If we compare the baked loaf with the flour of which it is composed, we shall find that panary fermentation has pro duced a considerable change in the latter. The gluten and the starch, which (exclu sive of a trace of sugar) were the compo nents of the flour, have mutually acted upon and altered each other ; the tough ness and viscidity of the gluten is gone, and the starch no longer forms a gelati nous mixture with hot water ; a little sugar is generally formed, as well as al cohol; but the principal • cause of the change in the characters of the flour is the evolution of carbon and of oxygen in the form of carbonic acid, the production of which is independent of the presence of external oxygen (or of air). Small quantities of alum are also, it is said, invariably used with the view of whiten ing or bleaching the bread ; for it may be observed, that whatever may be the quality of flour which is used, home made bread is always of a comparatively dingy hue. According to Mr. Accurn, the requisite quantity of alum for this purpose depends upon the quality of the flour. The meidman, he says, makes different sorts of flour from the same kind of grain. The best flour is chiefly used for biscuits and pastry, and the in ferior kinds for bread. The smallest quantity of alum used is from three to four ounces to the sack of flour of 240 pounds.
Another article occasionally employed in bread-making is carbonate of ammo nia. As it is wholly dissipated by the heat of the oven, none remains in the baked loaf. It renders the bread light, and perhaps neutralizes any acid that may have been formed (exclusive of car bonic acid) ; but it is too dear to be much employed. To some kinds of biscuit it gives a peculiar shortness, and a few of the most celebrated manufacturers uselt largely. The French chemists have tie cased the bakers of employing sulphate of copper or blue vitriol, for the purpose of improving the color of the bread; but so dangerous and easily detected an addi tion can scarcely be supposed to be com mon. According to Mr. E. Davy, bread, especially that of indifferent flour, is materially improved by the addition of a little carbonate of magnesia, in the pro portion of twenty to thirty grains to the pound of flour ; it requires to be very intimately mixed with the dough. The most nefarious adulteration of bread con sists, however, in the addition of certain insipid and colorless earthy substances, with a view of increasing its weight ; such as pipe-clay, porcelain clay, chalk, and plaster of Paris. These, however, are probably very rarely resorted to ; though in one instance the writer of this article had occasion to examine a quantity of biscuits, which were adulterated with gypsum to the amount of 10 per cent. For the manufacture of domestic bread the following, perhaps, may not be un acceptable.
White Bread.—Take an earthen larger at the top than the bottom, and in it put a pint of milk-warm water, 11 lbs. of flour and 1 pint of good malt yeast ; mix these well together and set it away (in winter it should be m a warm place) until it rises and falls again, which will be in from three to five hours. It may be set at night if wanted in the morning. Then put two large table spoons full of salt into two quarts of wa ter, and mix it well with the above ris ing. Then put in nine pounds of flour, and work your dough well ; then set it by until it becomes light. Then make it out in loaves, of which it will make four. As seine flour is "dry," and other " run ny," the above quantity will be a guide. The person making bread will observe that runny, or new flour, will require one-fourth more salt than old or dry flour. The water also should be tem pered according to the weather. In spring and fall it should only be milk warm. In hot weather cold, and in win
ter warm.
Brown Bread.—Take one part of rye meal and two parts of Indian meal, mix it well, add a little salt, and thoroughly wet the whole with boiling milk. Stir it frequently, until cold, and add cold milk till it is thin enough to pour into pans. Bake it in a brick oven five or six hours.
Take six quarts of water, one teacup full of salt, one pint of lard or other clean grease, one pint of yeast, the whole to be quite warm ; then stir in meal enough to make a stiff batter, let it stand till it rises, then mix up and put in pans to bake. The quanties can of course be reduced proportionately as desired.
Unfermented Bread.—Five pounds of flour, 1 oz. sesqui carbonate soda, 1 dram sesqui carbonate of ammonia, 4 teaspoon fuls of common salt. Mix well together, and then add. a pints (50 oz.) cold wa ter, and 5 drama of hydrocloric acid. It requires 11 hours to bake.
The theory of panifiattion (bread-bak ing) is easy of comprehension. The flour owes this valuable quality to the gluten, which it contains in greater abundance than any other of the cerealia (kinds of corn). This substance does not consti tute, as had heretofore been imagined, the membranes of the tissue of the peris perm of the wheat ; but is inclosed in cells of that tissue under the epidermic coats, even to the centre of the grain. In this respect the gluten lies in a situa tion analogous to that of the starch, and of most of the immediate principles of vegetables. The other immediate prin ciples which play a part in panification are particularly the starch and the sugar ; and they all operate as follows : The diffusion of the flour through the water, hydrates the starch and dissolves the sugar, the albumen, and some other soluble matters. The kneading of the dough, by completing these reactions through a more ultimate union, favors al so the fermentation of the sugar, by bringing its particles into close contact with those of the leaven or yeast ; and the drawing out and malaxating the dough softens and stratifies it, introducing at the same time oxygen to aid the ferment ation. The dough, when distributed and formed into loaves, is kept some time in a gentle warmth, in the folds of the cloth, pans, &c., a circumstance propitious to the development of their volume by fer mentation. The dimensions of all the lumps of dough now gradually enlarge, from the disengagement, of carhonie acid in the decomposition of the sugar ; which gas is imprisoned by the glutinous paste. Were these phenomena to continue too long, the dough would become too vesic ular ; they must, therefore, be stopped at the proper point of sponginess, by plac ing the loaf lumps in the oven. Though this causes a sudden expansion of the enclosed gaseous globules, it puts an end to the fermentation, and to their growth, as also evaporates a portion of their wa ter.
The richness or nutritive powers of sound flour and also of bread are propor tional to the quantity of gluten they eon taM. It is of great importance to 'deter mine this point, for 'both of these objects arc of enormous value and consumption ; and it may be accomplished most easily and exactly by digesting in a water-bath, at a temperature of 167° F., 1000 grains of bread (or flour) with 1000 grains of bruised barley-malt, in 5,000 grains or in a little more than half a pint, of water. When this mixture ceases to take a blue color from iodine (that is, when all the starch is converted into so luble dextrine) the gluten left unchanged may be collected on a filter cloth, washed, dried at a heat of 212°, and weighed. The color, texture, and taste of the glu ten, ought also to be examined, in form ing a judgment of good flour, or bread (See FLouu.)