1(3 



of flour when each is prepared from a different lot of wheat, because 

 of the wide variations in composition of different kinds of wheats. 



The investigations previously reported have shown that while the 

 coarser flours are somewhat superior as regards the total protein and 

 ash present they are inferior as regards digestibility, and that when 

 these facts are considered together the advantage from the standpoint 

 of nutritive value is with the finer flour. The earlier experiments 

 were made with wheats from widely different localities, including 

 Minnesota northern-grown hard spring wheat, Michigan soft winter 

 wheat, Indiana soft winter wheat, Oklahoma hard winter wheat, and 

 Oregon soft winter wheat, and it seemed important to determine 

 whether similar differences in the composition and digestibility of 

 bread from the different kinds of flour would be noted with flours 

 ground from other types of wheat and whether it was not fair to saj 

 that the differences observed were characteristic of all wheats, pro- 

 vided flours were ground from the same sample of grain. The wheats 

 selected for the present investigation were Oklahoma hard winter 

 wheat and Oregon soft winter wheat secured from the Oklahoma and 

 Oregon experiment stations, respectively. These are described in 

 detail beyond (p. 12). Portions of each lot were milled into straight- 

 grade, entire-wheat, and Graham flour, as described below, and the 

 digestibility and nutritive value of each determined from digestion 

 experiments with healthy young men. Furthermore, in order to ascer- 

 tain the influence on completeness of digestion of the bran and the germ, 

 generally removed in the milling of white flour, samples of bran and of 

 germ were prepared and added to successive samples of Oklahoma 

 straight-grade flour in about the same amounts as. were remov^ed during 

 the milling process, and the digestibility and nutritive value of bread 

 from these products likewise determined with the same subjects. 



MILLING THE SAMPLES OF WHEAT. 



The wheats used in the experiments previousl}^ reported were milled 

 in one of the large mills of Minneapolis and in smaller mills in Michi- 

 gan and Indiana, where somewhat different S3^stems of milling were 

 employed. Although the products of the different systems were of 

 the same general character, samples prepai'ed under uniform condi- 

 tions afford data for more definite and positive comparisons. Accord- 

 ingly, in the present investigation, a mill especially devised for 

 experimental purposes, and procured mainly for these experiments, 

 was used. The mill is provided with four sets of rollers, including 

 both corrugated and smooth rollers (illustrated in Plate I), and has 

 the essential features of a patent roller-process mill such as is used in 

 large milling plants. It is supplied with a bolting and sifting attach- 

 ment and is, in fact, a roller mill in miniature. By its use it is possible 



