Q TRANSACTIONS OF WAGNER 



84 



THE CHEMISTRY OF BREAD-MAKING 



volume of oxygen, which provides the vesiculation so difficult to accomplish 

 in this kind of bread. 



It may be mentioned here, although it is not a part of the bread-making 

 process, that the lightness of cakes and many other baked products is attained 

 in a purely mechanical way by the use of white of eggs, which, being beaten to 

 a stiff froth, entangles innumerable air-bubbles of some permanence, owing to 

 its viscosity. This froth, when mixed with a dough or batter, carries in the 

 necessary air to give lightness to the baked product. The rising up or puffing 

 out of the mass during baking, which is noted in all these instances of mechani- 

 cal leavening, is due to the expansion of the individual air-bubbles under the 

 influence of the heat of the oven. It must be said that the flavor of aerated 

 bread is markedly different from that made by either the chemical or biologic 

 method of leavening. The absence of any foreign salts and of those by-prod- 

 ucts of fermentation which produce subtle changes in the flavor, make it more 

 or less insipid when compared with bread made by either of the other methods 

 mentioned. 



2. Leavening the Dough by the Employment of Chemicals. — The chemical 

 methods of leavening are considerably older than the mechanical methods just 

 described. They are used because of their convenience rather than on account 

 of their economy. None of them is at present employed on the large scale in 

 baking bread for sale, being more frequently employed in the home for baking 

 biscuits than for making loaf bread, although they will serve for the latter 

 purpose also when used with knowledge developed by experience. They are 

 all subject to the same criticism, i. e., they usually leave in the baked articles 

 products of their reaction in the shape of mineral substances not normally 

 present in any food-stuff eaten by man in anything like the proportion in 

 which they occur in this kind of bread. 



The earliest chemical method of leavening which was developed in re- 

 sponse to a demand for a bread not made by fermentation (yeast-bread or 

 salt-rising bread) was used only on the large scale and consisted in the use of 

 hydrochloric acid and sodium bicarbonate in proportions so carefully regulated 

 that they exactly neutralized each other. The following reaction takes place: 



The carbon dioxid, being in gaseous form, produces the leavening of the dough. 



