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Tomato Ketchup

A homemade tomato ketchup made with tomatoes, peppers, onions, salt, sugar, vinegar, and spices, simmered until thick.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 12 ingredients
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Why it works: Cinnamon and clove match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 14,189 recipes. Both carry ethyl cinnamate, which smells sweet, balsamic. The science ↓

Tomato Ketchup

Ingredients

Directions

Prepare the vegetables

  1. Chop onions and green peppers finely and cut up the tomatoes.

  2. Boil the mixture until tender, about 1 hour.

  3. Squeeze the mixture through a fruit press to remove skin and seeds.

Cook the ketchup

  1. Return the pulp to a clean kettle with sugar, salt, vinegar, and spices in a cheesecloth bag.

  2. Simmer slowly, stirring often, until slightly thick, about 15 minutes to 3 hours.

  3. For a darker ketchup, use ground spices instead.

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. Cinnamon + clovetop 1% of all pairs
    Smell alikestrong
    Cooked together14,189 recipes

    Shared aroma: ethyl cinnamate (sweet, balsamic).

  2. Clove + allspicetop 1% of all pairs
    Smell alikestrong
    Cooked together7,874 recipes

    Shared aroma: estragole (anise, licorice).

  3. Cinnamon + allspicetop 1% of all pairs
    Smell alikestrong
    Cooked together5,536 recipes

    Shared aroma: estragole (anise, licorice).

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

    Shared aroma: ethyl octanoate (fruity, wine).

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

    Shared aroma: estragole (anise, licorice).

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

What each ingredient does

Ripe tomatoes
Form the bulk of the sauce and provide its base flavor and liquid.
Brown sugar
Adds sweetness and helps balance the sharpness of the vinegar.
Vinegar
Provides acidity that gives ketchup its tang and helps preserve it.
Onions
Add savory depth and body as they soften during boiling.

The step that matters

Simmer slowly, stirring often. Long, gentle simmering evaporates water and thickens the pulp into ketchup. Heating too hard or leaving it unstirred can scorch the sugars and sticking solids on the bottom of the kettle, giving a burnt taste.

Swap the onion

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

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

Fit is the average pairing score against tomato, pepper, sugar, vinegar, cinnamon, clove, 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.

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