4 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTUEE. 



cotton unprofitable in many sections of the South and peanuts are 

 now grown as a supplementary crop. The recent increase in the 

 production of soy beans has probably resulted primarily from the 

 present great need of additional food materials for both human and 

 animal consumption. 



The present imperative demand for oils in the manufacture of 

 explosives, coupled with the increased demand for oils for industrial 

 and edible purposes, makes it highly probable that large quantities of 

 soy beans and peanuts will be pressed in cottonseed-oil mills where the 

 machinery is adapted for the expression of oil from these oil-bearing 

 seeds as well as cotton seed. 



It has been estimated^ that 150,000 bushels, or 9,000,000 pounds 

 of soy beans was pressed durmg the season (1917-18) in North 

 Carohna alone, which produced more than 3,500 tons of press cake. 

 In addition to the supply of domestic soy beans there are large 

 quantities of beans which have been imported from other coun- 

 tries. It is also reported ^ that the greater portion of the present 

 unusually large crop of peanuts wiU be pressed. The residue, which 

 remains after most of the oil has been removed from soy beans 

 and peanuts, commercially known as press cake, contains a high 

 percentage of protein. Such press cake has been very largely used 

 as stock feed and, because of its high nitrogen content, for fer- 

 tilizing purposes. It is at once apparent, however, that if care 

 were exercised in grading and cleaning sound soy beans and in shelling 

 and sorting sound peanuts, and if they were pressed under sanitary 

 conditions, the resulting press cakes should be of considerable value 

 for use as human food, and especially as a source of protein. Further- 

 more, since the oil is not fuUy extracted by pressing, the ''cakes" are 

 also an important source of fat. Thus it would seem that the extensive 

 studies which have already been made of the soy-bean and peanut 

 proteins are of a very definite value and that further studies of the 

 possible uses and value of high-grade soy-bean and peanut press cakes 

 for human food are to be desired. 



FACTORS CONSIDERED IN DETERMINING FOOD VALUE OF A PROTEIN. 



In considering the value of any material as a source of protein 

 for food purposes, at least three factors are ordinarily considered, 

 namely, the amount, the quality, and the digestibility of the protein 

 supplied by the material in question. The amount of the protein 

 present in the material under consideration is determined by chemical 

 analysis. The quahty of the protein ordinarily is determined by 

 either, or preferably both, of two methods: By ascertaining the num- 

 ber and nature of the amino acids making up the protein molecule, 



' Personal communication. Forage Crop Investigations, Bureau Plant Industry. 

 * Personal communication, Bureau of Chemistry. 



