1826,] on the Art of Baking Bread, 167 



which, expanded by heat throughout all the parts of the entire 

 system of each loaf, swells out its whole volume, and gives it the 

 piled and vesicular structure. When it is recollected, that the 

 gas thus generally expanded has been previously distributed by 

 the baker throughout the bread, and that the whole dough has 

 been by kneading formed of a tough consistence, the result 

 becomes apparent that the well-baked loaf is composed of 

 an infinite number of cellules, each of which is filled with 

 carbonic acid gas, and seems lined with or composed of a gluti- 

 nous membrane ; and it is this which communicates the light, 

 elastic, porous texture to the bread. 



Such is the mechanical history of the most ordinary and 

 common process followed out by the baker in making a modern 

 loaf. There is nothing of peculiar attraction about it, but the 

 want of this is amply compensated by the interest which a 

 chemical examination into the nature and principle of the 

 fermentative process, as here exhibited, excites. This is an 

 investigation which has at different times attracted a considera- 

 ble share of the attention of several chemists. Their opinions, 

 as will soon be found, have been extremely various in regard to 

 almost all its details. But among the latest writers on the 

 subject, there may be remarked a greater coincidence of views, a 

 sounder and more consistent solution of the different phaenomena 

 which present themselves, and a gradual tendency towards 

 unanimity of sentiment on the most important topics. How far 

 the experiments about to be detailed may be calculated to 

 further so desirable a consummation, as the exposition of a 

 chemical theory explaining satisfactorily all the details of the 

 fermentative process in the art of bread-baking, cannot be here 

 decided. At all events there has been the greatest anxiety, on 

 the one hand, to avoid every thing uncandid in the statement of 

 any opinion that is combated, of which it has been necessary to 

 mention several; and on the other, to advance nothing strained, 

 in support of any view that may be defended in the following 

 pages. If there be any erroneous statements, they have not 

 been wilfully made, and will be corrected as soon as pointed 

 out. Witn this explanation we proceed to our chemical 

 inquiry. 



I. Of the Nature of the Fanary Fermentation, 



There are three principal constituents of all wheaten flour ; 

 starch, which exists in the largest proportion ; gluten ; and a 

 saccharine principle. About thirty years ago, when the ideas 

 of chemists regarding the elementary constitution of organized 

 substances were less precise than at present, the difficulty of 

 assigning to fermentation in dough a place under any of the 

 three usual classes of the vinous, acetous, and putrefactive 

 fermentation, led to the conception that it was a species of 



