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Itomato Catsup

A homemade tomato ketchup made by boiling tomatoes and onions, then seasoning with salt, pepper, mustard, red pepper, and brown sugar.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 ingredients
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Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Itomato Catsup

Ingredients

Directions

Prepare

  1. Slice the tomatoes and onions.

Make the ketchup

  1. Boil the sliced tomatoes and onions until soft.

  2. Strain the mixture and add the salt, white pepper, mustard, red pepper, and brown sugar.

  3. Boil down the mixture until it reduces to one third of its original volume.

  4. Once cool, adjust seasoning to taste and thin it enough to pour into bottles.

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

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

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

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

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

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

  4. Mustard + peppertop 9% of all pairs
    Smell alikemoderate
    Cooked together15,430 recipes

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

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

Tomatoes
Provide the main body, moisture and tangy flavour of the ketchup.
Onions
Add savoury depth and sweetness as they soften during boiling.
Brown sugar
Adds sweetness and helps balance the acidity of the tomatoes.
Mustard
Adds sharp, pungent flavour that complements the tomatoes.

The step that matters

Boil down the mixture to one third of its original volume. Reducing concentrates the flavour and thickens the ketchup as water evaporates. Stopping early leaves it thin and watery, while over-reducing makes it too thick and can scorch the sugars on the bottom of the pot.

Swap the white pepper

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

  1. Garlicfits better
  2. Celeryfits better
  3. Capersfits better
  4. White pepperthe original

Fit is the average pairing score against tomato, onion, mustard, pepper, sugar. 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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