12 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE. 



Osborne and Mendel^ also report that they have been able to 

 demonstrate the presence of the water-soluble food accessory in 

 peanut meal. 



In summarizing the studies of the nature and value of soy-bean 

 and peanut proteins, referred to above, it appears first that chemical 

 analysis of glycinin and arachin shows them to be relatively rich in 

 lysine and tryptophane, amino acids essential for growth and main- 

 tenance, and second that studies of their biologic value show them to 

 be more efficient proteins than those supplied by the common cereals 

 or many of the common legumes. It appears then from these facts 

 that soy-bean and peanut proteins have a high nutritive value and 

 that further studies of their value in the human dietary are to be 

 desired. 



THE DIGESTIBILITY OF SOY-BEAN AND PEANUT PROTEINS. 



This investigation was undertaken for the purpose of determining 

 the digestibility of these proteins by normal individuals when eaten 

 as a constituent of a simple mixed diet. It is of course recognized 

 that the oil remaining in the soy-bean and peanut flours contributes 

 to the food value of these flours, but no special attention is given to 

 these oils in this study since previous studies of peanut ^ and soy-bean 

 oils ^ have shown that both are very well utilized by the human body. 



PREPARATION OF SOY-BEAN AND PEANUT PRESS-CAKE FLOURS.* 



The soy-bean flour used in the experiments which foUow was pre- 

 pared by expelling the oil from 2 bushels of weU-cleaned Mammoth 

 Yellow soy beans which had been grown under controlled experi- 

 mental conditions by Forage Crop Investigations of the Bureau of 

 Plant Industry. In order to secure a more nearly complete removal 

 of the oil than is usual, the cake was pressed a second time. The 

 press cake thus obtained was of a yellow color and retained about 8 

 per cent of oil. It was ground in a small-sized burr miU until all of 

 the meal passed through a millimeter sieve. Through the courtesy 

 of H. S. Bailey, of the Bureau of Chemistry, it was possible to pre- 

 pare both the soy-bean and peanut flours under conditions approxi- 

 mating those of the commercial oil miU, using for this purpose a 

 continuous process expeUer type of oil-expressing machine. 



In order to secure data relative to the fineness of this flour, a sam- 

 ple was bolted, and it was found that 53 per cent of the flour re- 

 mained on the 40-mesh sieve, 23 per cent remained on the 70-mesh 

 sieve, 9 per cent remained on the 90-mesh sieve, 3 per cent remained 



1 Jour. Biol. Chem., 32 (1917), No. 3, p. 310. 

 s U. S. Dept. Agr. Bui. 505 (1917), p. 18. 

 « U. S. Dept. Agr. Bui., 687 (1918), p. 6. 



< In this paper the term "flour" is used without reference to the coarseness of the ground soy-bean 

 and peanut press cakes. 



