Why it works: Butter and milk are a kitchen classic. They rank in the top 7% of all ingredient pairs, and 81,283 recipes mention both. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓
Tomato Soup
Ingredients
Directions
Make the tomato base
Stew the tomatoes until soft.
Strain the tomatoes through a soup strainer to remove seeds.
Measure 1 pint of the liquid.
Add salt, pepper, baking soda, and onion to the liquid.
Heat the mixture slowly on the stove.
Make the white sauce
Heat the milk in a separate saucepan.
Melt the butter in another pan.
Stir in the flour until bubbly.
Gradually add the heated milk to the butter and flour mixture.
Stir until smooth.
Combine and serve
Combine the tomato liquid with the white sauce.
Strain the combined mixture again.
Return the mixture to heat.
Serve as soon as steaming hot.
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.
Photo for illustrative purposes only · Contact us to use it
Explore the science
The flavor team
The pairs that carry this dish. Each one is judged two ways: how much aroma chemistry they share, and how many recipes mention both.
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Butter + milktop 7% of all pairsAroma overlapmoderateMentioned together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Tomato + peppertop 7% of all pairsAroma overlapmoderateMentioned together17,923 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Tomato + oniontop 8% of all pairsAroma overlapmoderateMentioned together20,633 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Pepper + oniontop 11% of all pairsAroma overlapmoderateMentioned together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + flourtop 12% of all pairsAroma overlaplowMentioned together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
Butter and flour share little aroma chemistry, yet 124,287 recipes mention both: they likely work on texture and structure more than aroma.
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, flavor, and liquid of the soup.
- Milk
- Forms the creamy base of the white sauce, adding richness and smoothness.
- Butter
- Adds fat and flavor to the white sauce and carries the flour.
- Flour
- Thickens the butter and milk into a smooth white sauce.
- Baking soda
- Neutralizes some tomato acidity, which keeps the soup from curdling with milk.
The step that matters
Combine the tomato liquid with the white sauce. Tomato acid can curdle hot milk. Keeping the mixture hot but not boiling, and serving promptly, helps it stay smooth.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, pepper, butter, flour, milk):
- Capsicumbetter flavor fit
- Potatobetter flavor fit
- Okrabetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, pepper, butter, flour, milk. Candidates are from the same food group and used in at least 100 recipes. This compares flavor only: it does not check the job the ingredient does in the dish (bulk, moisture, acidity, structure).
“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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