Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/271

Rh preponderates, the result is the formation of the products desired by the baker carbonic acid and alcohol; but when the influence of cerealin prevails, lactic fermentation ensues, and dextrin, sugar, and acid substances are formed, which it is the object of the baker to avoid. Several methods of avoiding this deteriorating influence of cerealin, and at the same time securing the use of the maximum of flour, have been put in operation by M. Mege Mouries. The process now in use at the Boulangerie Centrale de 1 Assistance Publique (the Scipion) in Paris, for the preparation of the flour and baking white bread with the whole of the mill products excepting the bran, he thus describes: &quot;The corn is moistened with from 2 to 5 per cent, of water satu rated with sea-salt, and at the end of some hours the ex terior coverings only become moist and tender. The grain is then thrown between near 7 closed millstones, and 70 per cent, of flour is obtained without cerealin, plus 10 to 14 per cent, of meal. This is bruised between light stones, and separated by winnowing from the greater part of the husk remnants. To prepare the bread, all the leaven is made with flour at 70 per cent., and the meal is added to the soft dough last of all; as, in spite of the small amount of cerealin which it still contains, it will not produce brown bread, because at that time the length of incubation is not sufficient to change it into a leaven. Thus white bread is produced containing all the farinaceous part of the wheat.&quot; It not unfrequently happens that flour of good colour, and imexceptionable chemical composition, fails to yield a dough which will rise by fermentation, and the loaf from which is sweet, solid, sodden, and adhesive. Wheat that has been badly harvested, or which in any way has been allowed to sprout, has part of the gluten changed into the form of diastase, which, like cerealin, changes starch into dextrin and sugar. The gluten of flour which has been dried at a too high temperature, and of flour which has been kept in a damp situation, is modified and acts in the same manner. If dough is made with an infusion of malt, it yields a result exactly the same as that above described. It is to guard the starch of inferior flour against this deteriorative influence that a proportion of alum is used by many bakers of second-class bread. Alum has the power of preserving starch to a large extent from the metamorphic action of altered gluten, diastase, or cerealin, and of producing from an inferior flour a loaf of good texture and colour. The use of alum is regarded as an adulteration, and heavy penalties have been imposed on its detection; but its estimation in bread is a process of the greatest difficulty, and authorities are by no means agreed as to its deleterious influence. Other mineral salts have a similar protective power on the starch of inferior wheat, and lime-water has been successfully employed in place of alum. To this also it is objected by some that the addition of lime renders the valuable phosphatic salts of flour in soluble by transforming them into phosphate of lime.

Aerated Bread.—When carbonic acid, instead of being generated by fermentation within dough, is separately pre pared and incorporated with flour and water, aerated bread is produced. The system by which this is effected was invented by the late Dr Dauglish, and aerated bread has been manufactured under his patent since March 1859. The system is now in operation in all the principal towns in the United Kingdom, and it appears to be steadily gaining in public favour. FIG. 3. Dauglish Apparatus double set. The Dauglish apparatus (see fig. 3) consists of the follow ing parts : 1st, a generator A, in which carbonic acid is evolved from chalk by sulphuric or hydrochloric acid; 2d, a gas-holder, in which the carbonic acid is stored for use after being purified in passing through water; 3d, an air- pump, for pumping carbonic acid from the gas-holder, and forcing it into the water vessel and mixer; 4th, another Aerated air-pump, for withdrawing atmospheric air from the mixer tread. before the aerated water is admitted; 5th, a water vessel B, a strong cylinder of copper capable of withstanding a pressure of 100 Db on the square inch, and of sufficient size to contain water for a full charge of the mixer; attached to this water vessel there are a gauge-glass C, and a pressure gauge D, for indicating the pressure of gas as it is pumped in; 6th, the mixer E, a globular vessel of cast-iron, capable of bearing high pressure, through the centre of which an axle runs, fitted with iron kneading- arms extending to the circumference of the vessel. The pumps and the revolving arms within the mixer are worked by steam power. In order to make a sack of flour into dough, a lid at the top of the mixer is opened, and the flour passed down into it through a spout from the floor above. The lid of the mixer is then fitted tightly on, and the air within it exhausted by the pump. The requisite quantity of water, about 17 gallons, is drawn into the water vessel, and carbonic acid is forced into it, till the pressure amounts to from 15 to 25 5&amp;gt; per square inch. The aerated water is then passed into the mixer, and the mix ing arms are set in motion, by which, in about seven minutes, the flour and water are incorporated into a perfectly uniform paste. At the lower end of the mixer a cavity F is arranged, gauged to hold sufficient dough for a 2-Ib loaf, and by a turn of a lever that quantity is dropped into a pan ready for at once depositing in the oven. The whole of these operations can be per formed in less than half an hour. When 4-lb loaves are to be baked the lever has simply to be twice turned, At another part of the lower end of the mixer is placed a pipe G, with a stop-cock, by which dough intended to be fired as Paris bread, on the sole of the oven, is drawn off and weighed before being placed in the oven. The pressure of gas within the mixer is sufficient to force out the whole of the dough, which, immediately on being liberated, swells up by expansion of the gas confined within the tenacious mass. Currant loaves and various kinds of fancy bread are made by the aerated process by placing the necessary ingredients in the mixer along with the flour. The advantages claimed for Dr Dauglish s process are:—

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