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Liquid Yeast

A liquid yeast starter made by mashing boiled potatoes, adding flour, sugar, salt, and yeast, then fermenting.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 6 ingredients
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Why it works: Flour and sugar are a kitchen classic. They rank in the top 15% of all ingredient pairs, and cooks put them together in 92,116 recipes. Both carry phenylacetaldehyde, which smells hawthorne, honey. The science ↓

Liquid Yeast

Ingredients

Directions

Prepare the potatoes

  1. Peel and boil the potatoes in cold water until well done.

  2. Remove the potatoes from the water and mash them very fine.

Make the starter

  1. Mix in the flour, sugar, and salt.

  2. Gradually add the boiling water used for the potatoes until all is used.

  3. When lukewarm, add the yeast.

  4. Set aside to ferment in a large bowl or jar.

  5. Once fermentation stops, bottle and keep in a cool place.

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. Flour + sugartop 15% of all pairs
    Smell alikemoderate
    Cooked together92,116 recipes

    Shared aroma: phenylacetaldehyde (hawthorne, honey).

  2. Potato + flourtop 15% of all pairs
    Smell alikemoderate
    Cooked together5,355 recipes

    Shared aroma: isobutyraldehyde (malty, green).

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

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

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

What each ingredient does

Potatoes
Their starch and mash give the starter body and provide nutrients for the yeast to feed on.
Yeast
Its live cells ferment the sugars and produce the gas and flavour that make the starter active.
Sugar
Provides readily available food for the yeast, speeding up fermentation.
Flour
Adds starch that thickens the mixture and gives the yeast more material to work on.

The step that matters

Add the yeast only when lukewarm. Yeast cells are killed by very hot liquid, so the water must have cooled enough to be safe. If it is still hot, the yeast will not ferment and the starter will fail.

Swap the potato

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

  1. Arrowrootfits better
  2. Beetrootfits better
  3. Sweet potatofits better
  4. Potatothe original

Fit is the average pairing score against flour, 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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