- Whipped coffee (Dalgona coffee) is a viral recipe combining instant coffee crystals, sugar, and water.
- Even traditionally brewed coffee is not well understood, and this whipped coffee seems to work by magic.
- The viral whipped coffee is named for the Korean term for a confection also known as honeycomb.
Whipped coffee, or Dalgona coffee, is a three-ingredient recipe named for a Korean confection that has gone wildly viral in the last few weeks.
The whipped coffee trend began on TikTok and has made it to the Instagram accounts of everyone you know, including celebrities like comedian Chelsea Peretti. Her description of the whipped coffee summed up the timely appeal: It’s “exciting since I no longer go out for coffee or anything really at all.”
Making whipped coffee is simple. The recipe is one part instant coffee crystals, one part sugar, and one part water, whisked or beaten until it forms a rich foam. Last week, someone told me the sugar was optional, so I made the whipped coffee with Splenda, the only sweetener I had in the house. A few days later, I repeated the experiment with sugar, and it worked much better and much faster.
That’s when I thought of chemist Tom Kuntzleman’s Diet co*ke experiments.
Soda with sugar foams differently than soda without sugar, and that’s because sugar acts in a way that prevents bubbles from coalescing. Bubbles stay smaller and separated, which means that while a diet soda might generate more volume of foam right away, a sugar soda has foam that lasts longer. I’d noticed a difference between my “sugar free” and regular dalgona coffee tries. Could this be related to diet soda?
Kuntzleman had theories and ideas right away. He tried regular ground coffee and cocoa powder at first, before he could get some instant coffee crystals. Ground coffee will never dissolve into a liquid, but perhaps more importantly in this experiment, it has an amount of fatty oil that I think could inhibit the formation of foam no matter what. The same is true for cocoa powder, which is hydrophobic, meaning it resists mixing with water at all.
When Kuntzleman was able to try the real thing, he combined the instant crystals, sugar, and water, and sent me a photo of some Instagram-ready foamy whipped coffee. He tried with just crystals and water and, like me, got a much more “watery”-looking and transient foam. Then—this is why you ask a scientist!—he made some using salt with the coffee crystals. It turned out almost as good as the version with sugar.
Dalgona coffee trials, from left: sugar, salt, and just coffee and water.
At first, Kuntzleman wondered if the whipped coffee wasn’t something like churning butter. But after a handful of trials and some time to think, he revised.
“I tentatively suggest that what we're seeing with the dalgona coffee is very similar to what goes on when you make egg foams such as meringue,” he tells Popular Mechanics.
To beat a meringue, you must use only egg whites—even a speck of residual fat in a bowl, let alone a trace of egg yolk, will stop your entire batch of egg whites from foaming up.
Kuntzleman says the reason egg whites fluff up so easily into such a stable foam is in their proteins. “These proteins are folded into a particular shape in which the hydrophilic portion of the protein is on the outside, in contact with the surrounding water, while the hydrophobic portion of the protein is on the inside, unable to interact with the ‘outside world,’” he explains.
He continues:
“The beating process unfolds the protein strands into linear chains. The beating process allows air bubbles, pushed into the mixture through the beating process, to interact with the hydrophobic portion of the protein. [T]he air preferentially interacts with the hydrophobic portions over the hydrophilic portions. The protein chains become scrambled together, and air gets trapped inside, making a foam.”
Beating egg whites allows air to sneak into the heart of each protein strand, where the air becomes trapped and begins to bulk up in the form of foam. If there’s fat in play, that disrupts how your protein strands are able to trap and hold air. Because of this, skim milk, which has the least amount of fat on the market, foams the best for use in coffee drinks. Soy and other non-dairy “milks” with fat can still foam, but they’re often aided by stabilizers like soy lecithin or carrageenan.
Virtually all coffee shop milk products have sugar. Milk naturally has sugar in the form of lactose, and the naturally occurring sugars in soy or coconut milk is boosted with added sugar for taste. Smithsonian describes sugar’s role succinctly: It “works like a glue that holds the foam together.”
Salt doesn’t work as any kind of glue, but research shows salt does inhibit rather than fully prevent bubbles from coalescing, which explains why it performed okay in the whipped coffee mix.
When you mix dry instant coffee, sugar, and water and then agitate it, you’re making a kind of ersatz coffee meringue. Instant coffee is made by “treating ground-roast coffee with hot water and high pressure to extract the water-soluble compounds,” Adriana Farah wrote in 2012. The mixture is freeze dried, and although the crystals dissolve cleanly into water according to the naked eye, they’re still composed of the protein, fiber, minerals, a micro amount of fat—what you’d find in brewed coffee.
The repeated viral whipped coffee recipe is to use two tablespoons each of coffee, sugar, and water. For most instant coffees, a prescribed “cup” of coffee is one teaspoon of crystals mixed into six ounces of water. By using six times more crystals in one twelfth the water, then adding two tablespoons of sugar “glue,” we’re really doping the chemical reaction in favor of building foam.
Our coffee proteins are very concentrated and aided by the sugar. As they agitate, they twist and change and fill with air. This is why the reaction can work without sugar, but sugar helps to make a much richer, more stable foam out of the coffee proteins.
Both Kuntzleman and I wondered if instant coffee itself has an advantage in making whipped coffee. “It could also be that the instant coffee contains stabilizers that the ground coffee does not,” he says.
My instant coffee lists just coffee and caramelized sugar. Last year, Mel examined a jar of Folgers crystals, which simply says “coffee.” Neither Kuntzleman nor I could find information about any trace amounts of stabilizers instant coffee might have, but I wonder if the high relative proportion of dietary fiber in brewed coffee innately adds structural stability. I don’t know—it works for fiberglass!
You can also use decaffeinated coffee crystals to make whipped coffee, as long as they’re made from coffee beans instead of a clever substitute like chicory. Could a sweetener like molasses or corn syrup work as well as dry sugar? What if you try salt, like Kuntzleman did?
If you have the ingredients on hand, making whipped coffee is a little piece of science that seems like magic. Give your own a shot and tag @PopularMechanics on Instagram to show us how it turned out.
From:
Caroline Delbert
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.
