1826.] Dr. Colquhoun on the Art qJ Baking Bread. 263 



Article IV. jftTKiij^ 



A Chemical Essay on the Art of Baking Bread. ^^^ ^ 

 By Hugh Colquhoun, MD. ' ! ' 



{.Concluded from ^. 182.) 



II, Of certain Processes for introducing an Elastic Fluid into 

 ..the System of Dough, without having recourse to the Panary 

 ^'Fermentation. 



It is to the use of the sesqui-carboiiate of ammonia (the 

 common subcarbonate) that the baker, in this department of his 

 art, has most generally recourse ; and, perhaps, also, with the 

 surest success, as a means of duly gasifying his bread. When 

 this salt is employed, it is almost always in a proportion varying 

 between the quarter and the half of an ounce to the pound of 

 flour. It is dissolved in the water which is to be employed in 

 forming the dough, of which the proposed bread is to be made. 

 As soon as the due proportion of flour is mixed with the water 

 holding this salt in solution, and sufficiently kneaded into 

 dough, the composition is ready for the oven ; and whether 

 baked immediately, or after a moderate interval, to suit the con- 

 venience of the manufacturer, the same light spongy bread is 

 obtained. The heat of the oven operates directly in expanding 

 the carbonate of ammonia into an elastic vapour. In its endea- 

 vours to escape, the pent air opens up and detaches from each 

 other the compact particles of the dough ; the whole mass is 

 heaved up to a large increase of volume, and is maintained for 

 some time in a highly dilated bulk, notwithstanding the constant 

 escape of gas, which is forced out into the oven, by the continued 

 energy of the elastic fluid, until it is almost entirely expelled 

 from the bread. When the whole has nearly evaporated, the 

 bread subsides a little ; but it has already attained, through the 

 continued heat, a degree of stiffness and dryness through all 

 the parts of its texture, which prevents its shrinking back to 

 nearly its former dimensions. It remains not only increased in 

 bulk, but also hght and porous. 



But the structure of bread which has been thus prepared, and 

 indeed of all bread in which a sudden formation and develop- 

 ment of elastic fluid has been generated within the oven, differs 

 remarkably, when examined, from that of a loaf which has been 

 made after the preparatory fermentation by yeast. Bread which 

 has been raised with carbonate of ammonia, is certainly porous, 

 and the pores are numerous and excessively minute ; but that 

 which has been prepared from regularly fermented dough, is not 

 so properly porous as spongy and vesicular. And the former 

 kind of bread never presents any trace of that stratification of 

 layers of vesicles, which is held so high in the estimation of th^ 

 baker. 



