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Dessert

Royal Icing

Royal icing is a sweet, glossy glaze made from egg whites, icing sugar, and lemon juice.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 3 ingredients
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Why it works: Sugar and lemon 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

Oven, in the book's wordsA slow oven

Ingredients

Directions

Make the icing

  1. Place the egg whites in a bowl.

  2. Sift the icing sugar through a sieve.

  3. Add the icing sugar to the egg whites and mix well.

  4. Stir in the lemon juice until smooth.

Finish the cake

  1. Spread the icing evenly over the cake, dipping the knife in cold water as needed.

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. Sugar + lemontop 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).

Sugar and lemon 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 whites
Whisked into a foam-free base that gives the icing body and a glossy set.
Icing sugar
Provides sweetness and bulk, and dissolves into the egg whites to thicken the icing.
Lemon juice
Adds acidity that brightens the sweetness and helps keep the icing smooth.

The step that matters

Spread the icing evenly over the cake. Icing sets quickly as it dries. Dipping the knife in cold water keeps the surface smooth and prevents the icing from dragging and tearing, which can leave uneven patches.

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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