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Potato Yeast
Take five or six potatoes; grate fine. Then add two tablespoonfuls of sugar and one of salt. Take one quart of water and a handful of hops. Boil a few minutes, strain and stir into potatoes. Set on the stove and stir until thick. When cool add one cup of yeast.
A potato-and-hop yeast, the kind of perpetual starter a household kept going from one batch to the next. It works, but it depends on one thing the text does not explain: the cup of yeast at the end has to come from somewhere.
- The cup of yeastThis is the hinge. The recipe does not create yeast from nothing; it feeds an existing culture, and the cup was taken from the previous batch of the same brew. Starting from scratch, a packet of active dry yeast slurried in a little warm water, or a cup of active sourdough starter, will seed it.
- Cool means under 110FCool means blood-warm -- "When cool" is not optional wording. Let the cooked potato mash drop to about 100-110F before the yeast goes in; much above that the culture is progressively damaged, and by about 140F it is dead and you get nothing but sour potato paste.
- HopsA handful of dried hop flowers, sold by weight at any homebrew supplier; a quarter to half an ounce is a fair guess at the quantity. They are there as a mild antiseptic to hold back competing bacteria, and for bitterness that keeps the batch from going sour quickly. Whole flowers, not pellets, are easier to strain.
- PotatoesFive or six medium potatoes, call it 1.5 lb. Use starchy russets; waxy varieties give a thin, slack mash that will not thicken as described.
- "Stir until thick"The grated potato and hop water cook down to something like a loose wallpaper paste, a few minutes over medium heat. It thickens suddenly once the starch gelatinises, and it scorches just as suddenly, so keep it moving and take it off the moment it stiffens.
- Fermenting and keepingCover loosely and leave at room temperature until it is foamy and smells sharply of beer, usually 12 to 24 hours, then refrigerate. It keeps a week or so and needs to be re-fed to survive longer.
- Yield and strengthThe quart makes enough for several bakings; figure about a cup of this liquid yeast for a two-loaf batch of bread. It is far weaker than commercial yeast, so doughs raised with it take several hours and often an overnight rise.
- Reserve before you bakeSet aside a cup before using any of it, or the chain breaks. That habit is why the book can end the recipe with "add one cup of yeast" and expect no questions.
Before packaged yeast was reliably available, many American households kept a liquid yeast alive on the pantry shelf, and potato-and-hop versions appear frequently in nineteenth-century and early twentieth-century cookbooks. The potato supplies starch and sugar the yeast can eat, the hops act as a preservative borrowed from brewing practice, and the salt and sugar season and feed the culture. Such recipes are always circular, assuming a previous batch, because in practice a starter came from a neighbour or a relative and was simply kept going. Fleischmann's compressed yeast had been sold in the United States since the 1870s, but distribution was uneven and rural cooks kept making their own for decades after, which is why a book of this vintage prints the method without a word of introduction.