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Tomato Ketchup

A preserved tomato condiment made with tomatoes, peppers, 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 the tomatoes

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

  2. Chop the sweet red pepper and onions, then add them to the tomatoes.

  3. Cook the tomatoes thoroughly, then strain through a colander to save the pulp.

Make the ketchup

  1. For every gallon of pulp, add salt, sugar, mustard powder, vinegar, and whole spices in a spice bag.

  2. Cook for 1.5 hours until nearly thick, then add vinegar and cook until thick.

Bottle and process

  1. Pour the ketchup into hot sterilized bottles.

  2. If selling, process the hot bottles in boiling 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
Provide the main body, moisture and tomato flavor of the ketchup.
Onions
Add savory depth and aroma as they soften during long cooking.
Sugar
Adds sweetness that balances the acidity of the tomatoes and vinegar.
Vinegar
Adds acidity for tang and helps preserve the finished ketchup.
Sweet red pepper
Contributes sweetness and fresh pepper flavor to the tomato base.

The step that matters

Cooking down the pulp to thick. Long simmering evaporates water and concentrates the tomato solids, so the ketchup thickens. Stopping too early leaves it thin and watery, while overcooking can scorch the sugars on the bottom of the pot.

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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