Why it works: Tomato and pepper are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 17,923 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Tomato Catchup
Ingredients
Directions
Prepare the tomatoes
Pick the stems from the tomatoes.
Wipe the tomatoes with a clean towel dipped in warm water.
Place the tomatoes in a kettle, layering them with coarse sea salt, without adding water.
Boil the tomatoes.
Skim and stir the boiling tomatoes frequently for 1 hour.
Strain the mixture through a colander.
Strain the mixture through a coarse sieve.
Make the ketchup
Add the chopped onions, mace, and black pepper to the strained liquid.
Boil the liquid for 1.5 hours.
Add more salt if necessary.
Slice the tomatoes for a thinner catchup.
Squeeze the sliced tomatoes through a linen bag.
Pound the spices.
Chop the onions very fine.
Add a little Cayenne if desired.
Bottle and store
Fill small bottles completely.
Cork the bottles tightly.
Store the bottles on their sides in a cool closet.
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.
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Tomato + peppertop 7% of all pairsSmell alikemoderateCooked together17,923 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Tomato + oniontop 8% of all pairsSmell alikemoderateCooked together20,633 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Mace + peppertop 16% of all pairsSmell alikelowCooked together12,257 recipes
Shared aroma: myristicin (spice, warm).
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Onion + macetop 17% of all pairsSmell alikelowCooked together7,078 recipes
Shared aroma: eugenol (clove, spicy).
Mace and pepper barely smell alike, yet cooks put them together in 12,257 recipes: they work on texture and structure more than aroma.
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Fully ripe tomatoes
- Provide the main body, acidity and flavour of the ketchup.
- Onions
- Add savoury depth and aroma as they cook down into the sauce.
- Whole black pepper
- Adds warm, pungent aroma that carries through the long boil.
The step that matters
Boil the liquid for 1.5 hours. Long simmering reduces water and concentrates flavour and body. Too little reduction leaves the ketchup thin and watery, and it may spoil sooner in storage.
Swap the mace
How well each one fits the dish's main ingredients (tomato, onion, pepper):
- Garlicfits better
- Cuminfits better
- Thymefits better
- Macethe original
Fit is the average pairing score against tomato, onion, pepper. 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.
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