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Liquid Yeast

A fermented liquid mixture used as yeast for baking.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 6 ingredients
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Why it works: Potato and sugar are a kitchen classic. They rank in the top 30% of all ingredient pairs, and cooks put them together in 3,032 recipes. Both carry beta-damascenone, which smells apple, rose. The science ↓

Liquid Yeast

Ingredients

Directions

Prepare the potatoes and hops

  1. Wash and peel the potatoes, then soak them in cold water for 30 minutes.

  2. In a saucepan, combine the hops and boiling water, and cook slowly for 10 minutes.

  3. Grate the potatoes and quickly add them to the boiling water, straining to remove the hops.

Make the mash

  1. Place the mixture over moderate heat, stirring constantly for 5 minutes.

  2. Remove from heat, add sugar and salt, and mix well.

  3. Transfer to a large bowl and let it cool to lukewarm.

Ferment and store

  1. Stir in the yeast, cover, and let it sit in a warm place for 4 to 5 hours until it ferments.

  2. Beat the mixture several times as it rises, then let it cool.

  3. Pour into glass jars, leaving some space at the top, and secure the lids tightly.

  4. Store the yeast in a cool place and stir well before each use.

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. Potato + sugartop 30% of all pairs
    Smell alikelow
    Cooked together3,032 recipes

    Shared aroma: beta-damascenone (apple, rose).

  2. Potato + hopstop 39% of all pairs
    Smell alikelow
    Cooked together3 recipes

    Shared aroma: myrcene (balsamic, herbaceous).

  3. Hops + sugartop 43% of all pairs
    Smell alikelow
    Cooked together6 recipes

    Shared aroma: guaiacol (smoky, sweet).

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

What each ingredient does

Potatoes
Starch that feeds the yeast and gives the liquid body.
Sugar
Provides food for the yeast so it can ferment and produce gas.
Liquid yeast
Starts fermentation, so the mixture rises and becomes active.
Dried hops
Adds bitterness and aroma, and helps preserve the liquid.

The step that matters

Cooling to lukewarm before adding the yeast. Yeast is killed by very hot liquid, so the mixture must cool to lukewarm before the yeast is stirred in. Too hot and the culture fails; too cold and fermentation is slow.

Swap the potato

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

  1. Mustardfits better
  2. Cucumberfits about as well
  3. Capsicumfits about as well
  4. Potatothe original

Fit is the average pairing score against hops, sugar. 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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