Name: Oil Pickles
Ingredients: 3 pints small onions; 2 cups olive oil; 1 lump alum (size of an egg); Cold vinegar to cover; 1 cup white pepper; 1 cup mustard seed; Coarse sea salt

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 ↓

Oil Pickles

Ingredients

Directions

Slice the small onions and place them in a bowl with coarse sea salt. Let them stand for three hours.
Drain the onions and layer them with cucumbers in a jar.
Dissolve the alum in vinegar and pour it over the cucumbers and onions.
Add the white pepper and mustard seed in small bags through the pickles.
Cover everything with olive oil and additional vinegar.

Recipe from a historical cookbook (Internet Archive).

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.

Onion + mustardtop 6% of all pairs

Smell alikestrong

Cooked together9,259 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Vinegar + mustardtop 7% of all pairs

Smell alikemoderate

Cooked together14,067 recipes

Shared aroma: isobutyraldehyde (malty, green).
Olive + mustardtop 8% of all pairs

Smell alikestrong

Cooked together5,950 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Onion + olivetop 8% of all pairs

Smell alikemoderate

Cooked together29,779 recipes

Shared aroma: 2,4-decadienal (seaweed).
Olive + vinegartop 10% of all pairs

Smell alikemoderate

Cooked together12,297 recipes

Shared aroma: isoamyl acetate (banana, fruity).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

Swap the white pepper

How well each one fits the dish's main ingredients (onion, olive, egg, vinegar, mustard):

Capersfits better
Garlicfits better
Tarragonfits better
White pepperthe original

Fit is the average pairing score against onion, olive, egg, vinegar, mustard. Candidates are from the same food group and used in at least 100 recipes.