1902-3.] The Chemistry of Wheat Gluten. 511 



those of previous investigators, who had only in one instance obtained 

 from glutenin as much as 17 per cent, of nitrogen. 



Osborne considered it an altered form of gliadin, but the fact that 

 it has a definite coagulating point, while gliadin has none, would indi- 

 cate that it is improbable. No one has yet succeeded in making 

 gliadin assume a form at all resembling glutenin. In my opinion the 

 two proteids are entirely distinct in origin as well as in properties. 

 Osborne states that glutenin is slightly soluble in cold but much more 

 in hot dilute alcohol, the dissolved proteid separating on cooling. Since 

 glutenin is coagulated at about 70° C. the proteid dissolved must have 

 either been due to gliadin imperfectly separated from the glutenin, or to 

 part of the latter split off by heat. The trace soluble in cold alcohol, as 

 Osborne himself hints, may have been gliadin, which is exceedingly 

 difficult to separate from glutenin. 



V. — The Ferment Theory of Gluten Formation. 



The question whether gluten exists as such in flour, or whether it 

 results by the activity of a ferment, is one on which there are consider- 

 able differences of opinion. Weyl and Bischoff^° considered gluten to be 

 formed from pre-existing globulins by a pre-existing ferment in flour. 

 They held that flour extracted by 15 per cent, solution of sodium 

 chloride, and heated to the coagulation point of globulin, gave no gluten. 

 They were, however, unable to isolate the ferment. 



Martin'^ thought that gluten did not pre-exist in flour as such, but 

 that his gluten fibrin was derived from a precursor globulin, and his in- 

 soluble phytalbumose or gliadin, from a soluble albumose. He stated 

 that gliadin was not extracted directly from flour by 70 percent, alcohol. 



Johannsen^i advanced arguments against the ferment theory, and 

 thought gluten existed as such in a finely divided state in the wheat 

 grain. He stated that a temperature of 6o°C. did not injure the gluten- 

 forming po^ver of flour, and that flour made by mixing dry starch and 

 finely-powdered gluten behaved like ordinary flour. 



Ballard^^ maintained that gluten pre-existed as such in flour. 

 Osborne^^ arrived at the same conclusion. 0'Brien'^° found that flour 

 heated to 100° C. for thirteen hours gave practically the usual amounts 

 of gluten ; also that a paste made with boiling water yielded gluten in 

 apparently normal quantities : that flour left twenty-four hours under 

 absolute alcohol and ether, yielded gluten when these evaporated. He 

 concluded that there is but one compound soluble in alcohol, that the 



