188 EFFECTS OF BAD YEAST. 



customer, or rather to deceive him into the belief that 

 he is buying better bread than is really the case. 

 The increased lightness which it causes is, however, 

 really an improvement. 



458. Some bakers have even added sulphate of 

 copper to the dough. This salt produces, in very 

 minute quantity, the same efi'ects on bread as alum 

 does. Being a highly poisonous salt, its use is most 

 objectionable ; fortunately, it is an adulteration very 

 easily detected. 



459. Carbonate of ammonia, which is sometimes 

 mixed with slightly damaged flour, is a harmless ad- 

 dition. It does not improve the color of the bread, 

 but renders it lighter, and removes any sour flavor 

 which the bread might otherwise acquire, either from 

 the inferior quality of the flour, or the nature of the 

 ferment employed (462). 



460. When bread is made with leaven, it always 

 has a distinctly sour taste ; this is partly caused by 

 the leaven itself, and partly by an acid fermenta- 

 tion which it induces in the flour or dough. It 

 sometimes happens also that bread which is made 

 with barm or yeast has a similar sour taste ; this is 

 usually caused by want of skill or care in the prepa- 

 ration. It is occasionally caused by the use of sour 

 yeast, when the latter has been kept too long or is 

 spoilt, and then of course the bread will have a sour 

 taste, the same as if it were made with leaven. 



461. In places where a fresh supply of new yeast 

 cannot always be had, sour yeast must sometimes be 



