BREAD and BAKING. There is a marked characteristio which separates bread into two kinds :— biscuit bread, which is made without fermentation, and is compact, heavy, and hard ; and loaf bread, which is fermented, and thereby rendered porous, light, and soft. The flour of barley, oats, and rye, is used as well as that of wheat for making bread ; but our brief details will apply more especially to wheaten bread, which is the most extensively used in England, and in which the properties of perfect bread are most distinctly exhibited.
In making biscuit bread [Iftscun], no chemical change is effected: the operation being the merely mechanical one of moisten ing particles of flour so as to cause them to adhere together, and to remain in one mass by the subsequent process of baking. The operation of making fermented bread is far less simple.
Wheat flour consists of starch and gluten, with a very small proportion of other sub stances : and the relative proportions of these constituents vary in different kinds of corn. A mode of comparing the qualities of flour in this respect has been already described. [ALEIIROMETER.] When flour is mixed with water, it forms the well-known paste called dough, which fer ments if left in a moderately warm place. During this fermentation, carbonic acid gas is evolved ; and this gas, in its natural tendency to escape into the air, is arrested in its pro gress through the dough by the adhesiveness of the gluten, and consequently forms the numerous cavities we seo in fermented bread. These are more numerous, and consequently the bread is lighter, when wheat flour is used than when the flour of oats or rye, which con tains less gluten, is employed. This natural process of fermentation however is slow and tedious, and is liable to impart a disagreeable flavour to the bread ; to remedy which, the custom of accelerating the fermentation by adding a small quantity of dough in a state of strong fermentation, called leaven, was intro duced. The substitution of yest (the frothy scum which rises on the surface of beer during 'its fermentation,) for this leaven is a further improvement.
In the ordinary mode of making bread the water is used at a temperature of from 90° to 100°, a little salt and yest is mixed with it, and then a quantity of flour. The substance thus produced is covered up and set aside in a warm situation : this part of the process being called setting the sponge. Within an hour the progress of fermentation is mani fested by the swelling and heaving of the sponge ; and this process is allowed to proceed, with the occasional dropping or sinking of the dough when the confined gas becomes so powerful as to force a way for escape, until a period dictated by experience as that beyond which further fermentation would be hazard. ous. The baker then adds the remaining flour, water, and salt, and incorporates all the materials thoroughly together by long and laborious kneading. When this has been con tinned until the dough will receive a smart pressure of the hand without adhering to it, it is again left to ferment for a few hours, and afterwards kneaded more gently, in order so to distribute the gas engendered within it as to make the bread equally light and porous throughout. It is then formed into loaves, which being set aside for an hour or two, ex pand to about double•their original volume : and these loaves are finally baked in the oven, by which process they enlarge still more in bulk, not by the continuance of fermentation, but by the expansion of the gas already formed, through the effect of heat. The result is a loaf composed of an infinite number of cel lules filled with carbonic acid gas, and lined with a glutinous membrane.
When flour is converted into bread, it is found on leaving the oven to have increased from 28 to 34 per cent. in weight ; but bread which has gained 281bs. will lose about 4lbs. within thirty-six hours after leaving the oven. The season of growth, the age of the flour, and other circumstances, affect the quantity of bread obtainable from a given weight of flour ; but generally speaking the better the flour is, and the older, within certain limits, the greater will be the quantity of bread.