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 soup
Boil the tomatoes and onion in water for 30 minutes.
Add salt, pepper, sugar, butter, and flour; mix until smooth like thin cream.
Boil for 10 minutes.
Boil the milk separately.
Finish and serve
When both are boiling, pour the milk into the tomatoes to prevent curdling.
Serve with squares of toasted bread.
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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Flour + buttertop 12% of all pairsAroma overlaplowMentioned together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
Flour and butter 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
- Form the body and main flavour of the soup as they cook down.
- Flour
- Thickens the soup so it becomes smooth and creamy.
- Butter
- Adds fat for richness and a smoother mouthfeel.
- Milk
- Adds creaminess and mellows the acidity of the tomatoes.
- Sugar
- Balances the acidity of the tomatoes with a touch of sweetness.
The step that matters
Pouring the milk into the tomatoes. Milk is prone to curdling when it meets acidic tomatoes. Boiling the milk separately and pouring it in while both are hot, as the step directs, helps keep it smooth. Adding it cold or to a cooler pot raises the risk of curdling.
Flavor stand-ins for the onion
How well each one fits the dish's main ingredients (tomato, flour, butter, sugar, pepper, milk):
- Capsicumbetter flavor fit
- Potatobetter flavor fit
- Sweet potatobetter flavor fit
- Onionthe original
Fit is the average pairing score against tomato, flour, butter, sugar, pepper, 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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