Name: Tomato Catsup
Ingredients: 1 gallon of tomatoes (after the first straining); 1 quart of vinegar; 3 tablespoons of salt; 2 tablespoons of black pepper; 4 tablespoons of mustard seed; 3 pods of red peppers; ⅓ tablespoon of allspice

Why it works: Mustard and allspice match in chemistry and in kitchens. They rank in the top 2% of all ingredient pairs, and cooks put them together in 1,928 recipes. Both carry methyleugenol, which smells clove, spice. The science ↓

Tomato Catsup

Ingredients

1 gallon of tomatoes (after the first straining)
1 quart of vinegar
3 tablespoons of salt
2 tablespoons of black pepper
4 tablespoons of mustard seed
3 pods of red peppers
⅓ tablespoon of allspice

Directions

Boil the tomatoes until thick.
Add mustard seed and red peppers when cooking the tomatoes to avoid straining twice.
Optionally, add celery seed if desired.
Store in a cool place; it will keep well.

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 + allspicetop 2% of all pairs

Smell alikestrong

Cooked together1,928 recipes

Shared aroma: methyleugenol (clove, spice).
Pepper + allspicetop 5% of all pairs

Smell alikestrong

Cooked together6,395 recipes

Shared aroma: estragole (anise, licorice).
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).

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, once boiled down, give it body and a rich flavour.
Vinegar: Adds acidity that gives the ketchup its tang and helps preserve it.
Mustard seed: Contributes a pungent, slightly sharp aroma and background heat to the sauce.
Red peppers: Add warmth and a gentle pepper bite to the flavour.

Swap the tomato

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

Horseradishfits better
Radishfits better
Shallotfits better
Tomatothe original

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