Name: Cucumber Catsup
Ingredients: 12 full grown cucumbers, peeled; 12 onions; Salt, to taste; Spices, to taste; Mustard, to taste; Turmeric, to taste; Sugar, to taste (optional); Horseradish, to taste (optional); Vinegar, to taste

Why it works: Mustard and horseradish match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,832 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Cucumber Catsup

Ingredients

Directions

Prepare

Grate the cucumbers and let them drain in a sieve.
Grate the onions and combine them with the cucumbers in a large bowl.

Season and bottle

Mix thoroughly and add salt, spices, mustard, turmeric, and optional sugar and horseradish.
Add vinegar until the mixture is sufficiently wet for bottling.

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.

Mustard + horseradishtop 1% of all pairs

Smell alikestrong

Cooked together1,832 recipes

Shared aroma: coumarin (sweet, hay).
Cucumber + horseradishtop 2% of all pairs

Smell alikestrong

Cooked together640 recipes

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

Smell alikestrong

Cooked together2,279 recipes

Shared aroma: guaiacol (smoky, sweet).
Cucumber + mustardtop 3% of all pairs

Smell alikestrong

Cooked together2,281 recipes

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

Smell alikestrong

Cooked together437 recipes

Shared aroma: coumarin (sweet, hay).

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

What each ingredient does

Cucumbers: Make up the bulk of the ketchup and give it its fresh, watery body.
Onions: Add pungency and savoury depth that balances the cucumber's mild flavour.
Vinegar: Adds acidity that sharpens the flavour and helps preserve the mixture for bottling.
Mustard: Contributes sharp, pungent flavour that rounds out the seasoning.

“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.