Name: Lemon Pie Filling
Ingredients: Juice and zest of 2 lemons; 2 cups sugar; 1 whole egg; 2 egg yolks; 1 tablespoon flour; 1 tablespoon cornstarch; 1½ cups cold water; 2 egg whites (for topping)

Why it works: Sugar and flour are a kitchen classic. They rank in the top 15% of all ingredient pairs, and cooks put them together in 92,116 recipes. Both carry phenylacetaldehyde, which smells hawthorne, honey. The science ↓

Lemon Pie Filling

Ingredients

Directions

Make the filling

Combine the lemon juice, sugar, whole egg, egg yolks, flour, cornstarch, and cold water in a saucepan.
Cook over medium heat, stirring constantly, until the mixture thickens.

Prepare the topping

Beat the egg whites until stiff peaks form and set aside for topping.

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.

Sugar + flourtop 15% of all pairs

Smell alikemoderate

Cooked together92,116 recipes

Shared aroma: phenylacetaldehyde (hawthorne, honey).
Egg + flourtop 15% of all pairs

Smell alikelow

Cooked together106,462 recipes

Shared aroma: isobutyraldehyde (malty, green).
Lemon + flourtop 17% of all pairs

Smell alikemoderate

Cooked together30,404 recipes

Shared aroma: isobutyraldehyde (malty, green).
Lemon + sugartop 18% of all pairs

Smell alikelow

Cooked together53,532 recipes

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

Smell alikelow

Cooked together44,316 recipes

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

Egg and flour barely smell alike, yet cooks put them together in 106,462 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 yolks: Add richness and help thicken the filling as they set with heat.
Cornstarch: Thickens the filling as it heats, giving it a smooth, sliceable body.
Flour: Adds additional thickening to help the filling set with the starch.
Sugar: Sweetens the filling and balances the sharpness of the lemon juice.
Egg whites: Whipped to stiff peaks to form a light, airy topping.

The step that matters

Cooking the filling while stirring constantly. Starch needs to reach a boil to fully thicken, and constant stirring prevents the eggs and starch from scorching or lumping on the bottom of the pan. Stopping too early leaves the filling thin.

Swap the lemon

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

Raisinfits better
Vanillafits better
Lemonthe original
Figfits about as well

Fit is the average pairing score against sugar, egg, flour. 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.

Lemon Cake228 recipes

Lemon Ice147 recipes

Lemon Sherbet103 recipes

Lemon Custard64 recipes

Like knowing why a recipe works?

The free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.

Prefer an account? Create a free account to save pairings and unlock the full chemistry.

Lemon Pie Filling