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Tomato Ketchup

A preserved tomato ketchup made from ripe tomatoes, sweet pepper, onions, spices, sugar, vinegar, and salt.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 12 ingredients
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Why it works: Allspice and clove match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 7,874 recipes. Both carry estragole, which smells anise, licorice. The science ↓

Tomato Ketchup

Ingredients

Directions

Prepare

  1. Select red ripe tomatoes, discarding any green or yellowish parts.

  2. Chop the sweet red pepper and onions.

  3. Add the chopped pepper and onions to the tomatoes.

  4. Cook the tomatoes thoroughly.

  5. Strain the cooked tomatoes through a colander to save the pulp.

Make the ketchup

  1. For every gallon of pulp, add salt, sugar, mustard powder, vinegar, whole spices, and sliced red peppers.

  2. Cook for 1.5 hours until nearly thick. Add vinegar. Cook until thick.

Bottle and seal

  1. Pour the ketchup into hot sterilized bottles.

  2. If selling, process the bottles in hot water for 30 minutes, then seal tightly.

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. Allspice + clovetop 1% of all pairs
    Smell alikestrong
    Cooked together7,874 recipes

    Shared aroma: estragole (anise, licorice).

  2. Mustard + allspicetop 2% of all pairs
    Smell alikestrong
    Cooked together1,928 recipes

    Shared aroma: methyleugenol (clove, spice).

  3. Pepper + clovetop 5% of all pairs
    Smell alikestrong
    Cooked together17,451 recipes

    Shared aroma: ethyl octanoate (fruity, wine).

  4. Pepper + allspicetop 5% of all pairs
    Smell alikestrong
    Cooked together6,395 recipes

    Shared aroma: estragole (anise, licorice).

  5. Onion + mustardtop 6% of all pairs
    Smell alikestrong
    Cooked together9,259 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

Red ripe tomatoes
Form the bulk of the ketchup and provide its main body and flavour once cooked and strained.
Sugar
Adds sweetness that balances the acidity of the tomatoes and vinegar.
Vinegar
Adds acidity that gives the ketchup its tang and helps preserve it.
Onions
Add savoury depth and aroma as they cook down into the tomato base.
Sweet red pepper
Adds mild sweetness and fresh vegetable flavour to the cooked base.

The step that matters

Cooking down until thick. Ketchup thickens only as water evaporates during the long simmer. Stopping early leaves it thin and watery, while the acid and sugar keep building flavour as it reduces.

Swap the tomato

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

  1. Horseradishfits better
  2. Shallotfits better
  3. Capsicumfits better
  4. Tomatothe original

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