The materials being at hand, and the proper benches, utensils, and oven being within reach, the baker takes a quantity of water and adds to it the yeast and salt; after which the flour is added, and the whole thoroughly and laboriously kneaded together till it. assumes a ropy consistence. It is then called the sponge, and is placed in a kneading trough iu a warm place, which is styled setting the sponge. In a short time, the yeast begins to act on the gluten, starch, and sugar of the flour, compelling the latter to pass into alcohol and carbonic acid gas in every part of the dough, which thereby becomes inflated with innumerable air cavities. When the fermentation has sufficiently advanced, the baker takes the sponge, adds more flour, water, and salt, and a second time subjects the whole to a thorough process of kneading, to prevent portions being so far fermented as to become sad, and again allows the mass to lie in a warm place for a few hours. The dough swells considerably from distension by gas, and is weighed out into lumps of the proper size, which are shaped into loaves, constituting the batch, or placed in tin pans, and are allowed to lie for a short time till they get further distended. The oven has previously been heated by flues, by heated air, or by wood being burned within it, to a temperature of at least 320° F., which is the lowest temperature at which B. can be baked, and ranging up to 572' F. ; and when it has been thoroughly cleaned out, the loaves are introduced and placed on the floor, and the oven shut up. The beat acts iu dissipating much of the water from the dough, in distending the air cavities more fully, and in partially boiling the starch and gluten of the dough, and developing some gum from the starch. Indeed, though the temperature of the oven is much higher, yet the loaves beyond the mere crust are bathed in an atmosphere of steam, and are never heated above 212', as has been proved by direct experiments with the thermome ter. One effect of the heat is to arrest any further fermentation (q.v.; see also YEAST). After several hours baking in the oven, the length of time being determined by the temperature, the loaves are withdrawn, and allowed to coo]. The brown appearance of the crust of loaves, and the pleasant taste of the crusts, are due to the action of the heat on the starch and the formation of dextrine (q.v.), a sort of gum. The number of quartern (4 lb.) loaves which a sack of flour weighing 280 lbs. yields, is 90. It will be apparent, therefore,that as 280 lbs. of flour yield 360 lbs. of B., that a good deal more water must be present in the latter than in the former; and indeed, ordinary good wheaten B. contains about 45 per cent of water. This water is retained even after the loaf is apparently dry, and even mealy, as the gum and gluten have a great affinity for water.
Improvements in the process of making B. are occasionally effected. Thus a form of yeast, called German harm or yeast (q.v.), has been introduced, which is more cleanly than ordinary yeast or leaven, but appears to be too rapid in its power of causing fer mentation to be manipulated easily in the making of ordinary loaves, though it does well for pan-loaves and fancy B. in genera]. Ovens heated by flues are being con structed, instead of the primitive method of heating them by wood, which smokes the whole oven. Instead of raising the dough by the action of yeast, which decomposes a part of the flour and causes the loss of about 2 per cent, bicarbonate of soda and hydrochloric acid are sometimes employed. The proportion by this process are 4 lbs. of
flour intimately mixed with 320 grains of bicarbonate of soda; to this is added a mixture of 300 grains of common salt in 35 ozs. of water and 61 fluid drams of hydrochloric acid, sp.gr. 1.16, and the whole is kneaded and placed in the oven. When the mix ture is made, the acid acts on the bicarbonate of soda, forming common salt, which is left in the dough, and carbonic acid is liberated at every point, and communicates a spongy texture to the dough. The disadvantage attendant on this mode of raising the dough is that it is apt to leave too much common salt in the bread. This is obviated by using water charged with carbonic acid, as described under AERATED BREAD. Sesqui carbonate of ammonia is employed to some extent in the preparation of rusks, ginger bread, and other light fancy B.; when heated, it entirely passes into gas, and thus yields a very spongy mass. Short-bread is prepared from flour which has been incorporated with butter. See UNFERMENTED BREAD.
The appearance which good wheaten B. ought to present, is that of a vesicular or spongy mass, from which layers can be readily detached; and this, known to bakers as piled B., is the best index of good wholesome and easily digested bread. When the layers cannot be detached, and the loaf cannot be crumbled down by the fingers into a coarse powder, or the fragments be thoroughly soaked and be readily diffused through water, but become a permanent tough mass of dough, the B. is imperfectly made.
Rye B. is very extensively used in northern European countries, where the soil being sandy is admirably adapted for the growth of that grain, It yields a flour-darker than wheat-flour. It is almost equal in nutritive value to wheaten bread. Barley and oats, which when used as B. are generally made into cakes or bannocks, possess also a composition not unlike wheat. Indian corn, which thrives luxuriantly on the Ameri can soil, and is largely used there for B., as also to a considerable extent in the old world, is little different from wheat in the proportion of its ingredients. Rice is occa sionally employed in making B., but it is not nearly so nutritious as wheat.
But although, with the exception of rice, the various kinds of grain do not differ in the amount of nutritious matter contained in the meal, yet there is a great difference as to the quality of yielding a light, spongy bread. In this respect, the flour of wheat excels all others. This quality seems to depend upon the mechanical structure of the gluten of wheat, which gives a glutinous, sticky consistency to the dough, rendering it impervious to the carbonic acid gas formed in it during the fermentation, so that the gas thus imprisoned swells it up. The meal of other grains forms a more granular and less tenacious dough, which allows the gas to escape with more or less ease as it is formed. It is thus impossible to make a light, spongy loaf of oatmeal, however finely it might be ground. In the case of whole-meal B. or brown B., the rough, hard particles of the bran interfere with the ordinary tenacious quality of wheaten-flour, and make the dough slightly porous, so that much of the gas escapes, and thus this kind of B. is never so much raised as B. of fine flour.