THE CHEMISTRY OF THE STRENGTH 

 OF WHEAT FLOUR. 



By HERBERT ERNEST WOODMAN, Ph.D., D.Sc. 



{From, the Animal Nutrition Institute, School of Agriculture, 

 Cambridge University. ) 



It is well known that different flours vary enormously in respect of the 

 size and shape of loaf they yield on baking. The factor which determines 

 the quahty of flour in this connection has been termed "strength" and 

 the latter has been defined as "the capacity of flour for making large 

 well-piled loaves "(i). 



Many views have been held from time to time regarding the ex- 

 planation of flour strength from the chemical standpoint. The earliest 

 view was that strength was determined by the gluten content of the 

 flour, which by virtue of its tenacity was able to retain in the bread 

 the carbon dioxide produced as a result of the activity of the yeast. 

 Many cases, however, were investigated where flours possessing a high 

 gluten content were not so strong as a flour with a low content of gluten. 

 Furthermore, no accepted regularity has been found to exist between 

 the strength of flours and the water-holding or gas retaining capacity 

 of their glutens. 



Attention was next directed to the consideration of the individual 

 proteins in the gluten of flour, namely, gliadine and glutenine. It was 

 found that measurements of the absolute amounts of gliadine showed 

 no correlation with strength. Neither was it possible to show any con- 

 sistent relationsship between strength and the ratio of ghadine to glutenine 

 in the gluten. It was suggested by Hall (2) that gliadine might not be 

 a definite substance and that the gliadine contained in very strong 

 flours might be different from that in weak flours. Wood (3), however, 

 prepared and examined samples of gliadine from strong and weak flours 

 and concluded, on the grounds of their content of amide nitrogen, that 

 the proteins from both sources were identical. Indirect determinations 

 of the amide nitrogen of the glutenines of weak and strong flours led to 

 the conclusion that the glutenine protein in different flours was one and 



