Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Pickled Onions
Ingredients
Directions
Prepare
Pare the onions and soak them in salt water overnight.
In a pot, combine mustard seed and black pepper.
Pickle
Boil the vinegar and pour it over the onions.
Let the mixture stand for a few days.
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.
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.
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Onion + mustardtop 6% of all pairsSmell alikestrongCooked together9,259 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Mustard + vinegartop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Mustard + peppertop 9% of all pairsSmell alikemoderateCooked together15,430 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + vinegartop 14% of all pairsSmell alikemoderateCooked together18,226 recipes
Shared aroma: acetic acid (sour, vinegar).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- The main vegetable being pickled; it absorbs the vinegar and spices as it stands.
- Vinegar
- Provides acidity that sharpens the flavour and helps preserve the onions.
- Mustard seed
- Adds a sharp, pungent flavour to the pickling liquid.
- Black pepper
- Adds a warm, sharp aroma and gentle heat to the pickle.
The step that matters
Let the mixture stand for a few days. The acid from the vinegar and the spices need time to penetrate the onions. Rushing this step leaves the flavour sharp on the surface and underdeveloped inside.
Swap the onion
How well each one fits the dish's main ingredients (mustard, pepper, vinegar):
- Horseradishfits better
- Radishfits better
- Lettucefits better
- Onionthe original
Fit is the average pairing score against mustard, pepper, vinegar. 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.
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