CHAPTER VIIL* 

 THE MANUFACTURE OF OTHER FERMENTED PRODUCTS. 



PREPARATION AND CONSERVATION OF FOOD MATERIAL. 



COMPRESSED YEAST. Yeast in the form of a thick paste is produced 

 in large quantities for the use of bakers. It should be white, vigorous 

 and rich in nitrogen. 



In the Vienna method, a saccharine solution is made in a manner 

 similar to that used in distilling, by saccharification with malt and acidi- 

 fication by lactic bacteria. Many grains, principally barley, malt, rye 

 and corn, are used. A mixture of the three gives a solution which has the 

 required concentration and the proper degree of viscosity to facilitate the 

 separation of the yeast. 



The yeast is obtained by skimming off the surface and, after separating 

 from impurities by screening, washing and pressing it. 



In the method by aeration, a clear, saccharine, acid liquid is prepared 

 and fermentation conducted with thorough aeration by means of com- 

 pressed air. The yield of yeast is about double by this method and the 

 yield of alcohol considerably less. 



As the fermentation takes place in a clear solution the yeast is obtained 

 by settling and decantation in a sufficiently pure condition. It is then 

 washed and pressed as in the other method. 



BREAD. The raising of the dough to which the lightness and porosity 

 of bread are due is caused by the production of carbon dioxide by yeast 

 fermentation. The yeasts are always accompanied by bacteria and the 

 character of the bread is determined in great part by the extent of bacterial 

 fermentation. 



If we make a dough of flour and water and allow it to stand in a warm 

 place it will rise slowly. Yeasts and bacteria, occurring naturally in 

 the flour and water, are the causes. Bread is sometimes made in this 

 way (Graham bread, salt-rising bread). The rising is more or less 



* Prepared by F. T. Bioletti. 



460 



