I64r Dr. Colquhouii's Essay [Sept. 



and" operation of the ojaseous principle thus artificially introduced 

 into bread for the purpose of rendering it light and elastic, and 

 this shall form the subject of the present Essay. 



In conducting this inquiry, we shall commence, for the sake 

 of perspicuity, by stating shortly the mechanical history of the 

 most ordinary process of baking. We shall next cousicler in a 

 chemical point of view the use and object of each part of the 

 process, in so far as it contributes towards the duly gasifying* 

 of bread, so as to render it that light and spongy food which 

 makes it at once both pleasant and wholesome. And in dis- 

 cussing this matter, we shall divide the Essay into two parts. 

 The first of these we shall devote exclusively to the process of 

 panary fermentation, by far the most interesting and extensively 

 useful of all the methods employed by the baker in order to 

 impregnate his dough with the elastic fluid. In the second, we 

 shall consider more cursorily a few of the principal among the 

 other chemical processes resorted to by the baker, with a view 

 to gasify his bread. Among these, we shall find that there is 

 one, used in the manufacture of gingerbread, sufficiently import- 

 ant in itself, and sufficiently curious and anomalous with respect 

 to its rationale, to require a much more careful and minute 

 examination than any of the others ; and with this we shall 

 conclude the Essay. 



Mechanical Details of the most copimon Process in the Art of 

 Baking Bread, 



The spontaneous decomposition of a piece of wheat dough, 

 always generates within the mass a quantity of carbonic acid 

 gas; and it is the formation of this gas which is the baker's 

 object in exciting fermentation. The modes employed by him 

 may therefore be considered comparatively good, in proportion 

 as they more perfectly and rapidly produce the internal gas. 

 Perhaps the most simple process for effecting this, is to place a 

 portion of common dough apart, in a warm situation, where, if 

 allowed to remain a sufficient length of time, it will pass sponta- 

 neously into a state of decomposition, which will generate car- 

 bonic acid gas within it, and give the bread that is baked from 

 it both lightness and vesicularity. This system, however, is 

 attended not only with considerable delay, but with the further 

 disadvantage, that such dough is never entirely free from 

 acescence or putrescence, either of which is always injurious to 

 the flavour of the bread, and may even, if existing in excess, 

 prove detrimental to its wholesomeness. But the process of 

 decomposition will be found to be greatly accelerated in any 

 recent mass of fresh dough, by the addition of a small portion of 

 old dough already in a state of strong fermentation. When this 



• For shortness' sake the t^rm gasifying is used to express the common infusion of a 

 or elastic fluid into the system of dough. 



