JOMAL OF AGlilCimiRAL RESEARCH 



Vol. XII Washington, D. C, January 7, 191 8 No. i 



EFFECT OF TIME OF DIGESTION ON THE HYDROLYSIS 

 OF CASEIN IN THE PRESENCE OF STARCH ' 



By J. S. McHarguE, 

 Chemist, Laboratory of Chemical Research, Kentucky Agricultural Experiment 



Station 



The Van Slyke ^ method for protein analysis was worked out upon 

 mixtures of relatively pure amino acids and was not intended to be applied *-'-kt- 

 directly to crude sources of protein contained in cereals and feeding 

 stuffs. 



Notwithstanding this fact, Grindley, Slater, et al.,^ of the Illinois Experi- 

 ment Station, published in 191 5 the results of the determination of the 

 amino acids contained in cottonseed meal, tankage, and alfalfa hay, 

 applying the Van Slyke method directly to the proteins contained in 

 these different feeds. 



In the same month of 191 5 Nollau,* of this Station, published his results, 

 obtained by the Van Slyke method, on about 25 different sources of crude 

 protein contained in various seeds and feeding stuffs. 



In December, 1915, Grindley, Slater, et al.,^ published a second paper 

 on the amino-acid content of various feeds, including wheat, oats, barley, 

 and sov beans, a number of which had been analyzed by Nollau. The 

 summary of their second paper in part is as follows : 



The results here reported confirm the conclusion previously drawn, namely, that 

 the Van Slyke method for the determination of the chemical groups characteristic 

 of the amino acids of proteins can be applied directly to the quantitative determina- 

 tions of the amino acids of feeding stuffs with at least a fair degree of accuracy. 



Tne results which we have obtained for the quantitative determinations of amino 

 acids in feeding stuffs, on the whole, do not agree well with those recently published 

 by Nollau. In some determinations the results from the two sources are quite satis- 

 factory, but in many cases the agreement is far from satisfactory. The lack of con- 



• Approved for publication in the Journal of Agricultural Research by A. M. Peter, Acting Director, 



Kentucky Agricultural Experiment Station. 



^ Van Slyke, D. D. the analysis of proteins by determination of the chemical groups char- 

 acteristic OF THE DIFFERENT AMINO ACIDS. In Jour. Biol. Chem., v. lo, no. i, p. 15-53. 2 fig. 1911. 



' Grindley, H. S., Slater, M. E., et al. the quantitative determination of the amino acids of 

 FEEDING STUFFS BY THE VAN SLYKE METHOD. In J OUT. Amer. Chem. Soc, V. 37, no. 7, p. 1778-1781; 

 no. 12, p. 2762-2769. 1915. 



* Nollau, E. H. the AMiNO-AaD content of certain commeroal feeding stuffs and other 

 SOURCES of protein. In Jour. Biol. Chem., v. 21, no. 3, p. 611-614. 1915. 



Journal of Agricultural Research, Vol. XII, No. i 



Washington, D. C. Jan. 7, 1918 



U Key No. Ky.— 6 



(I) 



