4 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE. 
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 eee or 9,000,000 pounds 
of soy beans was pressed Inne the season (1917- 18) in North 
Carolina 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 will 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 protemm. 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 fully extracted by pressing, the ‘‘cakes”’ are 
also an important source of fat. Thusit 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 quality 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, 
1 Personal communication, Forage Crop Investigations, Bureau’Plant Industry. 
2 Personal communication, Bureau of Chemistry. 
