Fermentation.
The process of fermentation, which has for its object either the manufacture of bread, or of an alcoholic product in a more or less concentrated form, is very similar in action during its earlier stages. It commences with the growth and multiplication of the fermenting germs contained in the minute organisms floating in the air, the inorganic constituents of the water, and the protoplasm (essence of life) of the yeast; and all the changes brought about are accompanied by heat. Fermentation is caused by the decomposition of the starch and gluten of a solution of either potatoes, flour, or malted barley, which decomposition is accompanied by an evolution of gas. There is also a peculiar vibration given to the various bodies in contact, which agitates the whole. This agitation is increased by the bursting of the starch-cells and the formation therefrom of maltose, and also by the changing of the maltose sugar into carbonic acid gas. Substances in a state of decomposition are capable of bringing about a change in the chemical composition of bodies with which they are in contact. Most of the vegetable substances used in fermentation have a constituent part—sugar, starch, or some other substance—which is easily converted into a fermentable sugar by the action of yeast, or of diluted mineral acids, or by a constituent of malted barley, called diastase. The sugar produced by these means is resolved into carbonic acid gas and alcohol by vinous fermentation. It will be seen, therefore, that fermentation is started by the saccharine element in the ferment, which is termed maltose; the process is then kept up by the gluten, which, becoming decomposed, aids the sugar and starch in the work of providing food for the yeast as soon as the latter is brought in contact with it. The fermentation then takes place very rapidly, and carbonic acid gas is generated and given off in proportion to the amount of the products contained in the ferment, or sponge, and also to the strength and freshness of the yeast: especially is this so with gluten, which is the great agent of fermentation, when in a state of decomposition and when in contact with yeast.
Process of Bread-Making.
It will be useful to give here some remarks by the great scientist, Liebig, on the best process of making bread:—
“Many chemists are of opinion that flour by the fermentation in the dough loses somewhat of its nutritious constituents, from a decomposition of the gluten; and it has been proposed to render the dough porous without fermentation by means of substances which when brought into contact yield carbonic acid. But on a closer investigation of the process this view appears to have little foundation.
“When flour is made into dough with water, and allowed to stand at a gentle warmth, a change takes place in the gluten of the dough, similar to that which occurs after the steeping of barley in the commencement of germination in the seeds in the preparation of malt; and in consequence of this change the starch (the greater part of it in malting; in dough only a small percentage) is converted into sugar, a small portion of the gluten passes into the soluble state, in which it acquires the properties of albumen, but by this change it loses nothing whatever of its digestibility or of its nutritive value.
“We cannot bring flour and water together without the formation of sugar from the starch, and it is this sugar and not the gluten of which a part enters into fermentation, and is resolved into alcohol and carbonic acid.
“We know that malt is not inferior in nutritive power to barley from which it is derived, although the gluten contained in it has undergone a much more profound alteration than that of flour in the dough, and experience has taught us that in distilleries where spirits are made from potatoes, the plastic constituents of the potatoes, and of the malt which is added after having gone through the entire course of the processes of the formation and the fermentation of the sugar, have lost little or nothing of their nutritive value. It is certain, therefore, that in the making of bread there is no loss of gluten.
“Only a small part of the starch of the flour is consumed in the production of sugar, and the fermentative process is not only the simplest and best but also the cheapest of all the methods which have been recommended for rendering bread porous. Besides, chemical preparations ought never, as a rule, to be recommended by chemists, for culinary purposes, since they hardly ever are found pure in ordinary commerce. For example, the commercial crude muriatic acid which it is recommended to add to the dough along with bicarbonate of soda, is always most impure, and often contains arsenic, so that the chemist never uses it without a tedious process of purification for his purposes, which are of far less importance than making bread light and porous.