WHEAT 



313 



acters being influenced by type, variety, soil, and season. 



383. Composition. The United States Department 



of Agriculture reports the composition of wheat as follows : 



TABLE 32. COMPOSITION OF WHEAT GRAIN AND WHEAT STRAW l 



An important constituent of the protein in the wheat 

 grain is gluten which is a mixture of the proteids gliadin 

 and glutenin. The gluten is directly responsible for that 

 property of wheat flour which causes it to form a porous 

 bread when mixed with water, leavened, and baked. The 

 gluten, being tenacious and elastic, imprisons the carbonic 

 acid gas caused by the fermentive action of the yeast, and 

 the expanding, imprisoned gas causes the bread to rise 

 and become porous. The bread-making qualities of wheat 

 are determined largely by both the amount and quality 

 of the gluten that it contains. The quality of gluten is 

 dependent upon the relative proportions of gliadin and 

 glutenin in its makeup, the most desirable proportion be- 

 ing from 65 to 75 per cent of the former and 25 to 35 per 

 cent of the latter. 



The composition of wheat, particularly as regards its 

 protein content, is greatly modified by seasonal conditions 

 and to a less extent by fertilizers. A survey of the experi- 

 mental evidence on this point reveals that the composition 

 of any given variety will be uniform from year to year 

 1 U. S. Dept. of Agr. Office of Exp. Sta. E. S., Bui. 11. 



