THE DIGESTIBILITY OP BLEACHED FLOIIR. 
BY ELBERT W. ROCKWOOD. 
For several years the effects of the bleaching process upon the prop- 
erties of wheat Hour have been under discussion. The extent to which 
tionr is used as a food material demands that in justice towards the 
consumers through tests should be made to determine whether the process 
is deleterious or not. In this paper no consideration will be given to 
any aspect of the case except that of digestibility. 
AUhough at times a number of means have been employed to remove 
the natural yellow coloring matter from flour, and although several 
oxidizing agents will accomplish this result, at the present time the 
agent used in the great majority of mills is nitrogen peroxid. This may 
be generated from nitric acid but is usually produced by imssing a 
current of air through an electric arc, when the nitrogen is oxidized by 
the oxygen to nitrogen peroxid. The flour is passed through a mixture 
of this gas with a large excess of air, being agitated meam^diile. The 
yellow color is immediately destroyed. 
AYhen nitrogen peroxid comes in contact with water a mixture of 
nitrous and nitric acids is formed. In the bleached flour there remains 
a sul)stance which gives the reactions of a nitrite ; what its composition 
is has not been ascertained. The amount of such nitrite reacting sub- 
stance in commercially bleached flour varies ordinarily from less than 
one part to five or six parts of nitrogen in one million parts of flour. 
Food Commissioner Ladd of North Dakota has reported^ that poisonous 
materials are introduced in the bread in the bleaching process, naming 
particularly the nitrites. In conjunction with Bassett he has published"^ 
the results of digestion tests on bread where the bleached flour bread 
seemed to be more difficult of digestion than that made from unbleached 
flour. ShepaixT tested the action of nitrous acid on the digestive enzymes 
and found that while small amount did not interfere with their action 
U^add and Stallings, Bulletin 72. Experiment Station of North Dakota. 
November, 1906. 
Xadd and Bassett. Journal of Biological Chemistry, March, 1909. 
'^Shepard. Food Law Bulletin, III, 153. August 12, 1908. 
