Yeast, as seen under the microscope, is in the form of cells which are circular in shape. It is a living germ, but it cannot move about from place to place, like an insect. Its power of movement is confined to growth only, like a blade of grass, or a plant of any kind. Yeast is therefore a plant of the lower orders. It requires air, but not light, to sustain life, it also requires warmth for favour- able growth, and it flourishes in a temperature of about 80° F. It has been proved that a single yeast germ, given favourable conditions, will multiply in twenty-four hours to considerably over sixteen and a half millions. Too great a warmth, or heat at 95° F., will make yeast ferment quickly, but this heat will also weaken its power. If heat is increased to 140° F. or more than that, the yeast is destroyed. On the other hand, if we keep yeast in a cold place it will retard growth. The lower the temperature the slower will yeast grow, until the temperature is lowered to 50° F., when the growth will stop, but it will recommence upon the temperature being raised. Actual freezing will not kill yeast, providing the yeast cells have not 33 been burst, and with careful and gradual warming, the yeast will recommence growing. Therefore, it is best to keep yeast cool when not required, and if you want it to keep for a long time it must be placed in the icehouse, should you be fortunate enough to have one. It sometimes happens when at sea that your yeast has turned sour. To avoid sour yeast it is advisable to make up no more than the quantity required for the amount of bread you are making up. Always retain a little of the old yeast to start the fermentation of the next lot, and continue doing so for the whole voyage through It may happen that the yeast which you have retained will turn sour. It will certainly do so in the course of a day or two if you keep it in a warm place. The cause of this sourness is principally lack of food (sugar) for the yeast, literally amounting to starvation. It then becomes weaker, and in its weak state falls an easy prey to other germs called “lactic” and “butyric.” Sometimes, in extreme cases, the acetic germ is also present. Lactic acid germs are the cause of sourness in milk. Butyric acid germs are the cause of the bad smell in very sour milk. Acetic acid germs are added to beer to make vinegar. All these germs will thrive in yeast, under certain conditions. If there is a sourness apparent in the yeast, strengthen it by making up a fresh quantity of yeast liquor (see recipes for yeast), add this to the yeast, and it will overcome the sourness, in fact, the acid germs will in their turn become prey to the yeast germ.

AI-modernized reading of the original text

Yeast, as seen under the microscope, is in the form of cells which are circular in shape. It is a living germ, but it cannot move about from place to place, like an insect. Its power of movement is confined to growth only, like a blade of grass, or a plant of any kind. Yeast is therefore a plant of the lower orders. It requires air, but not light, to sustain life, it also requires warmth for favourable growth, and it flourishes in a temperature of about 80° F. It has been proved that a single yeast germ, given favourable conditions, will multiply in twenty-four hours to considerably over sixteen and a half millions. Too great a warmth, or heat at 95° F., will make yeast ferment quickly, but this heat will also weaken its power. If heat is increased to 140° F. or more than that, the yeast is destroyed. On the other hand, if we keep yeast in a cold place it will retard growth. The lower the temperature the slower will yeast grow, until the temperature is lowered to 50° F., when the growth will stop, but it will recommence upon the temperature being raised. Actual freezing will not kill yeast, providing the yeast cells have not been burst, and with careful and gradual warming, the yeast will recommence growing. Therefore, it is best to keep yeast cool when not required, and if you want it to keep for a long time it must be placed in the icehouse, should you be fortunate enough to have one. It sometimes happens when at sea that your yeast has turned sour. To avoid sour yeast it is advisable to make up no more than the quantity required for the amount of bread you are making up. Always retain a little of the old yeast to start the fermentation of the next lot, and continue doing so for the whole voyage through It may happen that the yeast which you have retained will turn sour. It will certainly do so in the course of a day or two if you keep it in a warm place. The cause of this sourness is principally lack of food (sugar) for the yeast, literally amounting to starvation. It then becomes weaker, and in its weak state falls an easy prey to other germs called “lactic” and “butyric.” Sometimes, in extreme cases, the acetic germ is also present. Lactic acid germs are the cause of sourness in milk. Butyric acid germs are the cause of the bad smell in very sour milk. Acetic acid germs are added to beer to make vinegar. All these germs will thrive in yeast, under certain conditions. If there is a sourness apparent in the yeast, strengthen it by making up a fresh quantity of yeast liquor (see recipes for yeast), add this to the yeast, and it will overcome the sourness, in fact, the acid germs will in their turn become prey to the yeast germ.

Sea Cookery