But aside from knowing what instant coffee to use, what exactly is happening with the coffee, sugar, and water to make dalgona coffee possible?
Popular Mechanics reached out to professor of chemistry Tom Kuntzleman of Spring Arbor University for a dalgona explanation; Kuntzleman explained the reason instant coffee, sugar, and water becomes dalgona (which means “honeycomb toffee” in Korean, per the “Today” show) is similar to the process used to make meringue, which calls for egg whites to be whipped at very high speed.
In order to make meringue, equipment must be dry and there cannot be any egg yolk present to contaminate the whites, otherwise the science won’t work. An egg white is 90% water and 10% protein. Per the Exploratorium, whipping up egg whites introduces air into the mixture and ultimately, as bubbles form, the egg proteins coat the bubbles and create separation of the water molecules, allowing the bubbles to stay intact for longer. The water molecules, meanwhile, turn into a bubble film versus bonded H2O, which as we know, doesn’t foam (but pop).
Popular Mechanics explains the dalgona mix has a similar composition of proteins, fiber, and minerals, and a very small amount of fat (especially when using spray-dried instant coffee and its lack of oils), which allows it to foam up; further, dalgona’s sugar acts as a glue that holds the foam together, keeping the mix light and airy.
Professor Kuntzleman also successfully made dalgona using salt instead of sugar; however, we don’t imagine it’s something you’d want to try, unless you had no plans of drinking the dalgona coffee, that is.