USES OF CEREALS 553 



The chief constituents of flour are starch and gluten, 

 which are found in an average proportion of about 88 parts 

 of starch and 12 of gluten. The gluten may run as low as 

 6 to 8 per cent in California Club wheat, and as high as 

 14 or 15 per cent in Kansas hard winter wheat, and even 

 higher occasionally in durum wheats. Geographically 

 considered, the wheats of the Great Plains and certain 

 small parts of western intermountain districts have the 

 highest gluten content, while those of the eastern, south- 

 ern, and Pacific Coast states are lowest in percentage of 

 gluten. 



597. Essentials in the composition of flour. In addi- 

 tion to starch and protein (forming the gluten), flour 

 contains other carbohydrates and ash in small quantities 

 which are of considerable value. The most important 

 constituent is the gluten, both from the nutritive stand- 

 point, as it is always present in limited quantity even when 

 most abundant, and because of the necessary part it takes 

 in the formation of the loaf of bread. Gluten is a complex 

 substance, and, as previously stated (12) does not exist as 

 such in the flour, but is formed from several proteins and 

 the addition of water. The quantity of gluten is no more 

 important in loaf construction than the quality, which 

 is dependent upon the relative amounts present of its two 

 main constituents, gliadin and glutenin. The normal pro- 

 portion of these substances is about 65 per cent of gliadin to 

 35 per cent of glutenin. The former is the sticky element, 

 and, if present in excessive quantity, causes the dough to 

 become soft and "runny." If there is an excess of glutenin, 

 the dough becomes too stiff and rises slowly. Guthrie 

 (1896) demonstrated some time ago that it is the glutenin 

 of the gluten that has the greater absorption of water. 

 If, therefore, the gluten content of two flours is about 



