Trends, and especially those on social media, can pass me by without me having noticed them at all. I have one of our readers to thank for discovering one of the big drink trends on Tiktok and Instagram in spring 2020: Dalgona coffee. It’s a creamy, airy, whipped coffee drink made with just water, instant coffee and sugar.
Dalgona coffee does look beautiful. But, our reader wanted to know, why does it work? And why does it only work when you use instant coffee? My curiosity was roused, so we’re digging into the science behind Dalgona coffee!
What is Dalgona coffee?
Even though Dalgona coffee is a very recent trend online, it is not a new drink. It is a South Korean interpretation of a whipped coffee drink that has been around for a while (there are plenty of posts with recipe from before 2020). You’ll find recipes for whipped instant coffee, beaten coffee or Indian coffee that are the same thing.
So why is this Dalgona coffee? Dalgona is a Korean candy. It is made by caramelizing sugar and mixing in some baking soda. It is quite similar to honeycomb, however, contains less baking soda, so it’s slightly less puffy. The colour of Dalgona candy is a light brown cream colour, exactly the colour of Dalgona colour, hence the name association.
Quick overview of making Dalgona coffee
Making a Dalgona coffee is surprisingly easy, especially if you have access to an electric mixer. All you do is mix together instant coffee, sugar and water and whisk it. By hand, or with an electric mixer, by hand it may take some 20 minutes, whereas with an electric stand mixer it’s less than 2 minutes of mixing! Scoop the foam on top of a glass of milk and you’re done.
Really the part that’s interesting from a scientific point of view is making that foam.
Making a stable foam
Lots of scientists and cooks love making and studying foams. If you’ve ever made a meringue, eaten whipped cream or even baked bread you’ve encountered foams. Foams contain a lot of gas (e.g. air) trapped within a liquid or a solid.
In the case of meringue, whipped cream and also Dalgona coffee you use a lot of mechanical energy to mix that air within the liquid. By mixing vigorously the air gets caught in the liquid. However, just mixing isn’t enough, the liquid needs to be able to ensure that the bubbles don’t come together too fast. In other words, they need to stabilize the bubbles just long enough so they can be made smaller and smaller while whisking.
Have you ever tried whisking water into a foam? No matter how hard you mix, it won’t foam and any air bubbles that you might have formed will disappear almost immediately.
Foaming instant coffee
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However, 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 gram of instant coffee) and you’ll get a very light and airy foam (see photo below).
Unfortunately, the foam isn’t very stable, in a matter of minutes it has shrunk considerably and an hour later the foam has lost most of its smaller bubbles, some larger structures are left.
So, why can foam instant coffee so much better than pure water? Luckily, scientists have been studying the foam on coffee, especially espresso for years. A lot of the mechanisms at play for an espresso aren’t relevant for instant coffee though since those are influenced by the beans as well as the processing methods. However, the ingredients of an espresso are very similar to that of instant coffee.
Foams can be stabilized well by surfactants. Surfactants is an abbreviation for surface active agents. These ingredients help stabilize a foam by sitting on the interface of the gas and liquid. This way they make it easier to form small stable bubbles. By adding surfactants to water it becomes a lot easier to stabilize and thus form the small air bubbles. It’s why egg white, which is just water with surfactants such as proteins, foams so well!
Coffee contains a small amount of proteins, fats as well as larger polysaccharides. It has been shown that all these ingredients contribute to foam formation and stability in the role of surfactant. Even caffeine might play a minor role, especially in the presence of sugar.
Sugar stabilizes the foam
Making a foam from just instant coffee and water works, however, it doesn’t look as luscious as the ‘original’ version with sugar. Sugar plays a crucial role in making the super fluffy foam.
Even though the surfactants in coffee serve well to help stabilize bubbles while you’re foaming the liquid, they aren’t strong enough to maintain the foam. Instead, gravity will pull the liquid down, air bubbles float up and air bubbles merge together. This is where sugar comes in.
Sugar dissolves in the water mixture. This increases the viscosity of the liquid, it becomes more syrupy. This makes it harder for bubbles to merge together again, but also makes it harder for the liquid to move down and for the bubbles to move up through the more viscous matrix. As a result, the foam is a lot more stable. The role is very similar to that of sugar in an egg white meringue.
Sugar also increases the volume of the foam though. It does so first of all by simply increasing the overall mass of the mixture. In the recipe at the bottom of the post it makes up more than a third of the overall mass. But also the increase in viscosity here likely helps. Interestingly, adding sugar to egg whites doesn’t necessarily impact volume, but ratios of water:dry ingredients are quite different there.
Why Dalgona coffee has to be made with instant coffee
A lot of articles online discuss alternative ways to make Dalgona coffee, the more extensive ones all stretch the fact that you can’t make it with regular coffee, you need instant coffee.
What is instant coffee?
To understand why this is the case, let’s first have a look at what instant coffee actually is! Instant coffee is dried coffee. To make instant coffee manufacturers take coffee beans, grind them and extract their flavour. In other words, they make coffee, but on a very large scale.
Once that coffee is made they then dry the coffee again 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. They use various techniques such as agglomeration to ensure that dried coffee dissolves very rapidly when it comes into contact with water. As such, instant coffee dissolves very rapidly in water, whether that water is warm or cool/room temperature.
Instant coffee is a good way for manufacturers to use up beans that can’t be stored for longer. For consumers it comes with the benefit of only needing to stir water and powder together!
The benefit: concentrating those surfactants
Ratios vary (they’re generally given on the package) but to make instant coffee you will add about 1 tsp of instant coffee (which is only about 1 gram) to 250ml of water. This large amount of water dilutes all the surfactants present in coffee that are so important for making a foam.
