Strength in Wheaten Flour. 



53 



ordinary distilled water it partly dissolves, the residue— the larger 

 portion — forming a semi-fluid sediment destitute of tenacity. 

 Why? Because tenacity and ductility are properties impressed 

 on gluten by something else — namely, by salts, by electrolytes, 

 that is, which may be organic and may therefore be unrepresented 

 in an ash analysis. 



This being the case, it is obvious that any attempt to correlate 

 strength with the physical properties of gluten washed out in the 

 ordinary way must end in failure, since the properties of washed 

 gluten depend upon the electrolytes which happen to be left in 

 after the washing is concluded. 



Electrolytes — that is to say, salts, acids, and alkalis — intervene 

 in two absolutely distinct ways. They control the physical pro- 

 perties of the gluten in the dough, and they must also profoundly 

 modify the temperature relations and the rapidity of the change 

 undergone by the gluten and other constituents of the dough in 

 the process of baking — a change which, so far as the proteins are 

 concerned, is, broadly speaking, a lowering of solubility. We 

 know something of the way in which they act on gluten in the 

 dough, but of the more complicated action during temperature 

 changes we know nothing ; it is possible that the same electrolyte 

 may increase the mechanical stability of the loaf in the dough and 

 yet diminish it in the oven. 



Let us turn to the action of electrolytes upon moist gluten, 

 that is, upon gluten as it exists in dough. 



Gluten prepared from wheat by washing the flour in many 

 changes of water is a stringy ductile body capable of retaining 

 bubbles of gas. When it is placed in dilute acid or alkali this 

 property vanishes. As little as i part of sulphuric or hydro- 

 chloric acid in 20,000, or 1 in 5,000 of acetic or lactic acid, will 

 disperse the gluten in fine particles. There is not only the loss 

 of actual cohesion ; the gluten particles are so changed that they 

 actually repel one another, and a non-settling milky suspension 

 is produced. In order to restore cohesion it is merely necessary 

 either to neutralise the acid or to add any salt such as common 

 table-salt. 



Any salt confers cohesion upon gluten ; any acid or alkali 

 when sufficiently dilute lessens or destroys it. Gluten itself seems 

 to be purely passive. 



The removal of salts by washing gluten with distilled water 

 will lower the forces which make for cohesion, so that less and less 

 acid is needed to neutralise them ; a point may be reached where 

 apparently any concentration of acid, no matter how low, is 

 sufficient. When gluten is thoroughly extracted with distilled 

 water it loses cohesion and disperses as a cloud, not owing to the 

 action of the water, but because of the faint acidity due to the 



