V2 



Katio of Alcohol to Yeast in P'ermentation. By Katherine E. Golden. 



Fermentation is, essentially, the breaking \i]} of chemical compounds into 

 simpler and more stable compounds. Some form of fermentation goes on in all 

 living cells, the nature of the fermentation and the resulting products depending 

 on the organism and the body fermented. The results may he simple, as, for ex- 

 araj)le, where a single organism is used, or complex where a number of organisms 

 are working together. Where a single organism is used, the predominating re- 

 sulting product gives the fermentation its name. 



In the alcoholic fermentation, besides the akohol are formed COg, succinic 

 acid, glycerine and a number of by-products, the nature and quantity of which 

 depend on the orgenism, and the conditions under which it is grown. Beers and 

 wines depend mainly on these by-products for their aroma and special character, 

 so that experimenters, using the same kind of grape, have obtained many different 

 wines; the same way for beers, using the same wort, but varying the yeast, dif- 

 ferent beers are obtained. Even from apple must good wines have been pi*o- 

 duced, by the use of certain yeast cultures. Again, mixing certain yeasts in the 

 brewing, characteristics are obtained which are impossible with a single form. 

 Large breweries noM' have comi)etent bacteriologists, who seem to the uninitiated, 

 to be able to manipulate their yeasts, molds and bacteria much as a juggler does 

 his implements. 



Yeast is the organism most commonly used to induce the alcoholic fermenta- 

 tion, though it can be induced also by certain bacteria and molds. The yeast 

 which is used in brewing is S. cerevisise, there being two well marked varieties, 

 the cerevisia', which produces top fermentation, and that which produces bottom 

 fermentation. Top yeast works at a comparatively high temperature, the action 

 is rapid, and the yeast rises to the surface of the liquid; this is used in the 

 brewing of ale and porter. Bottom yeast works at a low temperature, the action 

 is slow, and the yeast is at the bottom of the liquid; the bottom yeast is used in 

 the brewing of lager beer. 



Wort, which is the basis of beer, is made in the following manner: First 

 there is the malting of the grain, which consists of the germination; then the 

 stoppage of the germination by heat. The first stages are for the purpose of 

 changing the chemical constitution of the grain ; diastase is developed from the 

 albuminoid matter; the diastase then acts on the starch, changing it to maltose 

 and dextrine. When this development has reached the projjer point, the germ is 

 killed by drying. The grain is then cleaned and crushed and placed in warm 

 Tvater to allow the diastase to act still further on the starch, the completion of this 



