The Science Behind Dalgona Coffee

When most of us stayed indoors during the peak of the coronavirus pandemic, there were many reasons to be unhappy, but for those of us who enjoyed the extra time in the kitchen, there were also many reasons to be grateful, including the opportunity to expand our cooking repertoire.

One of the first dishes that eventually became a social media sensation was dalgona coffee, the Korean whipped drink that may have been unfamiliar to us, but is enjoyed in other food cultures such as Greece and India, where it is known as “frappa” and “beaten coffee,” respectively.

Joanie Tian, the chemistry editor at Science Borealis, couldn’t figure out why or how just three ingredients — instant coffee, sugar, and water — could froth up and produce such an Instagram-worthy beverage, especially considering that sugar and water aren’t typically known for their ability to foam. Notably, she discovered that the type of coffee used to prepare dalgona was significant, as the cheaper the coffee, the more foam could be produced.

Tian discovered that there were two types of coffee during her research: spray-dried and freeze-dried coffee. Spray-drying involves making coffee and then drying it to create a powdered concentrate, whereas freeze-drying is a more complex procedure that preserves not only more flavour molecules but also the coffee’s oils. According to Tian, the reason cheaper spray-dried coffee foams so well is because it lacks oils.

In addition to knowing which instant coffee to use, what exactly occurs when coffee, sugar, and water are combined to make dalgona coffee?

Popular Mechanics contacted Spring Arbor University professor of chemistry Tom Kuntzleman for a dalgona explanation. Kuntzleman explained that the reason instant coffee, sugar, and water become dalgona (which means “honeycomb toffee” in Korean, according to the “Today” show) is similar to the process used to make meringue, which requires egg whites to be beaten at a very high speed.

Equipment must be dry and there must be no egg yolk present to contaminate the whites in order to make meringue; otherwise, the science will not work. The egg white consists of 90% water and 10% protein. According to the Exploratorium, whipping egg whites introduces air into the mixture, and as bubbles form, the egg proteins coat the bubbles and separate the water molecules, allowing the bubbles to remain intact for a longer period of time. The water molecules form a bubble film as opposed to bonded H2O, which, as we know, does not foam (but pop).

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