Scientific Lectubes. 107 



this only at the expense' of bodies containing pliosplioric acid and 

 ammonia, like gluten. JSTow, bearing this in mind, yon will see how 

 it is possible to eliminate the bad effect of ferment. Instead of setting 

 aside the whole moistened flour to ferment, you will take a small 

 portion of a fermenting mass, the sour dough, full of germs of fer- 

 ment, and immerse it in material capable of yielding desirable pro- 

 ducts, in starcli, or gum, or sugar, as barley malt, or the starch of 

 boiled potatoes, in which there is a small amount of nitrogenous 

 and phosphatic ingredients, capable of feeding the yeast plant. The 

 dextrine, sucar and alcoholic ferments we want ; but we do not want 

 the acetic, or butyric or putrid ferments. We must pass through the 

 ammoniacal, which attends the saccharine fermentation. It ceases 

 at the commencement of the alcoholic. The acetic, butyric, putrid, 

 and one form of the lactic fermentations follow the alcoholic. Our 

 art then must be to avoid the lactic fermentation due to lov.' tem- 

 perature at the outset. Start with the dextrine or mucous fermenta- 

 tion, and go on steadily through the saccharine and its accompanying 

 phase of the ammoniacal, to the height of the alcoholic, when the 

 ammoniacal will be at an end, and stop before the acetic sets in. 

 Patience, and watchfulness, and science, within the bakery as v^'ell 

 as out of it, have accomplished this. The baker diluted the ferment 

 largely with dextrine, sugar or starcli, which would give especial 

 activity to the ferments resulting in alcohol and carbonic acid, and 

 sought to isolate the yeast plant suited to this object. 



Distillers' ajtd Bkewees' Yeast. 

 You have all heard of brewers' or distillers' yeast. Let me tell you 

 how they are produced. When a mass of ground rye, or corn, or 

 wheat, is brought with warm water and the addition of a small 

 quantity of yeast to a lively fermenation, the froth is skimmed oH' 

 and repeatedly washed in large volumes of cold water, from which there 

 settles out a line white powder. This is the yeast plant of the distilleries. 

 If the wheat, or rye, or corn, was sound, the yeast plant will be suited 

 to bread fermentation, but if it was sour, or in any way defective, 

 the yeast plant will carry the taint to the dough. The brewers' yeast 

 is made with more care ; crushed rye is mixed with malt meal and 

 fermented. The malt, as you know, is nuide from barley which has 

 been steeped in water, allowed to germinate to consume most of its 

 gluten or diastase, and convert its starch into dextrine and sugar, and 

 then roasted to arrest the germinaUon. Of course, the mixture of 



