Q TRANSACTIONS OF WAGNER 



80 



THE CHEMISTRY OF BREAD-MAKING 



properties is marked. Water, in bread-making, plays more than a merely 

 mechanical part, also, in the earlier stages of the process, where it serves as the 

 medium for the biologic and chemical changes associated with the leavening 

 of the dough. 



Protein is the name apphed to any one of a group of organic food con- 

 stituents of a highly complex nature, containing the elements carbon, hydrogen, 

 nitrogen, oxygen, and sulfur, and of vital importance as furnishing material 

 for the construction and repair of muscular tissue, functions which no other 

 food constituents can perform. The proteins are numerous, and are differen- 

 tiated from other nitrogen-containing organic bodies by being built up structur- 

 ally of units called amino-acids, of which quite a number have been isolated 

 and analyzed. One of the best known proteins is egg-albumen (egg-white). 

 The protein constituents of wheat flour are distinctive in not being represented 

 at all in animal tissues and in but few other cereals. The total protein content 

 of wheat flour is from nine to twelve per cent., which comprises the following 

 individual proteins in approximately the following percentages, according to 

 Osborne : 



Insoluble proteins : 



Gliadin 4.25 



Glutenin ' 4.37 



Soluble proteins : 



Globulin 0.7 



Albumin 0.4 



Proteose 0.3 



The mixture of gliadin and glutenin, which, as will be seen, are in roughly 

 equal proportions, is known as gluten. It is the gluten in the flour of any cereal 

 which gives to the dough the viscous properties which enable it to be used in 

 making leavened bread. Wheat flour and barley flour stand highest in this 

 respect, rye flour next (although in this case the gluten content is smaller 

 and the doughing quality is contributed to by the development of gummy con- 

 stituents of the carbohydrate group which are peculiar to rye flour), while 

 maize flour is very inferior, and in oats and rice no gluten is found, thus ac- 

 counting for the well-known fact that leavened bread cannot be made from 

 either of these flours alone. The formation of the gluten is due to the stickiness 

 of the ghadin binding together the insoluble and elastic particles of glutenin. 



