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Koumiss
Dissolve two tablespoonfuls of sugar in twelve tablespoonfuls of hot water, add a quarter of a yeast cake, and to this a quart of milk, stir well, bottle, put on patent stopper and shake. Let it stand in a warm room four hours in summer and six in winter. Then place on ice. Will keep three or four days.
This is a pharmacy-era imitation koumiss: sweetened milk inoculated with baker's yeast and sealed under pressure. The method has two independent problems, and neither is fixed by adjusting the timing.
- No acidifying cultureGenuine koumiss and modern kefir rely on lactic acid bacteria that drop the pH quickly and keep spoilage organisms out. A quarter of a yeast cake supplies only Saccharomyces, which produces alcohol and gas but very little acid. Sweetened milk held warm for four to six hours with no acid barrier is a growth medium, not a preserve.
- The warm holdFour hours in a warm summer room puts a quart of milk squarely in the range where Salmonella, Listeria and Staphylococcus aureus multiply. Staph in particular leaves behind a heat-stable toxin that later chilling does nothing to remove. The instruction to keep the result three or four days compounds the exposure.
- The sealed bottleA patent stopper — the wire-and-porcelain swing top — was designed to hold carbonation in. Yeast fermenting two tablespoons of sugar in a sealed glass quart generates real pressure, and period bottles were thick for that reason. Ordinary modern bottles are not, and a burst one throws glass.
- A yeast cake is not a modern packetThe compressed fresh yeast cake of this period was a moist cake of variable size, strength and purity, and could carry wild organisms alongside the intended baking strain. There is no honest equivalence between a quarter of one of those and any current sachet, which is one more reason the timings here cannot be translated.
- What the drink actually wasMarketed as a tonic for consumptives and invalids, this cow's-milk koumiss was a mildly alcoholic, faintly effervescent sour milk sold by the bottle in drugstores. Anyone wanting the taste today should follow a current kefir recipe using purchased grains or a commercial culture, where the acidification is reliable and the fermentation is understood.
Koumiss proper is fermented mare's milk, made for centuries across the Kazakh, Kyrgyz and Mongol steppe, where mares were milked through the summer and the milk soured in leather bags with a resident population of lactic bacteria and yeasts — the result is tart, lightly fizzy and slightly alcoholic. European medicine took an interest in the second half of the nineteenth century, when Russian physicians established koumiss sanatoria on the steppe and reported improvements in tubercular patients; the enthusiasm travelled west, and since Western cities had no mares to milk, pharmacies and dairies sold a cow's-milk substitute built from milk, sugar and baker's yeast. That is exactly the formula given here.