Learn the science behind:
Trends, and especially those on social media, are short-lived. They’ve often passed well before I even noticed them. I have one of our readers to thank for discovering the Dalgona coffee trend in spring 2020. This creamy, airy coffee drink is made with just water, instant coffee, and sugar.
Our reader wanted to know, why does it work? How does it get so foamy? And, why does it only work with instant coffee?
My curiosity was aroused. I made a range of Dalgona coffee drinks, probably long after the trend had reached its peak. And have some explanations for you as to how and why dalgona coffee can be so light and foamy. Who knows, maybe it becomes trendy again at some point?
- What is Dalgona coffee?
- Making a stable foam
- Why Dalgona coffee has to be made with instant coffee
- Can you make Dalgona without instant coffee?
- The flavour of Dalgona coffee
- Troubleshooting Dalgona coffees
What is Dalgona coffee?
Even though Dalgona coffee was a sudden trend, it wasn’t a new drink. It seems to be a South Korean interpretation of a whipped coffee drink that has been around for a while. There are plenty of pe-2020 recipes for whipped instant coffee, beaten coffee, or Indian coffee, which are all the same thing.
So where does the name Dalgona come from? Dalgona is a Korean candy, made by caramelizing sugar and mixing in baking soda. It is quite similar to honeycomb, but is flatter, because of a lower amount of baking soda. Dalgona candy has a light brown cream color. Dalgona coffee has too. Hence the association.
How to make Dalgona coffee
Making a Dalgona coffee is surprisingly easy, especially if you have access to an electric mixer.
Mix together instant coffee, sugar, and water in the right ratios. Whisk it, by hand, or with an electric mixer. After enough time, about 2 minutes with an electric mixer, up to 20 minutes if doing by hand, you’ll get a light and airy coffee. The foam is sweet and has a strong coffee flavor.
Most people scoop the foam on top of a glass of milk. Ready to be enjoyed.
Making a good Dalgona coffee is all about the foam. So let’s have a closer look at how that works. And, let’s have a look at why we need to use instant coffee.
Making a stable foam
Dalgona coffee is a great example of a light and airy foam in food. Foams’ light and airy texture make for quite a special eating experience. But, they’re also notoriously unstable and challenging to make. Dalgona coffee collapses over time, just like whipped cream or an unbaked meringue would. To make a sufficiently stable foam you have to achieve three things:
- You need to incorporate air into your mix; intense whisking can do that
- Something then needs to hold on to that air. If you’ve ever tried to whisk pure water. You’ll know what that means, no matter how hard you whisk air bubbles will disappear almost immediately from water.
- Even after you’ve managed to create all those tiny air bubbles in your foam, you then need to ensure they don’t dissipate too quickly.
Meringues, whipped cream, as well as a loaf of bread are all other examples of foam. Foams are made up of gas (e.g. air) trapped within a liquid or a solid. Read all about the science of foams here.
Foaming instant coffee
Whereas you can’t make a foam out of pure water, you can make a foam of an instant coffee + water mixture.
Just whisk water and instant coffee in a weight ratio of 5:1 (e.g. 30g of water with 5 grams of instant coffee) and you’ll get a very light and airy foam (see photo below).
Unfortunately, as you can see, the foam isn’t very stable. You’ve successfully completed step 2: making a foam. But, you’re failing step 3: maintaining the form. In a matter of minutes the foam has shrunk considerably. Half an hour later the foam you can see that a lot of the liquid has sunk back down to the bottom. Only a meager bit of foam is left on top.
Why can you make a foam out of instant coffee?
So, why can you foam instant coffee so much better than pure water?
Luckily, scientists have been studying coffee foams, especially those on espresso, for years. One of the (many) mechanisms that help to create a foam out of (instant) coffee is the coffee itself.
Coffee contains a small amount of proteins, fats, and some larger polysaccharides. It has been shown that all these molecules can contribute to creating a more stable foam. Even caffeine might play a minor role. They do so by serving as surfactants.
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Surfactants can help form foams
Foams can be stabilized by surfactants, which are surface-active agents.
Remember that a foam such as the one in Dalgona coffee, consists of a lot of small air bubbles dispersed within a liquid. These air bubbles will want to find each other and merge together. As a result, the air bubbles grow and it becomes easier for them to escape. You could see that on the photo above of whipped instant coffee.
