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Potato Yeast Without Hops
Four good-sized potatoes peeled, boiled and mashed, four tablespoons white sugar, one of ginger, one of salt, two cups flour; pour over this a pint of boiling water, and beat till all the lumps disappear. After it has cooled, add to it one cup good yeast, and set away to rise; when risen put in glass or stone jar, cover and set away in a cool place. - Mrs. George H. Rust, Minneapolis, Minn.
This is a barm, or wet yeast starter, of the sort a household kept going from one baking to the next. It is not a bread recipe; it produces roughly a quart of liquid leaven to be measured into doughs.
- What "good yeast" meansThe one cup of yeast called for is a cup of an existing, actively working yeast, borrowed from a previous batch or a neighbour. Without one the mixture will not reliably rise, and a modern baker wanting a potato ferment can start it with a teaspoon or two of commercial dry yeast.
- QuantitiesFour good-sized potatoes is about 1 1/2 lb, mashed smooth with no butter or milk. A pint of boiling water is 2 cups; the tablespoon measures give roughly 4 tablespoons sugar, 1 tablespoon ground ginger and 1 tablespoon salt.
- Why the gingerGinger turns up repeatedly in nineteenth-century yeast recipes; it was held to quicken fermentation, and it may also help cover the sour or off flavours that come from stray bacteria, as well as the flatness of a potato base.
- The hinge: let it cool firstThe boiling water is poured over the flour and potato to scald the mixture and thicken it. Adding the starter before it has cooled to lukewarm, no more than about 100F, kills the yeast and the batch simply sours.
- Rising timeExpect 6 to 12 hours at ordinary warm room temperature, until it is foamy and smells sharply of beer. "Set away in a cool place" meant a cellar or springhouse; a refrigerator is the modern equivalent, and the ferment keeps a week or so before it needs feeding again.
- VesselUse glass or glazed stoneware as directed, scalded first, and cover loosely rather than sealing it. A tightly closed jar of active ferment builds pressure.
- Using itA cup of this liquid yeast can take the place of packaged yeast in a bread dough, with the flour and water in the recipe reduced to account for what the starter brings; the working amount is a matter of trial. Doughs raised on it are slower than modern quick-rise breads.
- When to throw it outPink or orange streaks or fuzzy mould mean the culture has been overtaken; discard it. A smell of cheese is likewise a bad sign, while a sharp acetone note usually means only that the ferment is hungry.
Before packaged yeast, a cook's leaven was a household possession, kept alive on the same shelf as the bread crock and shared along a street when someone let theirs die. Many nineteenth-century yeasts were built on hops, boiled for their bitterness and mild antiseptic effect, which is why this recipe advertises itself by what it leaves out: potato, sugar and ginger will carry a ferment on their own, and the starch of a boiled potato feeds it well. Buckeye Cookery (1877, compiled from contributed recipes of Ohio and Midwestern housewives) devotes a whole short section to yeast for exactly this reason, gathering several competing methods under the names of the women who vouched for them. Within a generation the argument was largely settled by commercial compressed yeast, sold in foil-wrapped cakes and reliable in a way no kitchen barm could be, and recipes like Mrs. Rust's dropped out of general cookbooks.