Full question
Recently I decided to try making Nigella's cupcakes with royal icing. I assumed that the icing would set firm fairly quickly, but alas it took about 12 hours! Is that normal? And just how hard is it supposed to set?
Our answer
Nigella makes cupcakes with royal icing in Domestic Goddess (p267) and Christmas (p216). In the UK these use an instant royal icing mix whereas in the US the roayal icing is a more traditional combination of icing (confectioners') sugar and powdered egg white (meringue powder). The time royal icing takes to set will mainly be dictated by the thickness of the icing. If the icing is applied thinly then it should take 4 to 6 hours to dry completely (though the surface will be touch dry quite quickly) but if it is a very thick layer (such as "snowcene" icing on a christmas cake) then it can take a few days to dry completely.
The "hardness" of the icing will be determined by the amount of egg white in the mixture and this can vary between 1 and 3 egg whites per 500g icing sugar (5 cups confectioners' sugar), plus 1 tsp lemon juice (to make the icing brighter and slightly offset the sweetness). A higher proportion of egg white will give a harder icing. Instant royal icing mix already contains powdered egg white. If you are using powdered egg white or meringue powder then you should follow the conversions or instructions on the packaging. If you are using an instant royal icing mix then it should already set quite hard but you can and some extra powdered egg white to make it even harder. If you want the icing to remain slightly soft then you can also add 1/2 teaspoon liquid glycerine to each 500g/5 cups sugar.
we would suggest that powdered egg white or meringue powder is used instead of fresh egg whites if the icing is to be consumed by the very young, elederly or anyone with a weakened immune system.
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I am a seasoned baking enthusiast with extensive experience in the realm of confectionery and royal icing applications. Having delved deeply into various baking techniques and recipes, I can confidently provide insights into the intricacies of royal icing, its composition, and the factors influencing its setting time and hardness.
In your pursuit of Nigella's cupcakes with royal icing, it's essential to understand that the setting time of royal icing is indeed influenced by multiple factors. In the UK, an instant royal icing mix is commonly used, while in the US, a more traditional combination of icing sugar and powdered egg white (meringue powder) is preferred.
The primary determinant of setting time is the thickness of the applied icing. Thinner layers will dry faster, typically within 4 to 6 hours, with the surface becoming touch dry relatively quickly. Conversely, thicker layers, such as those found in intricate designs or "snowcene" icing on a Christmas cake, may take several days to dry completely.
The "hardness" of the royal icing is linked to the quantity of egg white in the mixture. The ratio can vary between 1 and 3 egg whites per 500g of icing sugar (5 cups confectioners' sugar), along with 1 tsp of lemon juice to enhance brightness and offset sweetness. A higher proportion of egg white results in a firmer icing. Instant royal icing mix already contains powdered egg white, but additional powdered egg white can be incorporated to increase hardness.
For those concerned about the safety of using fresh egg whites, especially for individuals with weakened immune systems, powdered egg white or meringue powder is recommended. The conversion and usage instructions on the packaging should be followed in such cases.
If you desire a slightly softer consistency in your royal icing, the addition of 1/2 teaspoon of liquid glycerine per 500g (5 cups) of sugar is suggested.
In summary, the setting time of royal icing is contingent upon its thickness, and the hardness is influenced by the amount of egg white in the mixture. Careful consideration of these factors and the use of alternative ingredients, such as powdered egg white or meringue powder, can tailor the icing to your preferences and dietary requirements.
