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Dessert

Royal Icing

Royal icing is a smooth, spreadable glaze made from egg white, lemon juice, powdered sugar, and water.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 4 ingredients
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Why it works: Lemon and sugar are a kitchen classic. They rank in the top 18% of all ingredient pairs, and cooks put them together in 53,532 recipes. Both carry 2-nonenal, which smells fatty, green. The science ↓

Royal Icing

Ingredients

Directions

Make the icing

  1. Place the egg white in a bowl and add lemon juice or flavoring and a few drops of water.

  2. Stir in powdered sugar until the mixture is spreadable.

  3. If it becomes too stiff, add a few drops of water and stir again.

  4. Color and flavor as desired.

Ice the cake

  1. While the cake is still warm, pile the icing in the center and smooth it over the top and sides with a wet knife.

  2. If the icing hardens, cover it with a wet cloth.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

The flavor team

The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.

  1. Lemon + sugartop 18% of all pairs
    Smell alikelow
    Cooked together53,532 recipes

    Shared aroma: 2-nonenal (fatty, green).

  2. Egg + lemontop 19% of all pairs
    Smell alikelow
    Cooked together44,316 recipes

    Shared aroma: (e,e)-2,4-decadienal (fatty, deep fried).

  3. Egg + sugartop 21% of all pairs
    Smell alikemoderate
    Cooked together122,807 recipes

    Shared aroma: 2-nonenal (fatty, green).

Lemon and sugar barely smell alike, yet cooks put them together in 53,532 recipes: they work on texture and structure more than aroma.

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Egg white
Forms the base of the icing and gives it a smooth, spreadable body.
Powdered sugar
Provides sweetness and thickens the mixture into a spreadable icing.
Lemon juice
Adds acidity and bright flavor to balance the sweetness.

The step that matters

Adding water a few drops at a time. Too much water thins the icing and makes it runny, while too little leaves it stiff and hard to spread. Adding liquid gradually lets you reach a spreadable consistency.

Swap the lemon

How well each one fits the dish's main ingredients (egg, sugar):

  1. Vanillafits better
  2. Raisinfits about as well
  3. Lemonthe original
  4. Datesfits less well

Fit is the average pairing score against egg, sugar. Candidates are from the same food group and used in at least 100 recipes.

“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.

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