[From THE BIOCHEMICAL JOURNAL Vol. XVI, No. 1, pp. 27— .30, 1922J (\ 



[Ail Rights reserved] 



VI. THE AMINO-ACIDS OF FLESH. 



THE DI-AMINO-ACID CONTENT OF RABBIT, CHICKEN, 

 OX, HORSE, SHEEP AND PIG MUSCLE. 



By JOHN LEWIS ROSEDALE. 



From the Biochemical Department, Rowett Research Institute for Animal 

 Nutrition, University of Aberdeen and North of Scotland College of Agri- 

 culture. 



{Received December 20th, 19'£1.) 



A LONG series of food analyses has recently been made by Plimmer [1921, 1], 

 who points out that by the ordinary routine method of analysis, in which 

 the amount of protein is estimated by multiplying the nitrogen content by 

 6-25, no discrimination is made between the flesh of different animals. The 

 protein of one animal is regarded as being the same as that of another. The 

 work of Emil Fischer and Kossel and their pupils has definitely proved that 

 the various proteins differ very widely in their composition as regards the 

 amino-acids, and this difference is emphasised by the experiments on the food 

 value of the individual amino-acids by Hopkins in conjunction with Willcock 

 and Ackroyd, by Osborne and Mendel and other American investigators^. 

 These chemical and biological differences are sufficient evidence that quality 

 of protein in nutrition must be taken into consideration. 



Complete analyses of the protein of the muscle of the ox, chicken, halibut 

 and scallop have been made by Osborne and Heyl [1908] and Osborne and 

 Jones [1909], and Drummond [1916] has made some analyses of muscular 

 tissue by Van Slyke's method. Both the more complete analyses by Osborne 

 and co-workers and those by Drummond do not show any marked difference 

 in the amino-acid content of the various muscle proteins. The flesh of various 

 animals shows such distinct appearances, different both to the eye and palate, 

 that it seems probable that greater differences may exist, and that there may 

 be smaller differences in the flesh from various parts of the same animal's 

 carcase, such as back and leg. Some further amino-acid analyses have there- 

 fore been made. 



The methods of protein analysis are far from perfect: Fischer's ester 

 method for the mono-amino-acids, as he pointed out, is not quantitative: 

 Kossel and Patten's method for the di-amino-acids, in spite of the numerous 

 manipulations, is generally considered to be fairly accurate, but it has been 

 largely superseded by Van Slyke's method which gives higher values for these 

 amino-acids. Van Slyke's method also possesses the advantage of requiring 

 only small amounts of protein and is more rapidly carried out. This method 

 of protein analysis has been used in these experiments, since it was chiefly 



^ See summary by Plimmer [1921, 2], 



