148 PLANT PRODUCTS 



plant, and the composition of the reserve proteins appears 

 to vary more than does the composition of the proteins that 

 take part in the active life of the plant. Extraction with 

 somewhat diluted alcohol has been employed to remove some 

 of the proteins of cereal seeds, although in other seeds such 

 extraction with alcohol yields but little protein. Extraction 

 with alcohol can be made at any temperature up to its boiling 

 point, if the alcohol is sufficiently concentrated to inhibit 

 hydrolysis. By evaporating such a solution in fairly strong 

 alcohol, the alcohol evaporates first, the percentage of water 

 increases, and the proteins become insoluble. On the other 

 hand, from fairly concentrated solutions protein may also 

 be separated by adding absolute alcohol, since in absolute 

 alcohol proteins are insoluble. The addition of ether 

 assists in this precipitation of protein. Roughly speaking, 

 solutions containing less than 50 per cent, of alcohol, 

 or more than 93 per cent, of alcohol, do not dissolve cereal 

 proteins. Other alcohols than ethyl alcohol can be used for 

 solutions. Zein, from maize, can be dissolved in boiling 

 acetic acid without any apparent change, and is also particu- 

 larly resistant to the action of alkalies, even 2 per cent, 

 of potassium hydrate at 40 Cent, during 24 hours giving 

 little evidence of alteration. Zein also shows a unique 

 behaviour towards alcohol, because, when dissolved in strong 

 alcohol, the solution becomes gelatinated. In such circum- 

 stances, however, the original nature of the protein appears 

 to be permanently altered. The globulins differ in a marked 

 degree from the animal proteins, for most of them are very 

 incompletely coagulated by heating the solution, even to 

 boiling point. The vegetable proteins have a fairly marked 

 specific rotary power towards polarized light. Gliadin, 

 from wheat, rye, and barley, has a high rotary power, 

 corresponding to about 100 ; but zein, from maize, has 

 a relatively low specific rotary power of about 30. 

 The hydrolysis by acids of the vegetable proteins are of 

 much the same general character as those from the animal 

 proteins. The vegetable proteins are generally more difficult 

 to completely hydrolize than the animal proteins, and a 



