71 



poor baking quality invariably gave viscosity figures considerably 

 below those of good flours. 



The action of gliadin in gluten was also studied, and tlie viscosity 

 of gliadin solutions was found to be increased by traces of acids and 

 alkalis, and diminished by neutral salts. Further, the viscosity- of 

 gliadin solutions was greatly affected by change of temperature, and 

 it is interesting to observe that the temperature at which the 

 maximum viscosity was reached was also the temperature at which 

 the best doughs and breads are produced. 



The more recent work of Wood, on the action of acids and salts 

 on gluten, has already been briefly outlined in the First Report, but 

 his subsequent comments (Wood and Hardy, Proc. Roy. Soc, 1909, 

 B. 81, 38), made to bring the phenomena of the solubility of gluten 

 into harmony with the ionisation theory, cause rather a strain upon 

 the imagination. We may well believe that " the variations in 

 coherence, elasticity and water content, observed in gluten extracted 

 from difierent flours, are due rather to varying concentrations of 

 acid and soluble salts in the natural surroundings of the gluten than 

 to any intrinsic dififerences in the composition of the glutens them- 

 selves," but it is less easy to understand that the formation of aqueous 

 solutions of gluten " is due to the development of electric charges 

 round the particles of the proteid owing to chemical interaction 

 between proteid, acid, or alkaU, and water," and that the converse, 

 " 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 (supposed to surround each particle of solute), 

 and the reappearance of what is otherwise obscured by them, namely, 

 the adhesion, or ' idio attraction ' as Graham called it, of the coUoid 

 particles for each other, which makes them cohere when they come 

 together." This may be the explanation, but it does not help us 

 largely in predetermining the quaUty of the bread from any particular 

 flour, especially as the glutens were treated after washing out and 

 not in their normal surroundings. 



Weyl and Bischoff (Jago, " The Technology of Bread -snaking ") 

 showed that a flour moistened with a 15 per cent, sodium chloride 

 solution gave a dough that had lost its tenacity. Flour baked for 

 several hours at 60° C. can also not be doughed. Both experiments 

 have given rise to the theory that a ferment " myosin " is largely 

 responsible for the ultimate production of gluten during doughing. 



Distilled water dissolves a certain amount of gluten from flour, 

 and leaves the dough sticky rather than springy. Soft alkaline 

 water destroys the springiness of gluten by disintegration of the 

 gluten, and by prevention of the coherence of its particles. Hard 

 waters, especially those containmg much sulphates, harden the gluten 

 considerably. Chlorides generally are more gentle in their action and, 

 up to a point, assist the water-absorbing and retaining power of gluten. 



For other information concerning gluten and its components, 

 see also : — 



Jour. Amer. Chem. Soc, 263, Guess (1900); 1068, Snyder, and 1657, Cham- 

 berlain (1905) ; 8, Norton (1906); 74, Matthewson (1908); 1295, Upson & Calvin 

 (1915). 



