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Dessert

Barley Sugar

A candy made by boiling sugar, water, egg white, and lemon juice until firm, then poured onto a slab and cut into strips.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 4 ingredients
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Why it works: Sugar and lemon are a kitchen classic. They rank in the top 18% of all ingredient pairs, and cooks put them together in 53,532 recipes. Both carry 2-nonenal, which smells fatty, green. The science ↓

Barley Sugar

Ingredients

Directions

Make the syrup

  1. Dissolve the sugar in the water with the egg white.

  2. Boil until it reaches candy height.

  3. Add the lemon juice and boil quickly until it returns to its previous condition.

Shape

  1. Pour onto a marble slab.

  2. Once stiff, cut into strips and twist.

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.

  1. Sugar + lemontop 18% of all pairs
    Smell alikelow
    Cooked together53,532 recipes

    Shared aroma: 2-nonenal (fatty, green).

  2. Egg + lemontop 19% of all pairs
    Smell alikelow
    Cooked together44,316 recipes

    Shared aroma: (e,e)-2,4-decadienal (fatty, deep fried).

  3. Sugar + eggtop 21% of all pairs
    Smell alikemoderate
    Cooked together122,807 recipes

    Shared aroma: 2-nonenal (fatty, green).

Sugar and lemon barely smell alike, yet cooks put them together in 53,532 recipes: they work on texture and structure more than aroma.

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

What each ingredient does

Lump sugar
Forms the main body of the candy as it cooks down into a hard, glassy mass.
Egg white
Helps clarify the syrup, collecting impurities so the candy comes out clear.
Lemon juice
Adds acidity that helps prevent the sugar from crystallising, keeping the candy smooth.

The step that matters

Boil quickly after adding the lemon juice. Acid added to boiling sugar begins to break sucrose into glucose and fructose, which keeps the candy from turning grainy. Boiling briefly and quickly, rather than long, prevents the syrup from darkening or over-inverting before it returns to its previous state.

Swap the lemon

How well each one fits the dish's main ingredients (sugar, egg):

  1. Vanillafits better
  2. Raisinfits about as well
  3. Lemonthe original
  4. Datesfits less well

Fit is the average pairing score against sugar, egg. 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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