May 3o, 1918 Hydration Capacity of Gluten 41 5 



determined to any great extent by the inorganic material present in the 

 flour. The soluble ash and specific conductivity are almost parallel to 

 each other in every case. This was to be expected, since the determina- 

 tions were made on identical flour extracts. 



The bread baked from the weak flours was of poor texture. In each 

 case the dough lacked the coherency and elasticity necessary to produce 

 "large well-piled" loaves. This is without doubt partially but not 

 entirely accounted for by the lower gluten content of these flours. 



WHAT DETERMINES THE PHYSICAL STATE OF THE GLUTEN 



Upson and Calvin (14, 15) believe the differences between strong and 

 weak glutens to be due to acids or salts in the flour, but it has been 

 shown earlier in this paper that there is no evidence for such an assump- 

 tion. 



Wood (17) likewise states that the physical properties of the gluten 

 are due — 



to varying concentrations of acid and soluble salts in the natural surroundings of the 

 gluten. 



This would appear to be identical with the view of Upson and Calvin, 

 but while Upson and Calvin believe that the controlling factors are pres- 

 ent in the flour. Wood (17, p. 274) believes that the character of the 

 gluten is altered at the time when it is laid down in the wheat kernel. 



It must be decided at what stage the acids and salts influence the gluten so as to 

 mpress upon it the physical characters which decide the physical character of the- 

 flour. I take it that this must occtu" when the endosperm is being formed, at which 

 time the grain contains much more water than when it is ready to grind. 



Wood and Hardy (17) suggest that each particle in a gluten hydrosol 

 is surrounded by an electric double layer and that the — 



tenacity, ductility, and water-content of a solid mass of moist gluten depends upon 

 the total or partial disappearance of these electric double layers, and the reappear 

 ance of what is otherwise obscured by them, namely, the adhesion or "idio attrac- 

 tion, " as Graham called it, of the colloid particles for each other, which makes them 

 cohere when they come together — ^the most complete coagulation, i. e., mechanically 

 the densest and most coherent coagulum being formed at the isoelectric point. 



However, in all of the papers by Wood or Hardy the assumption is 

 apparently made that at the isoelectric point all glutens are identical 

 in physico-chemical properties. This we do not believe to be the case, 

 for if all glutens were identical at the isoelectric point and the degree of 

 hydration, etc., were regulated by the presence or absence of electric 

 double layers around the colloidal particles, we should expect to find 

 approximately the same maximum hydration capacity for each gluten 

 preparation, although the maximum point on the hydration curves 

 might be reached at different concentrations of acids. We have already 

 shown that the glutens from different sources differ in rate of hydration 

 and in their maximum hydration capacity, and we believe that these 



