Name: Cold Tomato Catsup
Ingredients: ½ peck tomatoes; 3 pints good vinegar; ¾ cup coarse sea salt; ¾ cup ground mustard seed; 3 peppers; handful celery seed; 1 tablespoon grated horseradish

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 ↓

Cold Tomato Catsup

Ingredients

Directions

Chop the tomatoes and combine them with vinegar, salt, mustard seed, peppers, celery seed, and horseradish in a large bowl, then mix well until all ingredients are thoroughly combined.
Transfer the mixture into bottles and seal tightly.

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).
Mustard + celerytop 2% of all pairs

Smell alikemoderate

Cooked together4,169 recipes

Shared aroma: guaiacol (smoky, sweet).
Tomato + celerytop 4% of all pairs

Smell alikemoderate

Cooked together3,377 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Pepper + celerytop 5% of all pairs

Smell alikestrong

Cooked together16,012 recipes

Shared aroma: 4'-methylacetophenone (bitter almond).
Celery + horseradishtop 6% of all pairs

Smell alikemoderate

Cooked together835 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

Tomatoes: Provide the bulk, body and fresh tomato flavor of the ketchup.
Vinegar: Adds sharp acidity that balances the tomatoes and gives the ketchup its tang.
Ground mustard seed: Contributes pungent, sharp flavor that deepens the overall seasoning.
Celery seed: Adds a warm, savory aroma that rounds out the flavor.
Horseradish: Adds a sharp, pungent bite that lifts the flavor.
Peppers: Add heat and savory depth to the sauce.

Swap the tomato

How well each one fits the dish's main ingredients (vinegar, mustard, pepper, celery, horseradish):

Lettucefits better
Broccolifits better
Radishfits better
Tomatothe original

Fit is the average pairing score against vinegar, mustard, pepper, celery, horseradish. 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.