74 Dr Colquhoun on the Art oj baking Bread. 



principle, to ascertain which is essentially concerned in that 

 process. The researches of Dr C. have led him to the opi- 

 nion, that the fermentation in dough, so far as it is useful to 

 the baker, is solely owing to the resolution of the saccharine 

 principle of the flour into carbonic acid and alcohol, in conse- 

 quence of its being brought into a situation predisposing it to 

 pass into the vinous fermentation. 



If the saccharine fermentation be suffered to exhaust itself 

 in any dough, a new fermentation of a different kind (the 

 acetous) will succeed it ; but it is the latter which io injurious 

 to the bread, while the former is the source of all the benefits 

 which the best fermentation can confer. 



Dr Colquhoun proves, in the first instance, that the starch 

 and gluten are not concerned in the fermentation. Starch, he 

 observes, " evinces no tendency to undergo any decomposition 

 by mere exposure for a few hours to the moderate temperature 

 used in the preparation of dough ; and even moist gluten, in 

 the short period necessary to commence and complete the fer- 

 mentation of dough, would sustain no change in its appearance 

 or chemical properties, though exposed either per se, or mixed 

 with yeast, to the temperature just mentioned ; yet the fer- 

 mentative process in dough is strong under these very circum- 

 stances. Besides, it is certain, that if spontaneous decomposi- 

 tion, either of the starch or the gluten, always of compara- 

 tively tardy excitement, were once commenced and left un- 

 checked in circumstances so favourable to decomposition as 

 in the baking process, with respect both to moisture and tem- 

 perature, it would of necessity continue with regular and un- 

 abated energy, so long as a particle of either substance remained 

 unaltered. But in dough, though the fermentation commences 

 soon after the mixture of yeast and hot water with the flour, 

 and goes on actively and in full vigour for a given period, vary- 

 ing from twenty-four to forty-eight hours, it suddenly stops short, 

 while yet it is quite obvious, that much of the starch and of 

 the gluten remains untouched. In fine, it may be mentioned, 

 as conclusive of this question, that when fermentation has 

 thus ceased in dough, neither the addition of fresh yeast, nor 

 of fresh starch, nor of fresh gluten, nor of all the three com- 

 bined, has the smallest effect in renewing the process of fer- 



