16 BULLETIN 717, U. S, DEPARTMENT OF AGEICULTURE. 



the protein^ of wheat flour was 93.8 per cent digested, the protein^ of 

 orange 85 per cent, and the protein ^ of butter was 97 per cent 

 digested. 



It is, of course, recognized that the calculated values so obtained? 

 for a special food, in this case soy-bean and peanut proteins, are 

 probably somewhat low, since they include the errors due to consider- 

 ing all fecal nitrogen not resulting from the accessory foods as undi- 

 gested soy-bean or peanut nitrogen, whereas fecal nitrogen, as has 

 been pointed out by Woods and Merrill,^ Crowther and Woodman,* 

 and others,' is derived in part at least from bile residues, epithelial 

 waste, stomach residues, mucus, and saliva. It is not believed, 

 however, that in this instance the error occasioned by the inability to 

 correct for this factor is significant, especially in view of the unusually 

 large quantities of soy-bean or peanut proteins consumed. 



THE DIGESTIBILITY OF PROTEIN SUPPLIED BY SOY-BEAN PRESS- 

 CAKE FLOUR. 



In spite of the very extensive use of soy beans by the oriental 

 peoples there appears to be little experimental data reported regard- 

 ing the digestibOity of the proteins suppUed by this protein-rich 

 legume. However, the long use of the soy bean as a staple article 

 of the diet by the Japanese and Chinese offers suflBicient evidence that 

 soy-bean protein is well tolerated by the human body. Oshima in a 

 summary of Japanese nutrition investigations, which includes much 

 interesting information regarding the digestibility of preparations of 

 legumes in common use in Japan, reports three experiments ^ in which 

 the subjects ate approximately 200 grams of tofu (soy-bean curd) 

 daily in conjunction with cooked rice. The average digestibility of 

 the total protein supplied by these diets, of which 83 per cent was 

 soy-bean protein, was 95 per cent. 



Few studies of the digestibility of soy-bean protein have been made 

 in this country. Mendel and Fine report ® an experiment of six days' 

 duration in which soy beans supplied 90.5 per cent of the total 

 nitrogen intake, the basal ration consisting of tomatoes, apples, 

 oranges, milk, sugar, and butter. The soy beans were boded in water 

 for one-half hour and the tomatoes thoroughly incorporated with the 

 resulting mush winch had been salted to taste. The total nitrogen 

 supphed by the diet was 85.3 per cent digested. The subject re- 

 ported that he was in excellent condition throughout the whole 

 experiment. Defecation was regular and no physiological disturb- 

 ances were experienced. The same authors conducted two series of 



1 U. S. Dept. Agr., Office Expt. Stas. Bui. 143 (1904), p. 32. 



« Connecticut Storr's Sta. Rpt. 1899, p. 104. 



a U. S. Dept. Agr., Office Expt. Stas. Bui. 143 (1904), p. 57. 



* Jour. Agr. Sci., 8 (1917), pp. 429-477, Part IV. 



6 U. S. Dept. Agr., Office Expt. Stas. Bui. 159 (1905), pp. 224. 



« Jour. Biol. Chem., 10 (1911), pp. 43^-458. 



i 



