee will be delicious. 

If you like a stronger kick with your coffee, you can swap instant espresso granules for your instant coffee. On the other hand, if you are watching your caffeine consumption but still want a refreshing sip, feel free to use decaf, as some social media denizens have done. Caffeine content doesn't affect the whipping process.