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 or Soy
Ingredients
Directions
Make the ketchup
Combine tomatoes, mustard, salt, ground black pepper, allspice, and red pepper.
Simmer the mixture for three hours.
Strain through a sieve.
Add one quart of vinegar.
Simmer ten minutes longer.
Bottle and store
Pour into small bottles.
Cork tightly.
Keep in a cool place.
Nutrition, whole recipe (rough)
What these numbers assume: 5 portions
| Ingredient | Portion assumed | kcal |
|---|---|---|
| Tomato | 1 medium (123g) | 22 |
| Chili | 1 tsp (2.7g) | 8 |
| Vinegar | 1 tbsp (15ml) distilled | 3 |
| Mustard | 1 tsp (5g) yellow | 3 |
| Salt | 1 tsp (6g) | 0 |
One typical portion per ingredient; the recipe's quantities are not counted. A rough guide only, not for medical or dietary planning.
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. See the original page.
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.
-
Tomato + peppertop 7% of all pairsSmell alikemoderateCooked together17,923 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Vinegar + mustardtop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Mustard + peppertop 9% of all pairsSmell alikemoderateCooked together15,430 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Tomato + mustardtop 11% of all pairsSmell alikemoderateCooked together2,482 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Vinegar + peppertop 14% of all pairsSmell alikemoderateCooked 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
- Form the bulk of the sauce and provide its body, sweetness and tomato flavor.
- Mixed mustard
- Adds sharp, pungent flavor that balances the sweetness of the tomatoes.
- Vinegar
- Adds acidity that sharpens the flavor and helps preserve the ketchup.
- Red pepper
- Adds heat and a pungent, warming note to the sauce.
The step that matters
Simmer for three hours, then add the vinegar and simmer ten minutes longer. Long simmering thickens the tomato mixture by evaporating water and concentrates its flavor. Adding vinegar after the long simmer keeps its sharp acidity bright, since extended heating can dull it.
Swap the tomato
How well each one fits the dish's main ingredients (vinegar, mustard, pepper):
- Horseradishfits better
- Radishfits better
- Lettucefits better
- Tomatothe original
Fit is the average pairing score against vinegar, mustard, 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.
More tomato ketchup recipes
You might also like
Tomato Soup526 recipes
Cream of Tomato Soup107 recipes
Tomato Bisque61 recipes
Cream Tomato Soup28 recipesThe free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.
Prefer an account? Create a free account to save pairings and unlock the full chemistry.