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 ↓
To Pickle Onions
Ingredients
Directions
Prepare the onions
Peel the onions until they are white.
Scald them in a mixture of strong salt and water, then remove the onions with a skimmer.
Pickle and bottle
Prepare enough boiling hot vinegar to cover the onions.
Strew whole pepper and white mustard seed over the onions, then pour the hot vinegar over the onions to cover them.
Once cold, place the onions in wide-mouthed bottles and cork them tightly.
Optionally, add 1 tablespoon of sweet oil to the bottles before corking.
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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Vinegar + mustardtop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Pepper + mustardtop 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).
-
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
- Small white button onions
- Form the main body of the pickle, staying firm and crisp once brined and covered in vinegar.
- Vinegar
- Provides the sour acidity that preserves the onions and defines the pickled flavour.
- White mustard seed
- Adds a sharp, pungent aroma and flavour that infuses into the vinegar.
The step that matters
Pour the vinegar hot and cover the onions fully. The vinegar must be boiling hot and must cover the onions completely so that the acid penetrates evenly and keeps the onions submerged, which helps preserve them and prevents spoilage at the surface.
Swap the onion
How well each one fits the dish's main ingredients (vinegar, pepper, mustard):
- Horseradishfits better
- Radishfits better
- Lettucefits better
- Onionthe original
Fit is the average pairing score against vinegar, pepper, mustard. 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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