J 8 THE PROTEINS OF THE; WHEAT KERNEL. 



THE AQUEOUS EXTRACT OF WHEAT FLOUR. 



The water-extract of wheat flour is of a straw-yellow color, becoming red- 

 brown on standing, and has a very slight acid reaction towards litmus. 



Saturated with ammonium sulphate, a bulky precipitate forms, which on 

 standing contracts, showing the solution to contain but a small amount of 

 protein matter. After 24 hours this precipitate can be completely dissolved 

 in water, giving no evidence of the formation of insoluble derivatives. Sat- 

 uration with sodium chloride gives a small precipitate. Acetic acid in the 

 cold solution gives no precipitate until sodium chloride is added. 



On slowly heating, the solution becomes turbid at 48 and yields a floccu- 

 lent coagulum at 52. After heating to 65 for some time and filtering, the 

 solution becomes turbid again at 73, flocks forming in very small amount 

 at 82. No more separation occurs on further heating the extract even to 

 boiling. The addition of a little acetic acid and sodium chloride gives a 

 small precipitate. The body coagulating at 52 forms the greater part of 

 the protein in solution. The complete coagulation of this protein is accom- 

 plished with difficulty, prolonged heating at 65 being necessary to cause it 

 to separate completely. The addition of sodium chloride greatly facilitates 

 the final coagulation. The temperature at which the flocculent coagulum 

 separates depends upon the rate of heating. Unless the solution is heated 

 very slowly, the point at which flocculation occurs is much above 52. 



When the sodium-chloride extract of the wheat flour is saturated with 

 ammonium sulphate and the precipitate redissolved, and its solution dialyzed 

 until all of the globulin has separated, the solution, when slowly heated in 

 a double water-bath, becomes turbid at 48 and flocks separate at 55. After 

 heating for some time at 65 and filtering off the coagulum, the solution, 

 when again heated, becomes turbid at 70 and a very minute amount of 

 flocculent coagulum forms at 80. Boiling the solution after filtering gives 

 no more precipitate, and nothing is obtained by adding a little salt and acetic 

 acid. If the amount of salt is increased and acetic acid added, a precipitate 

 results. Kqual volumes of a solution so prepared were treated with 20 per 

 cent of sodium chloride and a little acetic acid. To the first the salt and 

 acid were added directly, to the second after heating to 65 and filtering off 

 the coagulum, and to the third after heating to 95 and likewise filtering. 

 The first portion gave the most precipitate, the last the least, showing that the 

 coagulable proteins are thus precipitated by salt and acid. The filtrate from 

 the first portion when neutralized and boiled gave no precipitate, indicating 

 that the separation of the albumin was complete. 



The above solution, freed from globulins by dialysis, gave a precipitate 

 on saturation with sodium chloride, the filtrate from which became turbid 