Surfactants can stabilize a foam by sitting on the interface between the gas and liquid. They make it less attractive and easy to air bubbles to find each other and merge. As a result, it is easier to form small stable bubbles.
The surfactants in coffee are strong enough to help create a foam. However, they’re not strong enough to stabilize the foam over time. Once you stop whisking, the foam will slowly collapse.
Surfactants aren’t unique to coffee, they occur in a lot of other foods. A common example would be egg whites, which can be used to make very stable foams: meringue.
Sugar stabilizes the foam
This is where the role of sugar in Dalgona coffee comes in.
Yes, you can make a foam from just instant coffee and water. However, it doesn’t look that luscious, nor is it very stable. If you want that thicker, smooth, more stable Dalgona coffee, you need sugar.
By increasing the viscosity
Sugar dissolves in water. In doing so, it increases the viscosity of the liquid, it becomes more syrupy, thicker. This makes it harder for bubbles to merge. And, it also makes it harder for the liquid to move down and for the bubbles to move up. As a result, the foam is a lot more stable. The role is very similar to that of sugar in an egg white meringue.
Enabling a way fluffier and bigger foam!
Sugar also increases the volume of the foam of a Dalgona coffee. Of course, since you’re adding more ingredients, you have a bigger overall mass. But, it’s not just that.
In a typical Dalgona coffee, only 1/3 of the overall mass may consist of sugar. Nevertheless, if you look at the photo below, adding sugar can easily double, if not triple the volume of a Dalgona foam!
Why Dalgona coffee has to be made with instant coffee
Almost all Dalgona coffee recipes stretch the fact that is has to be made with instant coffee. Regular coffee won’t do. But why? It’s all about concentrations.
What is instant coffee?
Keep in mind that instant coffee is dried coffee.
To make instant coffee manufacturers start by roasting, and grinding coffee beans. Next, they extract the coffee flavor from those beans. Aka, they make liquid coffee, like you would at home, but on a very large scale.
Next, they dry the coffee using special drying processes. Since the majority of coffee, well over 90% is made of water, you will only be left with a small amount of powder. Along the way, they process the powder in such a way – using a technique called agglomeration – to ensure it dissolves rapidly, even in cold water.
The benefit: concentrating those surfactants
So, instant coffee is dried coffee. And the advantage of using dried coffee is that you can determine the concentration of that coffee. You can add a little water, or a lot. You don’t have this wide degree of flexibility when making ‘regular’ coffee.
To make a ‘normal’ cup of coffee using instant coffee you may need about 1 tsp of instant coffee (which is only about 1 gram) 250ml of water.
For making Dalgona though, you may use a whopping 6g of instant coffee in just 30 ml of water. That’s at least 5 times the amount of coffee, in just 1/8th the amount of water.
By using such a high concentration of coffee, you also have a high concentration of surfactants. It’s why you can foam this super-concentrated instant coffee, but why you can’t foam your regular coffee. There aren’t enough surfactants to stabilize all those necessary air bubbles.
Can you make Dalgona without instant coffee?
Making Dalgona with strong espresso
You might be wondering whether you can just make a Dalgona with a very strong espresso. One with only a small amount of moisture, but a large amount of powder. Unfortunately, by the nature of the coffee-making process, you can’t concentrate it enough. Water has to pour through the ground coffee and it just can’t take along as many of these active components.
That doesn’t mean you can’t make a foamy espresso! On the contrary, you can, with an electric mixer, see photo below. Adding sugar will make it even lighter. Notice how adding the sugar makes the air bubbles much smaller in size? The final foam won’t be as luscious and creamy as the instant coffee one. Also, it does collapse a lot faster.
Making Dalgona with flavoured instant coffees
Regular instant coffee is made from brewed coffee and nothing else. The type of bean may vary, as may the roasting levels, but that’s it.
What about the ‘fancy’ instant coffees? Ones with added flavors for instance? Some of these will work fine for a Dalgona. A little bit of flavor, won’t interfere with your foam-making ability. But take care, salt for instance is known to negatively impact foaming. And extra (milk) proteins may also influence your foam, some for the better, some for the worse.
