28 



THE BOOK OF WHEAT 



Composition as Affected by Light. Light is essential for 

 the formation of proteids. The following table shows the 

 effect of differently colored glasses upon the nitrogen and 

 albumen content of wheat. 1 



Climate, soil and culture are also all factors that affect the 

 chemical composition of wheat. They are treated more fully 

 in subsequent chapters. 



The Composition of Different Commercial Grades of wheat 

 shows that the amounts of protein and ash decrease as the grade 

 of wheat becomes higher, while the nitrogen free extract in- 

 creases. Differences in protein, gluten or gliadin content do 

 not seem to be an adequate basis, however, for the commercial 

 grading of wheat. The grading seems to be based rather on 

 the relative yield of first quality flour. The greater the 

 weight of the kernel and the weight per bushel, the higher is 

 the grade of the wheat. 



Historically there has been little change in the chemical com- 

 position of wheat. It seems likely that the wheat of ancient 

 Egypt did not differ more in composition from modern wheat 

 of the same variety than one sample of modern wheat fre- 

 quently differs from another. 



1 Sci. Amer.. 93 (1905): 508. - 



