DENATURING OF VEGETABLE PROTEINS 45 



of edestin which had been obtained by extracting hemp-seed with a 

 solution of this salt at 60, a process which yields preparations consist- 

 ing chiefly of the more acid salt of this protein, which is to some ex- 

 tent hydrolysed when in solution. When this solution was heated to 

 boiling, a part of the edestin was coagulated. On removing the coagu- 

 lum and dialysing the solution the edestin was precipitated unchanged, 

 as shown by its complete crystallisation. When a very little acetic 

 acid was cautiously added to the filtrate from the coagulum and this 

 again heated to boiling, a second coagulum resulted at the same 

 temperature, namely, 95, as that at which the first coagulum began to 

 form. The coagulation in this case, as in the first, was still incomplete, 

 and the filtrate from the coagulum required a further addition of acid 

 in order to give a coagulum on again heating to boiling. From this 

 we might conclude that, in the complete absence of acid, edestin would 

 not be affected by simply heating its solution, were it not for the fact 

 that the writer has found that neutral edestin which contains no com- 

 bined acid whatever behaves in the same way as the edestin chloride. 



Some seed proteins, as, for instance, leucosin obtained from wheat, 

 are more easily coagulated than the seed globulins, but whether these 

 can be completely separated from their solution by heating to a few 

 degrees above the temperature at which a flocculent coagulum is 

 formed, is still an open question. The aqueous extract of wheat flour 

 becomes turbid on heating to 48 to 50 and a flocculent coagulum is 

 formed at 52. Whether the leucosin is thus completely coagulated 

 is difficult to decide, for after heating the solution for some time at 65 a 

 second but smaller coagulum begins to separate at 73, which gradually 

 increases in amount as the temperature is raised to 82. Above this 

 temperature no more coagulum is formed even on boiling. Whether 

 this second small coagulum, formed at the higher temperature, is a 

 residue of leucosin which remains uncoagulated at the lower temperature 

 or a distinctly different protein having a higher coagulation point, re- 

 mains to be determined. 



Most seed extracts behave in a similar manner on heating, and in 

 view of the incomplete coagulation of edestin and other seed proteins 

 it is a question whether or not the coagula obtained at the several 

 temperatures are really formed from different protein substances. The 

 temperature at which a coagulum separates in such solutions depends 

 much upon the rate of heating, and, unless the temperature is raised 

 very slowly, the first coagulum is obtained at a much higher degree. 

 The presence of sodium chloride in the aqueous extract of wheat flour 

 has little effect on the temperature at which the coagulum separates. 



