Name: Cucumber Ketchup
Ingredients: large old cucumbers; coarse sea salt; lemon peel; mace; cloves; horseradish; shallots; white pepper; ginger

Why it works: Horseradish and shallot match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 376 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Cucumber Ketchup

Ingredients

Directions

Pare and slice the cucumbers, then mash them.
Add salt and let them stand overnight.
Drain the liquid and boil it with lemon peel, mace, cloves, horseradish, shallots, white pepper, and ginger.
Strain the mixture and let it cool.
Bottle the ketchup with mace, cloves, and peppercorns, but not the other ingredients.

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.

Horseradish + shallottop 1% of all pairs

Smell alikestrong

Cooked together376 recipes

Shared aroma: coumarin (sweet, hay).
Clove + gingertop 1% of all pairs

Smell alikestrong

Cooked together6,038 recipes

Shared aroma: estragole (anise, licorice).
Cucumber + horseradishtop 2% of all pairs

Smell alikestrong

Cooked together640 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Cucumber + shallottop 3% of all pairs

Smell alikestrong

Cooked together264 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Lemon + gingertop 5% of all pairs

Smell alikestrong

Cooked together5,154 recipes

Shared aroma: beta-phellandrene (minty, terpene).

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

Swap the white pepper

How well each one fits the dish's main ingredients (cucumber, lemon, mace, clove, horseradish, shallot, ginger):

Allspicefits better
Turmericfits better
Cinnamonfits better
White pepperthe original

Fit is the average pairing score against cucumber, lemon, mace, clove, horseradish, shallot, ginger. Candidates are from the same food group and used in at least 100 recipes.