I7?t Dr. Colquhvuiis Essat/ [Sept. 



fermentation being now satisfactorily gained in the eBtabiish- 

 ment of the precise subject of its exclusive action, the next 

 important matter is to ascertain whether this fermentation be 

 truly sui generis, or to which of the fermentatiofis, t)h« yiaotis^ 

 the acetous, or the putrefactive, does it belong. ^' 'ii h« '^ 



That which first commences within the baker s dough, pro- 

 vided it be of ordinarily good quality, is certainly the common 

 vinous or alcoholic fermentation. This is plain from the fact 

 already stated, that the appearances of the vinous fermentation 

 of aimple sugar, resolving itself into alcohol and carbonic acid, 

 are precisely the same with those which, in the process of 

 fermentation, as it is usually conducted in the bake-house, 

 occur in dough. But a remarkable change in the character of 

 the panary fermentation is always found to occur if it be allowed 

 to proceed far enough ; and as this change, whenever it super- 

 veaea, has the effect of injuring the quality of the bread, and is 

 accordingly the dread of the baker, it is material to inquire into 

 the nature of the secondary alteration, which, at a certain stage 

 of advancement, will always take place. 



The mode in which the new substance shows itself, when 

 generated in this subsequent fermentation of the dough, is per- 

 fectly well-known to the baker. Fermentation may, with good 

 materials, and in ordinary circumstances, be easily carried on by 

 him to the extent requisite to produce a light and well-raised 

 loaf, which yet shall be sweet and pleasant to the taste. But he 

 is well aware that if he do not check the fermentation of his 

 dough in due time, it becomes invariably sour, and the sourness 

 increases in proportion as the fermentation has been allowed to 

 pass its proper limit. It is only from practice, however, which 

 teaches him to judge by appearances, that he acquires the art of 

 distinguishing the moment when his interference becomes 

 necessary to stop the process of fermentation, and the conse- 

 quent generation of acidity. 



The source of the formation of this acid has been ascribed at 

 different times, and by different chemists, to each of all the 

 several ingredients of flour; to its gluten, its starch, and its 

 saccharine principle. There appears now, however, scarcely 

 any room left for doubting, that the greater portion of it, at 

 least, is invariably the consequence of a second Jet-mentation ; and 

 that it is produced by the very famihar process of the acetifica- 

 tion of the alcohol which had been developed in the original 

 fermentation of the saccharine principle. That the starch, or 

 even the gluten, should ever contribute to its formation appears 

 extremely unlikely, at least in the ordinary routine of bread- 

 making ; although there are reasons for suspecting, that in those 

 cas£s in which the sponge or dough has been too long kept, or 

 in which the fermentative process has been in other respects 

 unskilfully conducted, a portion of the albuminous and mucila- 



