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Potato Yeast (Boil one cup hops in a sack)
Boil one cup hops in a sack in two quarts water for fifteen minutes; remove sack with hops, add immediately after grating (to prevent their darkening) five good-sized Irish potatoes, peeled and grated raw, one cup white sugar, one table-spoon salt, and one of ginger; stir occasionally and cook from five to ten minutes, and it will boil up thick like starch; turn into a jar, and when just tepid in summer, or quite warm in winter, add one-half pint good yeast (always save some to start with); set jar in a large tin pan, and as often as it rises stir down until fermentation ceases, when it will be quite thin. Cover closely, and set away in a cool place, and it will keep two weeks. When yeast smells sour but does not taste sour it is still good; if it has no smell it is dead. One cup will make six. good-sized loaves. - Mrs. D. Buxton.
A perpetual bread starter of the sort every household kept before reliable packaged yeast. The whole thing hinges on temperature at the moment you add the seed yeast and on having live yeast to seed it with.
- The hinge: seed temperature"Just tepid in summer, or quite warm in winter" points to somewhere around blood heat; the recipe gives no figure, so treat any number as an estimate. Heat well short of boiling will damage the yeast you are adding and kill it outright by roughly 130-140F, leaving a batch that simply sours; the potato mash holds heat far longer than it feels like it does, so err cool and use a thermometer rather than a fingertip.
- You need starter to startThe half-pint of "good yeast" is the previous batch, which is why the recipe says to always save some. With no heirloom starter on hand, a packet of active dry yeast rehydrated in warm water will seed it, though the resulting culture will be a single commercial strain rather than whatever mixed population the jar carried when it was kept alive from batch to batch.
- Hops in a sackOne cup of dried hops, tied in cheesecloth or muslin. They contribute bitterness and, more usefully, antibacterial compounds that suppress the lactic bacteria which would otherwise turn the jar sour. Any bittering hop works; whole cones are light and bulky, so a cup amounts to only a small weight.
- Irish potatoesOrdinary white potatoes, as distinct from sweet potatoes. Five good-sized ones is somewhere in the region of 2 to 2.5 lb. Grate them straight into the hot liquid as instructed; the recipe's only stated reason is to prevent the gratings darkening.
- Sugar, salt, gingerThe sugar feeds the culture and the salt slows competing organisms. Ginger recurs in yeast recipes of this kind, though the recipe gives no reason for it; it is the one of the three you can leave out without affecting the mechanics.
- Managing the fermentThe tin pan is an overflow tray. Stir it down each time it rises, as directed, until fermentation ceases and it thins out, then keep it somewhere cold. Two weeks is the keeping time the recipe itself claims for a cool place; a modern refrigerator may hold it somewhat longer, but it weakens steadily.
- Judging the yeastThe sour-smell-but-not-sour-taste test is sound. A sharply acetic or vinegary taste means acid bacteria have taken over and the loaves will be dense and tangy; no aroma at all means no live cells.
- Yield and useAbout two quarts of thin liquid yeast, of which one cup raises six loaves. That is a considerable amount of leavening ecipe unless you bake constantly, halve the recipe or plan to give some away as households once did.
Liquid yeasts like this one were the ordinary bread leaven of nineteenth-century American kitchens, kept alive from batch to batch in a covered jar and passed between neighbours when a culture died. Hops came into them from brewing practice: brewers' barm was the classic bread yeast, and cooks who had no brewery nearby imitated its bitterness and keeping quality with boiled hops. Potato provided starch that the yeast could work on slowly, giving the jar staying power over the fortnight the recipe promises. Compressed cake yeast, generally credited to the Fleischmann brothers' work in the United States from the late 1860s, gradually made all of this unnecessary, but community cookbooks of the 1880s such as The Dixie Cook Book still print several competing yeast recipes with contributors' names attached ecipe a sign that a reliable starter was a piece of household reputation, not a commodity.