Mrs. Lincoln's Boston cook book

Now, bread-dough contains gluten, sugar, and starch ; and if the dough be kept warm for a certain time, lactic fermentation will be developed spontaneously^ and the bread made from such dough will be sour and heavy. Alcoholic fermentation can also be spontaneously produced in dough, b}^ making first a batter (as the semi-fluid state is more favorable to rapid chemical change), and subjecting it to a temperature of 110° for five or six hours ; then, adding more flour, allowing it to rise again, and then baking it. Bread made in this way is called salt or milkrising's bread. But it does not keep well, and is not generally liked. It is not always convenient to wait for dough to be raised in this manner, so we hasten the process by the addition of some active ferment. Leaven, or a piece of old dough, left to sour, and then mixed with the new dough was formerly used ; this produced lactic as well as alcoholic fermentation, and though the bread was light and spongy in texture, it had an unpleasant sour taste. But since the chemistry of yeast fermentation has been understood, yeast has come to be considered the best ferment for producing alcoholic fermentation in bread rapidly, and with no objectionable result. The Boston Cook Book. Teast, what is it? — Yeast is a plant or germ of the fungus tribe. Under the microscope it is found to consist of numberless minute rounded or oval bodies which are true vegetable cells. Yeast is therefore one of the simplest or sap. They grow or expand from the minutest microscopic points, and seem to bud off from each other and multiply into many millions to the cubic inch. These cells are easily propagated in any medium where they find congenial food, particularly in the juice of grapes. If grape-juice be filtered and left to stand in a warm place two or three hours, it becomes first cloudy, then thick, and gives off bubbles of gas, showing there has been some change in its composition. In a short time a grayishyellow froth, or layer of yeast cells, collects on the surface. " Whether the germs or spores of the yeast plant exist already in the juices of the living grape, or whether they are always floating in the air, and cling to the exterior of the fruit, and only become mixed with the juice in the winepress, is not known ; " neither is it known just how they decompose the sugar of the grape. But it is enough for our purpose to know that they grow in the juice and expand there, and that an active ferment may be dissolved out of these yeast cells, sufficient to cause alcoholic fermentation. The natural development of yeast through the agency of plants is too slow and inconvenient a process to rely upon ; therefore we manufacture it from various substances rich in starch and sugar. Brewer's yeast is made from malt, or sprouting grain, usually barley ; home-made j^east, from flour and potatoes. Yeast Bread the Result of Chemical Changes. — Bread properly made with yeast undergoes certain chemical changes which render it lighter, more porous, more pleas- FiG. 4. Yeast Plant. and smallest of vegetable organisms. Each little cell consists of an enveloping skin or membrane, containing a liquid The Boston Cook Book,