Ohervations on Fermentatiov . 223 



lile alkali formed in the operation neutralizes one part of 

 -the acetic acitl, as is proven bv the animoniacal ndour of 

 dough treated by potass. Bread itself always contains a little 

 of this acid, which heightens the flavour of it. 



3. The starch, the undcconipr)sed gluten, and the other 

 materials of the dough, are so intimately united by the bak- 

 ing, that it is no longer possible to separate them. We can 

 discover by the distillation of bread an anin)al matter, for 

 it forms ammoniacal acetate ; but a less quantity of this is 

 obtained from it than of farina, according to the observa- 

 tions of M. Vauquelin. 



4. The formation of carbonic acid gas is rendered evident 

 by the volume which the dough acquires, and by the nume- 

 rous cavities which are seen in it. This gas escaping 

 while the bread is baking, ddates the mass stilfmore, which 

 causes the air to lodge in those cavities ; an important cir- 

 cumstance, — whence results, say they, the ren)arkablc white- 

 ness of bread, full of little holes, so light, delicate and 

 sapid, in comparison with the bread destitute of them, 

 which is heavy, compact, and of a disagreeable taste. 



It is therefore more particularly {heferj?ient which has 

 the most active share in producing pannification. Added 

 to dough in small quantity, the operation is slow and in- 

 complete ; in too large proportion, the fermentation goes 

 on so rapidly that it becomes necessary to check it. In 

 this last case M. Chaptal proposes to knead some carbo- 

 nate of potass with the dough, which will neutralise the 

 excess of acetic acid. Our good housewives content them- 

 selves with uncovering the dough, dividing it, and expos- 

 ing it to the air, in order to diminish the temperature of 

 the fermenting mass ; and this management sometimes 

 succeeds. 



2. Of the Vinous Feimentat'wn. 



This operation can only take place when su<rar, water, 

 and a fernient are mixed together. Sugar is the matter of 

 fermentation ; the ferment Ts the agent of it ; the presence 

 of wafer is a necessary condition, as well as a certain de- 

 gree of temperature, 'it is because these three substances 

 exist m a slate of union in the saccharme juices, that these 

 are capai)le of the vinous fermentation. 



What are the chemical changes which substances sub- 

 jected to the vinous fermentation undergo? If one consi- 

 ders the composition of these substances, and that of the 

 products of the operation, it will be easy to conceive with 

 U. Thenard, that in it the ferment takes away from the 



sugar 



