Name: Apple and Lemon Filling
Ingredients: 1 apple, grated; 1 lemon, juice and grated rind; 1 cup sugar

Why it works: Apple and lemon are a kitchen classic. They rank in the top 14% of all ingredient pairs, and cooks put them together in 7,551 recipes. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓

Apple and Lemon Filling

Ingredients

1 apple, grated
1 lemon, juice and grated rind
1 cup sugar

Directions

Grate the apple and the lemon rind.
Place the grated apple, lemon juice, and sugar in a saucepan over medium heat.
Boil for 5 minutes.

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.

Apple + lemontop 14% of all pairs

Smell alikemoderate

Cooked together7,551 recipes

Shared aroma: trans-2-nonenal (cardboard, fatty).
Apple + sugartop 18% of all pairs

Smell alikelow

Cooked together16,478 recipes

Shared aroma: beta-damascenone (apple, rose).
Lemon + sugartop 18% of all pairs

Smell alikelow

Cooked together53,532 recipes

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

Apple and sugar barely smell alike, yet cooks put them together in 16,478 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

Apple: Provides bulk, body and natural pectin that helps the filling thicken as it cooks.
Lemon: Adds acidity that brightens the flavour and balances the sweetness of the sugar.
Sugar: Sweetens the filling and, as it dissolves, helps give it a glossy, syrupy texture.