Name: Orange Filling for Cake
Ingredients: 2 egg whites; 1 pound powdered sugar; grated rind and juice of ½ lemon; 2 oranges, grated; sugar (to taste, for thickening)

Why it works: Lemon and orange match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 10,634 recipes. Both carry 3-hexenal, which smells apple, fruity. The science ↓

Orange Filling for Cake

Ingredients

Directions

Stir the egg whites and powdered sugar together until well combined.
Add the grated rind and juice of the lemon and the grated oranges.
Mix thoroughly and spread between cake layers.

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.

Lemon + orangetop 1% of all pairs

Smell alikestrong

Cooked together10,634 recipes

Shared aroma: 3-hexenal (apple, fruity).
Sugar + lemontop 18% of all pairs

Smell alikelow

Cooked together53,532 recipes

Shared aroma: 2-nonenal (fatty, green).
Egg + lemontop 19% of all pairs

Smell alikelow

Cooked together44,316 recipes

Shared aroma: (e,e)-2,4-decadienal (fatty, deep fried).
Sugar + orangetop 20% of all pairs

Smell alikelow

Cooked together19,212 recipes

Shared aroma: beta-damascenone (apple, rose).
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: Provide structure and body, helping the filling set thick and hold together.
Powdered sugar: Adds sweetness and body, dissolving smoothly into the filling for a fine texture.
Oranges: Contribute bright citrus aroma and flavor, plus liquid from the grated fruit.
Lemon: Adds acidity and freshness that balances the sweetness of the filling.