Name: Cold Tomato Catsup
Ingredients: 1 peck tomatoes; 3 pints vinegar; 1 teacup coarse sea salt; 1 teacup mustard seed, pounded; 4 pods red pepper, broken up; 3 tablespoons black pepper; 1 small cup celery seed; 2 pieces horseradish, cut up; 1 cup nasturtium seed, cut up fine

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

Prepare the tomatoes

Pare the tomatoes and remove the water and seeds.
Cut the pulp finely.

Make the ketchup

In a large bowl, combine the tomatoes with vinegar, salt, mustard seed, red pepper, black pepper, celery seed, horseradish, and nasturtium seed. Mix well.
Bottle and seal.

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: Form the bulk of the ketchup and provide its body and main flavor.
Vinegar: Adds acidity that sharpens flavor and helps preserve the ketchup.
Mustard seed: Contributes pungent, sharp flavor that balances the sweetness of the tomatoes.
Celery seed: Adds a savory, aromatic flavor note.
Horseradish: Adds sharp, pungent heat that gives the sauce its bite.

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.