Name: Pickled Onions
Ingredients: Small silver-skinned onions; Brine (enough to float an egg); Vinegar; Mace; Whole red peppers; Coarse sea salt (formerly 'bay salt'); Ginger

Why it works: Pepper and ginger match in chemistry and in kitchens. They rank in the top 9% of all ingredient pairs, and cooks put them together in 6,800 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Pickled Onions

Ingredients

Directions

Remove the outer skin from the onions until they are white and clean.
Soak the onions in brine for 3 days.
Bring vinegar to a boil, then add a little mace and whole red peppers.
Drain the onions from the brine and pour the hot vinegar mixture over them.
For an alternative method, peel the onions and soak them in strong saltwater for 9 days, changing the water daily.
Place the soaked onions in jars and cover with boiling hot saltwater.
Once cooled, drain the onions and place them on a sieve.
Prepare vinegar by boiling white wine vinegar with a blade of mace, salt, and ginger, then pour it over the onions.

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.

Pepper + gingertop 9% of all pairs

Smell alikestrong

Cooked together6,800 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + gingertop 9% of all pairs

Smell alikemoderate

Cooked together7,595 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Onion + peppertop 11% of all pairs

Smell alikemoderate

Cooked together68,474 recipes

Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Mace + gingertop 11% of all pairs

Smell alikelow

Cooked together2,152 recipes

Shared aroma: alpha-pinene (pine, turpentine).
Onion + vinegartop 14% of all pairs

Smell alikemoderate

Cooked 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

Swap the mace

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

Turmericfits better
Garlicfits better
Allspicefits better
Macethe original

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