13 



duces ail inferior quality of bread. The sample was ground in the same way as the 

 bran. 



No. 415. Bran tlour. The sample was prepared by adding 14 per cent of finely 

 ground bran (No. 413) to the straight-gra<le Oklahoma (lour (No. 27(5). 



No. 416. Germ fiour. The sample was prepared by mixing 93 per cent of straight- 

 grade Oklahoma flour (No. 276) witli 7 per cent of finely ground germ (No. 414). 



COMPOSITION OF SAMPLES OF WHEATS AND FLOURS. 



Complete proximate analyses of all of the wheat and flour samples 

 were made aceordino- to the methods recommended by the Association 

 of Othcial Aoricultiiral Chemists." The protein content was calcu- 

 lated by the use of two factors, namel}', 5.7 and 6.25. Investio-ations 

 have shown that the principal wheat proteids contain al)()ut 1T.<> j)er 

 cent nitrog-en instead of 16 per cent, the value upon which the factor 

 6.25 is l)ased, which is commonly used for calculating protein from 

 nitrogen. The use of the factor 5.7 gives lower values for the pro- 

 tein, })nt the results undoubtedly represent more nearly the actual 

 amoujit in the wheat than that obtained by the factor 6.25. However, 

 for the sake of comparison with investigations previously reported in 

 which the factor 6.25 was used, the protein is also computed b}' the 

 use of this factor. The carbohydrates determined by dilierence are 

 also estimated on the basis of protein as computed by both factors. 

 The heat of combustion was determined by combustion in a Berthelot- 

 Atwater bomb calorimeter, as described in a former publication.* In 

 the case of the milk samples weighed blocks of cellulose were eniplo3'ed 

 to absorb the li(iuid, according to the method described in a former 

 report.^ The calculated heats of combustion of the wheat and flour 

 samples were obtained by the use of the following factors: Protein, 

 5.!^, fat, I*.?); and carbohydrates, -t. 2 calories per gram. Earlier inves- 

 tigations have shown that when the principal nuti'ients of wheat flour 

 were separated, purified, and burned in the calorimeter they yielded 

 the following values per gram: Wheat staivli 4.190 calories, wheat fat 

 9.282 calories, gliadin 5.92-f calories, and glutenin 5.879'^ calories. 

 The calculated and determined heats of combustion of the flour samples 

 agree (piite closely, though the agreement is not perfect because of 

 the presence of cellulose and other substances which have a factor for 

 heat of combustion difjerent from that used in the calculation. 



« U. S. Dept. Agr., Division of Chemistry Bui. 46, revised edition. 

 ^U. S. Dept. Agr., Office of Plxperiment Stations Bnl. 101, p. 10. 

 cU. S. Dept. Agr., Office of Experiment Stations Bui. 126, p. 9. 

 <^U. S, Dept. Agr., Office of Experiment Stations Bui, 101, p. 13, 



