Name: Cold Catsup
Ingredients: 1 peck tomatoes; 1 quart wine vinegar; 1 red pepper; 2 tablespoons black mustard seed; 3 tablespoons yellow mustard seed; grated horseradish to taste; coarse sea salt to taste; cayenne pepper 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 ↓

Cold Catsup

Ingredients

Directions

Prepare the tomatoes

Pare and finely chop the tomatoes without scalding them.
Drain the chopped tomatoes.

Combine and season

In a bowl, combine the drained tomatoes with wine vinegar, red pepper, black mustard seed, yellow mustard seed, grated horseradish, coarse sea salt, and cayenne pepper. Mix well and adjust seasoning to taste.

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).
Tomato + peppertop 7% of all pairs

Smell alikemoderate

Cooked together17,923 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Vinegar + mustardtop 7% of all pairs

Smell alikemoderate

Cooked together14,067 recipes

Shared aroma: isobutyraldehyde (malty, green).
Pepper + mustardtop 9% of all pairs

Smell alikemoderate

Cooked together15,430 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Tomato + winetop 10% of all pairs

Smell alikemoderate

Cooked together2,759 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

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

What each ingredient does

Tomatoes: Provide the main body and bulk of the catsup.
Wine vinegar: Adds acidity that gives the catsup its tangy bite and helps keep it fresh.
Mustard seed: Adds sharp, pungent heat and aroma as the seeds release flavor when mixed with liquid.
Horseradish: Adds a sharp, pungent heat that complements the tomatoes and mustard.

Swap the tomato

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

Shallotfits better
Radishfits better
Broccolifits better
Tomatothe original

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