Name: Lemon Pickle or Catsup
Ingredients: 6 small lemons; 3 ounces coarse sea salt; 2 ½ ounces finely-scraped horseradish; 2 ounces shallots or 1 ½ ounces garlic; 1 ½ pints boiling vinegar; ½ ounce bruised ginger; ¼ ounce whole white pepper; 2 blades of mace

Why it works: Horseradish and shallot match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 376 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Lemon Pickle or Catsup

Ingredients

Directions

Prepare the lemons

Divide the lemons into quarters and remove all visible seeds.
Sprinkle the salt over the lemons and let them sit for a week, turning occasionally.
After a week, place the lemons in a stone jar with their liquid.

Make the pickle

In a saucepan, simmer the vinegar with ginger, whole white pepper, and mace for 2-3 minutes.
Pour the hot vinegar mixture over the lemons in the jar.
Let the pickle sit for 2-3 months before using, but it can be stored for up to 4-5 months before straining.

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.

Horseradish + shallottop 1% of all pairs

Smell alikestrong

Cooked together376 recipes

Shared aroma: coumarin (sweet, hay).
Lemon + gingertop 5% of all pairs

Smell alikestrong

Cooked together5,154 recipes

Shared aroma: beta-phellandrene (minty, terpene).
Lemon + shallottop 6% of all pairs

Smell alikestrong

Cooked together2,523 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Shallot + gingertop 7% of all pairs

Smell alikemoderate

Cooked together565 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Lemon + horseradishtop 9% of all pairs

Smell alikestrong

Cooked together1,155 recipes

Shared aroma: coumarin (sweet, hay).

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

What each ingredient does

Lemons: Provide the sour, aromatic base that softens and flavours the pickle as it cures.
Coarse sea salt: Draws liquid out of the lemons and helps preserve them during the week-long salting.
Horseradish: Adds pungent heat that mellows over the long resting period.
Boiling vinegar: Acidity that preserves the lemons and sharpens the final pickle.

The step that matters

Pouring the hot vinegar over the lemons. The vinegar must be simmered briefly and poured while hot so the spices release flavour and the acid penetrates the lemons. Cooling it first weakens the infusion and the preservation.

Swap the white pepper

How well each one fits the dish's main ingredients (lemon, horseradish, shallot, vinegar, ginger, mace):

Tarragonfits better
Allspicefits better
Turmericfits better
White pepperthe original

Fit is the average pairing score against lemon, horseradish, shallot, vinegar, ginger, mace. 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.

Lemon Sauce236 recipes

Horseradish Sauce17 recipes

Tomato Soup526 recipes

Brown Bread461 recipes

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Lemon Pickle or Catsup