The benefit of instant coffee though when making Dalgona that it is very easy to concentrate all the important components. Just add less water. It is why recipes for Dalgona tend to use only 30 ml of water with a heaping amount of 6g of coffee making these foams way stronger than a regular cup of 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 really concentrate it well 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 it’s made from just coffee beans and water. However, there are a lot of ‘fancy’ instant coffees out there on the market as well. These may contain other ingredients aside from the coffee. Some of these ingredients won’t give any challenges to you Dalgona coffee. However, some may. Salt for instance is known for interacting with foams negatively.
Also, keep in mind that Dalgona coffee hides a lot of those coffee flavours with all the sugar. As such, you might not want to waste your flavoured coffee to a Dalgona coffee. But who knows, give it a try, it might just be the next big thing!
Making Dalgona with ground beans
You can’t just mix water and ground coffee together and whip them together. You have to extract all the flavours and other actives components to make a good tasting and foaming smooth coffee foam.
If you use regular drip or espresso coffee, it will turn out too dilute to foam up. 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, highest quality beans. As such, instant coffees do have a bit of a reputation for being less nuanced in flavour. If you are looking for a strong, less bitter coffee flavour, your best shot is to change your instant coffee. Buy another brand or buy one from an artisan maker. Some make their own instant coffees with pretty special flavours! Remember that the bean quality and roasting process have a huge impact on flavour, so using one that you enjoy will make your Dalgona considerably better.
It’s sweet, very sweet
Even though a Dalgona coffee doesn’t taste very bitter, it does contain a lot of coffee! You have all the sugar to thank for that. Sugar hides a lot of the more bitter coffee flavours. The same mechanism is at work in most soft drinks which are actually very acidic. Their acidity is hidden by the sugar in the drink.
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.
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.
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.
Not want to use any sugar?
If you don’t want to use any sugar, there’s another option (but beware, this will be quite bitter!): use xanthan gum. 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. Remember that a Dalgona foam consists of more than 33% of sugar.
The two drinks below are made with the same amount of coffee and water. The one on the left also contains sugar, whereas the one on the right doesn’t contain any, just xanthan gum.
- 2 tbsp (= 6g) instant coffee
- 2 tbsp (= 30g) water (see post for temperature, best to be cool or room temperature)
- 2 tbsp (= 20g) sugar
- 0.5l (roughly 1 pint) of milk*
- Mix the instant coffee, water and sugar in a bowl. This quantity is large enough to whip up in a regular stand mixer, or you could use a separate electric mixer.
- Whip for long enough until the mix turns a light brown and has visibly increased in size. You're not at much at risk of over whipping as you are with egg whites or whipped cream. However, at some point, more mixing won't help any further and might only start breaking up bubbles.
- Fill two glasses with milk (warm or cold, however you prefer to drink it) and scoop the foam on top. Drink it as such or mix the foam through a little.
*In all honesty, it doesn't matter at all which liquid you use here. The milk does not have a structural role. Use something that works well with a strong sweet coffee flavour. Milk is the most common one since it's traditionally used with drinks like a cappuccino. If you wanted though, you could use orange juice (not sure I'd recommend that flavour wise!) or any type of non-dairy milk for instance.
- 2 tbsp (= 6g) instant coffee
- 2 tsbp (= 30g) water
- 1/8 tsp xanthan gum
- Mix all the ingredients together in the bowl of a stand mixer (you can also whip by hand or with an electric mixer, whisking by hand does take a considerable amount of time).
- Whisk the ingredients together. Start on a slow setting to prevent splashing and turn up to a maximum speed once it starts to thicken and doesn't splash as much anymore.
- Enjoy on top of a glass of warm or cold milk. Keep in mind that this version has a very strong coffee flavour!
Comparing foams over time
Still reading?! You might be interested to see just how the stability of all those different foams differs. The photo below shows the regular Dalgona coffee on the left, the sugar free with xantham gum in the middle and the pure whipped instant coffee on the right. This photo was taken about 2 hours after making all the foams.
Air and colour
You can see that all have changed colour, they’re darker in colour. This is a sign that they’re losing colour. As you notice while whipping the foam, they turn lighter in colour when whisked more. This is because of how the air bubbles reflect light differently. Once they start losing these bubbles again the colour turns darker again.
Also have a look at the black layers of liquid at the bottom of some. This is liquid from the foam that has sunk down the glass again. If you wait long enough all of them will at some point return back to a liquid.
Storing the foams
You can delay foam drainage and loss of bubbles by storing the foams in the fridge. The colder temperatures makes the liquid more viscous, and, as we discussed earlier, that will help stabilize the foam. If they do sink in you can whip them back up, just like an Italian meringue!
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!
Chefsteps, This is not a latte!, Sep-15, 2016, YouTube, link
Jenni Field, How to make beaten coffee, link
James Hoffman, Dalgona coffee – explained & upgraded, Mar-31, 2020, link
Ernesto Illy, Luciano Navarini, Neglected food bubbles: the espresso coffee foam, 2011, Food Biophysics, 6:335-348, link
Jin Joo, Dalgona – Korean sponge candy, Aug-28, 2019, link
Jin Joo, How to make Dalgona coffee, Mar-24, 2020, link
Mikova, K., Bovskova, H., Optimization of egg white foaming, link
OpenKitchen, Korean Sugar Candy, Dec-10, 2019, YouTube, link
Fernando M. Nunes, Manual A Coimbra, Influence of polysaccharide composition in foam stability ofespresso coffee, Carbohydrate Polymers 37 (1998) 283-285
Arundhuti Rama, Powerful and creamy Indian Espresso Coffee, June, 2, 2011, link
Whisk affair, How to make beaten coffee (Indian style cappuccino coffee), Oct-13, 2017, link