76 Dr Colquhoun on the Art of baking Bread. 



two ways. In the first place, the baker never allows the whole 

 sugar to be destroyed, lest the acetous fermentation should 

 set in. As. soon as the fermentation has proceeded a certain 

 length, and before all the sugar is decomposed, its progress is 

 arrested by the heat of the oven. In the second place, Dr C. 

 is of opinion, that some of the starch is converted into sugar 

 during the baking. Pure dry starch does not indeed undergo 

 this change ; but if any part of a loaf enters the oven in the 

 state of gelatinous starch, then saccharine matter is actually 

 formed at the expence of the starch. This was proved by an 

 experiment, in which wheat-starch was gelatinized by hot 

 water, and mixed with dough. The bread so formed had an 

 unusually sweet taste. Dr C. thinks it probable, that, in the 

 common process of making dough, a portion of starch is con- 

 verted into the gelatinous state. 



Having established that the fermentation of bread is merely 

 an instance of the vinous fermentation,, during which saccha- 

 rine matter is resolved into alcohol and carbonic acid, Dr C. 

 of course infers, that the production of an acid, when the pro- 

 cess is allowed to continue too long, is owing to the acetous 

 supervening on the vinous fermentation. He also suggests, as 

 a probable circumstance, that a little lactic acid is produced as 

 well as vinegar. 



Dr C. has also discovered an easy and certain method of de- 

 stroying the acescency of dough, when the fermentation has 

 accidentally proceeded too far, without giving any unpleasant 

 flavour or noxious quality to the bread. A quantity of ordi- 

 nary loaf-dough, when just fit for the oven, was put aside in 

 a warm situation. The acetous fermentation was soon esta- 

 blished, " and at the expiration of twenty-four hours, upon 

 opening up the dough, which was still in a state of strong fer- 

 mentation, a very acid odour was plainly perceptible. The 

 taste was also distinctly, though weakly, acid. After taking 

 two pieces, weighing five ounces each, from the general mass, 

 it was once more set aside. Into one of the portions thus 

 chosen were kneaded ten grains of the common carbonate of 

 magnesia, and then both were, after the usual manner, baked 

 in the oven. The difference between the two loaves, when 

 baked, was most striking. The bread which had been made 



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