Making Dalgona with ground beans
You can’t just mix water and ground coffee together and whip them together. You’ll be left with a lot of solid coffee particles, that prevent foaming and give an undesirable texture to your foam.
Also, regular drip coffee will be too diluted to foam. If you do want to use ground coffee you have two options.
First, you could try to use Turkish coffee. You make Turkish coffee by heating very finely ground coffee with water in a small coffee vessel. Various heating cycles ensure that you extract all flavours. By adding some more coffee you can concentrate the coffee. Do take care, Turkish coffee contains a lot of coffee solids and you don’t want these to end up in your coffee.
Alternatively, you could use regular ground coffee. Place the coffee in a filter and pour in the hot water. Let the coffee sit in the hot water for several minutes to extract a good amount of the coffee. Squeeze out all the moisture and test.
Both these methods are more finicky and you’ll likely need a few attempts to get the concentrations just right for your type of coffee and system!
The flavour of Dalgona coffee
As hinted by its name giver, Dalgona candy. If you like sweet, milky, with a hint of caramel and not too strong a coffee flavour: then a Dalgona coffee is great for you! If you’re looking for a strong good coffee flavour though, Dalgona coffee is probably not the choice for you (although it’s fun to make!).
Instant coffee generally isn’t made from the best quality beans. As such, instant coffees do have a bit of a reputation for being less nuanced in flavor. If you are looking for a less bitter coffee flavor of the Dalgona, try a different instant coffee. Buy another brand or buy one from an artisan maker. Some artisan coffee makers make instant coffees with special flavors! Remember that the bean quality and roasting process have a huge impact on flavor, so using one that you enjoy will make your Dalgona considerably better.
This applies even more so when making cold-brew coffee. The quality and flavor of the bean will determine the quality of your coffee.
It’s sweet, very sweet
Even though Dalgona coffee doesn’t taste very bitter, it does contain a lot of coffee! You have the sugar to thank for that. Sugar hides a lot of the bitter coffee flavors. Keep this in mind when drinking it. You may drink a lot more coffee than you realize.
Troubleshooting Dalgona coffees
Even though the recipe for a Dalgona coffee is pretty simple, there are still some things that can go wrong, or can be optimized.
What temperature should the water be?
You can make Dalgona coffee with regular, room temperature water. There is no need to use hot boiling water. In fact, using cooler water tends to help form that foam. At a lower temperature, the viscosity of your liquid mix will be higher, it is thicker. This helps to hold onto those air bubbles. If your mix doesn’t whip up well, try cooling it down a bit (don’t freeze it, ice doesn’t whip up well!).
It is important to keep in mind that the water needs to be warm enough to dissolve all the sugar you’re adding. Sugar dissolves water and better in warm water. If you notice that not all the sugar dissolves at the start, give the mix a quick heat in the microwave or on the stovetop to dissolve it. Alternatively, stir it and just wait a few minutes, more of the sugar will dissolve with some patience.
How can you reduce the sweetness of Dalgona
If you think your Dalgona is too sweet, you can definitely reduce the sugar content. However, keep in mind that it will become less foamy. Also, it will be less stable. If you’re planning to drink your Dalgona within half hour after making that shouldn’t be a problem though.
If you don’t want to use any sugar, there’s another option: use xanthan gum. Be aware though, this one will be quite bitter since you no longer have the sweetness of the sugar covering that up.
Remember that, aside from providing sweetness, the main role of sugar is really to thicken the liquid to allow more air to be whipped in. You can achieve that same effect by adding a thickener and xanthan gum is very good at that (it’s why it’s used in ice cream as well).
Xantham gum stabilizes the coffee foam in a similar way as sugar does. However, since you only need a very small amount, a lot less than sugar, you will end up with less foam.
How long can you store Dalgone for?
Made a successful Dalgona, but can’t finish it all in one go? Unfortunately, Dalgona coffee isn’t very stable. It will collapse quite rapidly. To stretch your Dalgona, try to:
- Store it in the fridge
- Just whisk your Dalgona again! Chances are you’ll be able to foam it up again.
Robert J. Bergeron, et al., Method for reducing foam in instant coffee, United States Patent Office 3,436,227, Patented April 1, 1969, link ; this patent actually tries to prevent any foam formation!
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