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 ↓
Cream of Tomato Soup
Ingredients
Directions
Make the tomato base
Combine tomatoes, onion, and green pepper in a saucepan.
Cook slowly for about 10 minutes.
Strain the mixture to remove solids.
Add bicarbonate of soda to the tomato juice.
Make the white sauce
Rub flour and butter together in a separate bowl until smooth.
Add the flour-butter mixture to the milk and stir over medium heat until it thickens slightly.
Combine and serve
Pour the milk mixture into the tomato juice just before serving.
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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Onion + peppertop 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
- Butter
- Enriches the sauce with fat and helps the flour thicken it smoothly.
- Flour
- Thickens the milk into a smooth, body-rich sauce that gives the soup its creaminess.
- Milk
- Forms the creamy base of the soup and, when heated with flour, thickens into a sauce.
- Tomatoes
- Provide the main flavour and acidity, and the juice forms the soup's base.
- Bicarbonate of soda
- Neutralises some of the tomato's acidity, reducing sharpness and helping prevent curdling.
The step that matters
Pour the milk mixture into the tomato juice just before serving. Tomato acid can cause hot milk to curdle or separate. Adding the milk at the last moment, with the tomato juice already neutralised by bicarbonate of soda, helps keep the soup smooth.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, butter, pepper, flour, milk):
- Capsicumbetter flavor fit
- Potatobetter flavor fit
- Okrabetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, butter, pepper, 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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