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Trying to decorate cookies or a cake with royal icing? But having issues getting the icing just right? If so, you’ve come to the right place!
Even though royal icing might seem to be finicky, it is actually quite a simple product. Once you understand the role of its 2 (!) ingredients and 1 (!) process step, you’ll be able to fix any royal icing that comes your way :-)!
- How does a royal icing work?
- The role of ingredients in royal icing
- Fixing royal icing challenges
- Need decoration advice?
All photos of royal icing in this article were made with a base of 100g powdered sugar + 1/8 tsp of red food coloring. No sugar and coloring were added during the experiments, the only parameters that were changed were the water & egg white powder content.
How does a royal icing work?
Royal icing is a type of icing that sets quite hard and quickly. Also, it can be tweaked to make both very intricate decoration details, as well as be used to quickly coat larger surfaces.
Making royal icing
To make royal icing, all you need to do is whisk together egg white (powder), icing sugar, and water (if not using liquid egg whites). In doing so, you’re creating a foam. Once it’s whisked and aerated, it’s ready to go. No heating, cooking, just mixing and whisking.
Royal icing is very closely related to meringues. As a matter of fact, you could say royal icing is a highly concentrated version of a meringue, with a lot of sugar.
The role of ingredients in royal icing
Since there are so few ingredients, every ingredient plays a crucial and quite specific role. Knowing what that role is will help you in troubleshooting your royal icing.
We’ll start with the main ingredient: icing sugar (or powdered or confectioner’s sugar, they are all the same thing). Icing sugar is sugar that has been milled to create a very fine sugar, with small particles. Just compare icing sugar and regular sugar, the crystals are noticeably smaller than that of ‘regular’ sugar. In royal icing, powdered sugar has quite a few roles.
We can be short about this one, sugar adds sweetness and thus flavor to the icing
Powdered sugar literally fills the royal icing. The sugar crystals pack tightly within the icing and thicken the frosting. By thickening the liquid it helps the egg whites (we’ll discuss those further down) to hold on to the air by making it harder for air bubbles to move through the liquid.
The high amount of sugar prevents (or at least delays) the growth of microorganisms. At room temperature egg whites can spoil within a few hours outside of the fridge. The high amount of sugar lowers the water activity and as such extends the shelf life by several days!
Egg white powder (the dry ingredients in egg white)
About 10% of egg whites are proteins. You can use liquid egg whites which contain these proteins. However, you can also use dried egg white powder. These are egg whites from which the water has been removed. They have the same functionality, with the added benefit that by removing the water they can be stored for months at room temperature.
Stabilizing air bubbles
The proteins play a crucial role: they stabilize the air bubbles in the icing that you whisk in. They do so by sitting on the interface between the air and water, keeping the air bubbles in their spot.
If all egg proteins are ‘busy’ holding on to air bubbles, whisking the mix any longer won’t have any impact. There simply aren’t enough proteins to hold on to the air. At this point, you can only add more air by adding additional egg white powder. (In some cases you might also need extra water, see below.)
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Egg white liquid / Water
Aside from the proteins, egg whites are mostly made up of water, roughly 90%. If you don’t use liquid egg whites, but the powdered version, you can simply add back water to reconstitute the egg whites.
Viscosity / Flowability
Water is the only liquid component in your icing. As such, it ensures the icing can flow. Just do a quick thought experiment, if you leave out the water, all you’d be left with are dry powders. These will never ‘flow’ to create an icing.
As such, water can loosen up and thin a royal icing. Even a slight amount of water can have a big impact on the consistency of your royal icing. Generally speaking, it is best to start by adding too little water, instead of too much. It is easy to add a little additional water. However, once there’s too much water, you will need a lot more sugar and egg white powder to bring it back to the right consistency.
Enabling more aeration
This second effect may sound contrary to the first. Adding more water can, to a certain extent, increase the amount of air that can be incorporated. It’s best demonstrated by a thought experiment. Imagine you have 100g of powdered sugar with 1 tsp of water. All of this water will be used to dissolve sugar. You can’t aerate (= add air) this mix, it will be dry, powdery, and clumpy. However, add a few more teaspoons of water and you will be able to aerate it. There is now enough liquid to incorporate air into
Recommendation on liquid vs dry eggs
We recommend using egg white powder + water instead of liquid egg whites. By doing so, you have full creative freedom over the ratio of egg white proteins: water. You can change the two independently this way, while if you’re using liquid egg whites you’re pretty much stuck with a fixed water:egg protein ratio. You can dilute it by adding more water, but you can’t concentrate it.
There’s no need for this ingredient to be on our ingredient list, it’s all around us, available freely! But it is very important for royal icing to become royal icing. When whisking royal icing you’re incorporating air in the form of air bubbles. These air bubbles are crucial to give the icing strength and resistance against cracking and they are also why the icing turns a lighter color when whisked.
