When the bread is thoroughly kneaded the sec ond time it is ready for the oven a fter rising. The best temperature for baking broad is from 450 to 550° F., so that the interior of the loaf will be at the boiling-point, or 212° F. During the process of baking the starch; of the flour is rendered solu ble by the heat, the fermenting growth is killed, that the starch is more easily acted upon by the digestive fluids.
Good fresh bread has a crisp crust which breaks with a snap, and an elastic crumb which springs back into shape after being pressed with the finger. Before bread is a day old, however, its texture has changed; its crust has become softer and tougher, while the inside seems dry and crumbly; the bread is 'growing stale,' as we say. This was formerly supposed to be due sim ply to the drying of the bread; but as the loss of water is found by experiment to he compara tively slight, some other explanation is necessary and various ones have been offered, of which the most interesting seems that given by Bontroux. Ire maintains that the apparent dryness is due to a shifting of the moisture from the crumb to the crust. When first taken from the oven the dry crust cools quickly, but the moist crumb retains its heat much longer. As gradually, how ever, its temperature falls to that of the su•round ing atmosphere, its moisture tends to pass out ward, leaving a comparatively dry crumb and moist crust. Common experience shows that if stale breath is put into the oven for a few minutes it regains something of its fresh eonsisteney crisp crest, and moist crumb. Such bread lacks the elasticity of the fresh loaf. and its interior ernmbles as easily as before it was reheated. This is supposed to be because the starch has undergone a chemical change, the nature of which is not yet clearly understood. Indeed, the whole question of staleness is one about which little has been absolutely proved.
The average percentage composition of a num ber of common kinds of bread is shown in the following table: It will be seen that wheat bread from low grade flour, wheat bread from bakers' flour, and rye-and-wheat bread contain the largest amount of protein; corn bread and wheat rolls, the most fat: and wheat rolls, wheat bread from high grade patent flour, and wheat bread from regular patent flour, the most carbohydrates. The
amount of fat would, of course, vary greatly with the amount of shortening added in making the bread, and the examination of a large number of analyses of the same kind of bread has shown that the amount of each of the several nutrients varies in the same sort of bread within rather wide limits. Judged by their composition, all breads are nutritious foods. and too great stress should not be laid on the variations in composi tion between the different kinds.
The chemical composition of the finished loaf differs somewhat from that of the original ma terial, as is shown by the following table, which compares flour and the breads made from it: The increase of water in the bread hardly needs explanation, since it is evidently due to the water added in making the dough. The use of butter or lard and salt probably accounts for the excess of fat and ash. The protein and carbohydrates lust doubtless went to nourish the yeast. Alost of the carbon dioxide into they were con verted passed out of the bread. According to Birnbaum the baked bread contains an average of 0.314 per cent. of alcohol, by no means all of that generated by the Yeast (about 1 per cent..
according to Snyder) ; part is evaporated and part is probably changed into acetic acid. The bacteria and other microscopic plants which ac companied the yeast doubtless took their share of the protein and carbohydrates, returning a part in the form of the characteristic acids and other bodies which they produce. Part of the starch in the crust has been changed into dextrin, end that in the crumb has become gelatinous or partly soluble. The gluten has taken definite shape: in other words, it has coagulated very much as the white of an egg does in boiling.