172 Dr» Colquhoun's Essay [Sept. 



from the comparative weakness of the yeast, the spontaneous 

 dttCOtAposition was more tardy in commencing, less brisk in its 

 operation, and lasted longer than in the ordinary process ; hut 

 this, as is well known, is precisely what invariably takes place, 

 when saccharine matter is brought into a state of fermentation 

 by means of a ferment which is already either half-exhausted, 

 or whose fermentative power is naturally feeble. • "^-^ '^'' 



There seems to be but one objection to the adoptWn oTa 

 theory, which is supported by proofs so very strong as the^e 

 just mentioned, and that objection is more apparent than real. 

 After a loaf is baked, there is found still to exist in its compo- 

 sition almost as great a proportion of saccharine matter as occurs 

 in the original wheaten ilour, previously to fermentation. M. Vo- 

 gel found, that in a baked loaf there remained 3*60 of sugar, 

 which was only 1 or 1'5 per cent, less than had existed in the 

 flour before making it into dough.* And he very naturally 

 declares that he was not a little surprized by the fact, as he held 

 the same opinion on the subject of the fermentation in dough, 

 which has been supported in this Essay. 



But it must, in the first place, be recollected, that in every 

 loaf, as the process of fermentation has been invariably checked 

 at a very early period by the baker, that constituent, which was 

 the subject of the fermentation, can never be wholly, and will 

 often be but very partially, decomposed. And in addition to 

 this it seems almost certain that another and a sufficiently 

 interesting chemical change occurs during baking, and which, 

 if. the following account be correct, will easily reconcile the 

 large amount of sugar found to exist in bread after baking, with 

 the fact, that the saccharine principle was nevertheless the 

 subject of all the fermentation which had taken place. 



In the experiment of M. Vogel last referred -to, besides ascer- 

 taining the amount oi gluten to have been scarcely affected by 

 baking, and three-fourths of the starch to retain their properties 

 unaltered, it appeared that the remaining fourth had acquired 

 the properties of a gummy matter, analogous to torrified starch, 

 being readily soluble in cold water. Now the experiment to be 

 detailed seems to point strongly to the conclusion, that when 

 any part of a loaf of bread enters the oven in the state of gelati- 

 nous starch, the process of mere baking alters the relative con- 



♦ In 100 parts of loaf-bread, prepared with wheaten flour, distilled water and yeast, 

 irithout the admixture of any common salt, he found the following ingredients : 



Sugar . 3-60 



Torrified (or gummy) starch 1 8*0 



I Starch 5350 



Gluten, combined with a little starch 20*75 



Carbonic add — 



JVIuriate of lime ....,>.••.• '^'^ ••' *.t-ka* ... — 



Magnesia ". — 



(Joum. dc Phaxm. iii. 219.) 



