Dextrose Yield of Glycinin

Abstract

Since soy bean foods have been found to be useful in the diabetic dietary, 1 it was thought desirable to determine the dextrose conversion of soy bean protein.

Glycinin, a specific globulin, which constitutes 90-95% of the protein of the soy bean, 2 was prepared by a new method, since older methods were found to be tedious. Commercial soy bean flour was freed of fat by ether extraction. The residue was then suspended in water at a pH of 2-3, filtered, and the dissolved glycinin precipitated at its isoelectric point by adjusting the reaction to pH 4.7. The flocculent precipitate was washed with distilled water, redissolved at pH 2-3, filtered, and reprecipitated at pH 4.7. After washing, the precipitate was dried with alcohol and ether. This preparation contains 15.56% nitrogen, 5.5% moisture, 0.82% ash, and gives a negative Molisch test for carbohydrate.

Glucose yields were obtained on completely phlorizinized dogs, using the method applied by Janney 3 to the determination of glucose yields of other proteins. As a check on the method the yield of casein was also determined.

The average of 8 determinations of the glucose yield of glycinin, obtained on 5 dogs was 61%. The average of 11 determinations on 4 animals gave a glucose yield of 49% for casein, a figure which compares favorably with Janney's previous report of 48%.