Fixing royal icing challenges
So, once you’ve de-coupled all ingredients and you’re using egg white powder, water and icing sugar, you can do a lot more with royal icing than you might have ever expected! When making royal icing there are a few factors that you will want to control:
- Flowability for decoration detail: if you need to coat large surfaces, you want the icing to flow reasonably well to make a smooth surface. However, if you’re making highly intricate designs, you don’t want the icing to flow or you’ll loose all your details again!
- Meltability: if your icing is too hard, it might not melt wel in your mouth, you might be looking for the icing to melt in the mouth to add sweetness to whatever it is you’re decorating!
- Strength: icings can protect what it is they are decorating. Some crack very easily, others don’t the strength is determined by its ingredients.
So let’s look at a range of scenarios and how to fix them.
Meringue powder is a powder developed to easily make meringues. As such, it contains egg whites and sugars in a predetermined ratio.
It’s perfectly fine to use for making royal icing. But, it does have a major disadvantage. Since it contains both egg white and sugar, your creative freedom is a little limited. You can’t adjust the egg white content without also impacting the sugar content. That said, it also is more flexible than using liquid egg whites.
You’ve added too much water to the royal icing. The best way to fix this is to start adding a little extra powdered sugar. If you need a large amount, also add some extra egg white to keep the ratio egg whites:powdered sugar the same.
Just add a little extra water. Be careful, a little water can already make a big impact! If you’re very close to your desired consistency, only add a few drops at a time. Whisk the royal icing and reevaluate before adding more water.
If you’re still pretty far off from the consistency you’re looking for, start by adding 1/8 tsp of water per 100g powdered sugar. Again, just whisk the royal icing again and reevaluate the consistency.
Reduce the amount of egg white powder in your royal icing recipe the next time you make it. The egg whites hold onto all the sugar crystals and make it harder for them to dissolve upon eating.
If you haven’t yet used your royal icing, add extra powdered sugar and water. This way you automatically reduce the egg white protein content.
To slow down the speed of melting, add extra egg white powder. Start by adding 1/4 tsp of egg white powder per 100g powdered sugar.
Add extra egg white powder to the icing. Egg white strengthens the icing, see more here.
A crucial characteristic of royal icing is that you’re incorporating air into the icing. You’re essentially making a very sugary meringue. The air bubbles are stabilized by egg proteins which sit on the interface between air and water. The hydrophobic parts of the proteins (those parts that don’t like water) will want to sit in the air, the hydrophilic parts (the parts that do enjoy water) will sit in water.
Adding fats to royal icing will compete with the air bubbles. The hydrophobic parts of the proteins also like to sit in fat, probably even more than in air. As such, they will sit around the fat particles, leaving the air bubbles to disappear!
Most people will first make their royal icing and then color it. That way they can make several colors in one go by splitting the first batch. Once you’ve optimized your royal icing, you don’t want the color to change the consistency again!
Even a little bit of water can have quite a big impact on the consistency. As such, adding a water-based color at this point probably means that you will have to add extra sugar or egg white and whisk again.
That doesn’t mean you can’t use water-based color. However, it’s best to add them at the start and that has its disadvantages as well (see next question!).
You can color royal icing at the start, as we did for our experiment. However, the color of the icing will change while making it. This is because of the introduction of air bubbles into the icing. These air bubbles scatter light in all directions, which causes the color of icing to become lighter. If you’ve made the icing before and know exactly how much color to add, you can add it at the start. Otherwise, you’re guessing at best.
The photo below demonstrates this again. The icing on the left has not been aerated (because of a lack of egg white). The icing on the right has been aerated, it’s otherwise identical but has a completely different color.
Yes, you can! Since royal icing is a (very concentrated) form of meringue, you can bake it. Baking it will dry it out even further. It might become too hard, especially if you’re already using a very firm icing type. Also, keep in mind that baking can initiate Maillard reactions, causing your royal icing to turn brown. This is especially true for lightly colored royal icings.
On the photo below you can find a comparison of royal icing applied after baking (left) and before baking (right). Notice the difference in color of both the icing and the cookie.
Need decoration advice?
As you might have noticed, we’re not cookie/cake decorating experts. Nor do we pretend to be. We can draw a simply line, make a little drawing, but those cute pretty decorated cookies? Not something we can do. We’re food scientists, so we can tell you how the icing changes, but not how best to decorate. If you need help with that, we recommend you reach out to the decoration experts. A few suggestions:
The Bearfoot Baker: Has a wonderful cookie decoration guide, with recipes and instructions on decorating with royal icing
The Decorated Cookie: as the name says, she knows a thing or two about cookie decorating with a wonderful guide