180 Dr, Colquhoun*s Essay [Sept, 



far than in former times, that the yeast becomes sour in the 

 bake-house before it is mixed with flour at all. The remedy for 

 this is, as may easily be supposed, of the same nature with that 

 which has just been described. To leave no doubt upon the 

 matter, it was subjected to the test of actual experiment, and 

 the results were as decidedly in favour of the good effects of 

 employing an alkali as could possibly have been anticipated. 

 Even after the yeast had been allowed to stand over for an entire 

 week in a warm situation, and had thereby acquired such a 

 concentrated acidity as entirely concealed its taste and smell, 

 the addition of an alkaU had the immediate effect of restoring 

 the natural yeasty flavour. It is only necessary to observe, that, 

 in such a case, the alkali should be added just so long as an 

 effervescence is thereby produced, and no longer. When sour 

 yeast had thus been corrected, it appeared in practice to possess 

 the fermentative principle in unimpaired activity, and to be 

 capable of being employed in a bakmg process with the same 

 success as yeast entirely recent and fresh. 



There seems then to be nothing more easy and nothing more 

 effectual than the application of this corrective of acidity. It is 

 only surprising that an inconvenience so annoying and disagree- 

 able, should have till now been tolerated by all classes of people, 

 when a simple remedy lay so close at-hand. 



The earlier portion of the process of bread-baking has now 

 been discussed ; we have briefly detailed the mechanical prac- 

 tice of the baker, and have offered a chemical explanation of the 

 accompanying phsenomena. And although the suggestion of a 

 remedy for the mischief of supervening acescence, has proved 

 a somewhat lengthy episode in the history of the loaf, yet it 

 seemed a matter of too much importance to be more slightly 

 passed over. It has now been pretty fully considered ; and 

 after the process of preparing bread for the oven has been thus 

 examined in detail, we proceed to examine what changes are 

 the results of baking in the oven. 



The true nature of these alterations remains as yet involved 

 in very considerable doubt and uncertainty. The first striking 

 effect observable, is, that however active may have been the state 

 of fermentation previously at work in the dough, before being 

 exposed to the fire, it is immediately checked and brought to a 

 period. But it has scarcely been yet determined what is the 

 precise action upon the constituents of the flour which follows, 

 and we shall now rather enumerate than discuss in detail the 

 various alterations which probably occur. 



It would appear to be the amylaceous ingredient which is the 

 subject of tile greatest subsequent change. It has already been 

 stated as pretty certain that there does also occur in the oven 

 the formation of a saccharine matter at the expense of any gela- 

 tinized starch which may have been formed during the early 



