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Yeast
Mrs. E. S. Cheesebrough.
Put two tablespoons of hops in a muslin bag and boil them in three quarts of water for a few minutes; have ready a quart of hot mashed potatoes, put in one cup of flour, one tablespoon of sugar, one of salt; pour over the mixture the boiling hop water, strain through a colander, put a pint or less of fresh baker's yeast, or two cakes of yeast in while it is warm, and set it in a warm place to rise. This yeast will keep three or four weeks, if set in a cool place. In making it from time to time, use a bowl of the same to raise the fresh with.
This is a bread starter rather than a dish: a hopped potato barm of the kind kept going on a kitchen shelf before packaged yeast was reliable. Most of the work is temperature control.
- The hinge: temperature when you pitch"Put the yeast in while it is warm" means blood-warm, roughly 95-105F, not the boiling hop water. Anything above about 120F kills the culture and you will have a pot of sweet potato water that spoils instead of ferments.
- Quantities and yieldThree quarts of water plus a quart of mashed potato gives close to a gallon of liquid barm. That is far more than a modern household needs; a quarter batch behaves identically and fits in a jar.
- HopsWhole dried hops from a homebrew supplier are the right thing. Two tablespoons in three quarts is a light dose, used as much as a preservative as for flavour, since hop acids suppress many spoilage bacteria while leaving yeast unbothered.
- Baker's yeast, then and nowA "cake" was compressed fresh yeast, though the size varied by maker and period; the familiar small cake is about 0.6 oz, while earlier cakes were often larger. A pint of "fresh baker's yeast" means liquid barm bought from a bakery, which no longer exists as a retail item. Two small cakes of fresh yeast, or two packets of active dry, give roughly the equivalent pitch.
- PotatoesPlain boiled and mashed, no butter, no milk, no salt beyond what the recipe adds. The starch is food for the yeast; dairy in a room-temperature keeping ferment is asking for trouble.
- StrainingPass the hot mixture through the colander before it cools, while it is still loose. Once the potato sets it will not go through, and you will be pushing paste.
- "A cool place"That meant a cellar or cold pantry at 45-55F. Use the refrigerator. Even so, a week or two is a more realistic keeping time than four, and the barm should be discarded if it smells of nail varnish, turns pink, or grows any surface mould.
- Using itReckon roughly a cup of this barm in place of a packet of yeast, with a correspondingly longer, slower rise. It is thin and yeasty-smelling in use; stir before pouring, since the potato solids settle hard.
- The backslopping instructionThe last line is the point of the whole thing. Reserving a bowl of the old barm to start the next batch means you only buy commercial yeast once, which was the economy the recipe was written for.
Before packaged yeast could be trusted, households commonly kept their own leaven, and hopped potato barm was, by many accounts, among the usual North American versions: potato for starch, sugar for a quick start, salt and hops to hold off souring long enough for the jar to last between bakings. Compressed fresh yeast was becoming available in the 1870s -- Fleischmann's is generally credited with popularising it in the United States around the time of the 1876 Centennial -- and this recipe sits exactly on that hinge, buying a little commercial yeast and then propagating it indefinitely at home. The Home Cook Book was a subscription charity cookbook of contributed recipes, each signed by the woman who gave it, and Mrs. Cheesebrough's contribution is a working set of instructions from a kitchen where flour was cheap and reliable leavening was not.