FERMENTATION OF CARBOHYDRATES 189 



scale, is a cheap source of carbohydrate. Attempts have 

 been made to hydrolyze the cellulose of wood and other 

 materials, and this is being carried on on a commercial scale 

 in some of the southern states. Usually, however, potatoes 

 or cornstarch constitute the cheapest available carbo- 

 hydrate. This is hydrolyzed either by the use of malt or of 

 certain of the molds already described. It is then inoculated 

 with yeast and when fermentation is complete, the alcohol 

 distilled over. 



Alcoholic Fermentation in Bread Making. Many dif- 

 ferent leavening agents have been utilized in the prepara- 

 tion of bread. When wheat flour and water are mixed in 

 proper proportions, the gluten of the flour forms a sticky 

 or pasty mass, taking up most of the water. This is made 

 porous by the introduction of minute gas bubbles, usually 

 of carbon dioxide. This gas is, generally, on a commercial 

 scale, generated by the growth of yeasts. The yeast used in 

 bread making is of the same general type as that employed 

 in the manufacture of beer. It will be recalled that yeast 

 does not have the power to produce diastase, therefore fer- 

 mentation induced by the yeast cannot take place until 

 sugar is supplied. Flour contains small quantities of dias- 

 tase and when mixed with water there is sufficient formation 

 of sugar to allow of some growth of yeast. In commercial 

 bread manufacturing, however, there is frequently added 

 sugar, either maltose, dextrose, or sucrose, to increase the 

 rapidity of the yeast development. Frequently also various 

 chemicals are added to act as yeast stimulants. Certain 

 salts of ammonia and of phosphoric acid increase materially 

 the rapidity of yeast growth, and the production of alcohol 

 and carbon dioxide. When, as the result of the growth of 

 the yeast and proper kneading and mixing, the gas bubbles 

 of carbon dioxide have been sufficiently distributed through- 

 out the dough, it may be molded into form and baked. This 

 process drives off most of the alcohol, coagulates the protein 



