DIGESTTBILITY OF SOY-BEAN AND PEANUT FLOURS. 5 



or by ascertaining the biologic value of the protein by means of care- 

 fully controlled feeding experiments with laboratory animals. Such 

 experiments give data regarding the ability of a protein to support 

 normal life processes, such as growth, maintenance, and reproduction. 

 The amount of protein retained for body uses from the food eaten is 

 generally determined by digestion experiments in which the protein 

 under consideration appears as the sole or major portion of the protein 

 in the diet. 



The amount of protein supplied by soy-bean and peanut press-cake 

 flours would obviously vary somewhat with the varieties of the 

 legumes from which the flours were made and with the process of 

 manufacture. Proximate analysis of the dried soy beans and pea- 

 nuts shows them to have the following composition: Soy beans,^ 

 water 9.9 per cent, protein 36.5 per cent, fat 17.5 per cent, carbo- 

 hydrates 30.8 per cent, and ash 5.3 per cent, the fuel value being 

 approximately 1,950 calories per pound; peanuts^, water 9.2 per 

 cent, protein 25.8 per cent, fat 38.6 per cent, carbohydrates 24.4 

 per cent, and ash 2 per cent, the fuel value being approximately 

 2,480 calories per pound. When the oil is expressed from these 

 legumes the percentage of protein is correspondingly increased and 

 the resulting commercial press cakes ordinarily contain from 40 

 to 50 per cent of protein. The press cakes used in the study here 

 reported, which were obtained by expressing oil from soy beans 

 and peanuts in a small-sized expeUer type of oil press, contained a 

 larger amount of protein. But in any case the press cake should be 

 classed as protein-rich material and on the basis of chemical analysis 

 alone may well be considered as valuable food material. In order to 

 ascertain the true value of these proteins for dietary purposes it 

 is necessary to consider the factors referred to above, first, the 

 quahty of the protein as shown by the nature of the amino acids sup- 

 phed and by its biologic value, and second, the digestibility of the 

 protein. 



THE AMINO ACIDS SUPPLIED BY SOY-BEAN AND PEANUT PROTEINS AS 

 COMPARED WITH THOSE SUPPLIED BY COMMON CEREAL PROTEINS. 



Since in the commercial utilization of soy-bean and peanut flours as 

 human food these flours would, in all probability, be grouped with 

 the cereal flours and meals, it is natural to compare the amino acids 

 obtained from glycinin, the principal protein of soy beans, and 

 arachin, the principal protein of peanuts, with gliadin, zein, rye-pro- 

 lamin, oryzinin, and hordein, the principal proteins of wheat, corn, 

 rye, rice, and barley, respectively. 



1 Personal communication, average of 121 analyses reported by Forage Crop Investigations, Bureau 

 Plant Industry. 

 « U. S. Dept. Agr., Office Expt. Stas. Bui. 28 (1899), pp. 75. 



