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Tomato Catsup

A thick tomato sauce made by boiling tomatoes and onions, then sieving and bottling.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 ingredients
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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 Catsup

Ingredients

Directions

  1. Boil the tomatoes and onions for 3 hours or until thick.

  2. Press the mixture through a sieve.

  3. Bottle the catsup.

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.

  1. Tomato + peppertop 7% of all pairs
    Smell alikemoderate
    Cooked together17,923 recipes

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

  2. Tomato + oniontop 8% of all pairs
    Smell alikemoderate
    Cooked together20,633 recipes

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

  3. Onion + peppertop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

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

  4. Onion + vinegartop 14% of all pairs
    Smell alikemoderate
    Cooked together18,226 recipes

    Shared aroma: acetic acid (sour, vinegar).

  5. Vinegar + peppertop 14% of all pairs
    Smell alikemoderate
    Cooked together27,814 recipes

    Shared aroma: 4'-methylacetophenone (bitter almond).

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

What each ingredient does

Tomatoes
Provide the bulk and body of the ketchup as they cook down and thicken.
Onions
Add savoury depth and body that thickens the sauce as it cooks down.
Sugar
Adds sweetness that balances the acidity of the tomatoes and vinegar.
Vinegar
Adds acidity that brightens the flavour and helps preserve the ketchup.

The step that matters

Boil until thick. Tomatoes and onions must cook long enough for water to evaporate and the pulp to thicken. Stopping early leaves a thin sauce that may spoil sooner in storage.

Swap the onion

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

  1. Capsicumfits better
  2. Cucumberfits better
  3. Mustardfits better
  4. Onionthe original

Fit is the average pairing score against tomato, sugar, vinegar, 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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