Respiration, Aeration, and Fermentation 299 



gluten of wheat flour, is the important factor in light- 

 bread making. It is of interest to note that anaerobic 

 respiration in higher plants results in the production of a 

 small amount of alcohol, so that the two processes are 

 comparable. 



174. Acetic fermentation. Acetic fermentation in 

 nature generally follows the alcoholic, and it is brought 

 about by the so-called acetic bacteria. These organisms 

 effect the oxidation of ethyl alcohol in weak solution to 

 acetic acid, probably in two steps, with the following, 

 general result : - 



C 2 H 5 OH + O, = CHaCOOH + H 2 O 



ethyl alcohol acetic acid 



At the same time some alcohol is utilized and COo pro- 

 duced. In commercial vinegar-making, cider, weak wine, 

 and other products of this nature are utilized, and there is 

 a slow and a quick method of procedure depending upon 

 the aeration. 1 



LABORATORY WORK 



Loss of weight. --Select two lots, each of 25 seed, of peas or beans. 

 Determine the dry-weight of one lot and record. Soak and ger- 

 minate the other lot in the dark closet upon a plate containing 

 moist filter paper. When the seedlings have grown about as 

 long as they will from the food material of the seed, determine 

 the dry-weight and compare with those ungerminated. 



Absorption of 2 and evolution of CO*. - - Into jars or wide 

 mouth bottles put some soaked or germinating seeds of peas or 

 beans, and cork tightly or seal. After a few hours, or next day, 



1 Prescott, S. C., "Wine, Cider, and Vinegar," Bailey's Cyclopedia of 

 American Agriculture, 2 : 181-186. 



