Why it works: Milk and butter 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
Combine stewed tomatoes and baking soda in a pot; stir until foaming stops.
Add boiling water and milk, then strain the mixture.
Return the strained mixture to the stove and heat until near boiling.
Dissolve cornstarch in a little cold milk, then add to pot.
Stir in butter, salt, and pepper to taste.
If using, add onion and simmer, stirring occasionally to prevent burning.
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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Milk + buttertop 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 + oniontop 15% of all pairsAroma overlapmoderateMentioned together42,912 recipes
Shared aroma: decanal (soap, orange peel).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Stewed tomatoes
- Provide the main body, acidity and flavor of the soup.
- Baking soda
- Neutralizes tomato acidity, reducing foaming-free curdling risk and softening the tomato's sharp taste.
- Milk
- Adds creaminess and a smooth, mellow body to the soup.
- Cornstarch
- Thickens the soup as it heats, giving it a smoother, fuller texture.
- Butter
- Adds richness and a silky mouthfeel at the end.
The step that matters
Adding the baking soda to the tomatoes. Baking soda reacts with the tomato acid and releases carbon dioxide, causing vigorous foaming. Stirring until the foaming stops, before adding liquids, keeps the pot from overflowing and lets the acid be neutralized before the milk is added, which helps prevent curdling.
Flavor stand-ins for the onion
The recipe marks onion as optional. How well each one fits the dish's main ingredients (tomato, milk, butter, pepper):
- Capsicumbetter flavor fit
- Potatobetter flavor fit
- Carrotabout as good a flavor fit
- Onionthe original
Fit is the average pairing score against tomato, milk, butter, pepper. 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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