AMINO-ACIDS OF FLESH J\ 



Table II. Percentages of amino-acids. Giving the amount of 

 amino-acids in 100 g. of protein. 



Humin N shows a difference. It is, if anything, higher in the white meats, 

 e.g. breast of chicken 3 %, legs 1'3 %, pork 1-2 %, than in the red meats, 

 where the average is 0-5 %, except in the horse, where 0-9 % was found. The 

 explanation of this slightly higher value may be that the animal was nut 

 properly bled on slaughter. 



Lysine figures are, with the exception of mutton, higher for the red meats, 

 averaging about 11 %, while, of the white meats, rabbit limbs show only 5*5 %, 

 chicken breast 2 % and pork 7 %. 



Gortner and Holm [1920, 1], working with mixtures of pure amino-acids, 

 have shown that tryptophan, and in the presence of aldehyde also tyrosine, 

 and their analogues are the only known amino-acids which go to form humin. 

 There is therefore no connection between the humin content and the lysine 

 content of the meats; this is exemplified especially in the chicken, where the 

 humin is high, and the lysine is low in the breast; and humin is low and 

 lysine high in the legs. It may perhaps be mentioned that in the preparation 

 of the di-amino-acids by the method of Kossel and Patten a distinct yellowish 

 colouring adheres to the lysine portion. 



At the same time too much reliance must not be placed on the humin 

 as an estimation of tryptophan and tyrosine. Gortner and Holm [1920, 2] 

 and Thomas [1921] have shown that tyrosine and tryptophan which go to 

 form humin are not necessarily the only substances giving a reaction with the 

 phenol reagent of Folin and Denis. Estimations of substances giving the blue 

 colour with this reagent were made during the progress of this work, both 

 before the removal of the humin and afterwards. In the case of chicken 

 breast, a white meat, the readings before removal of the humin represented 

 4% "tyrosine" whereas after its removal the readings represented 3-5%. 

 In the case of beef however^a red meat — the difference was greater, the 

 former reading being 3-5 % and the latter 2-1 %, yet the humin N was much 

 lower in the case of beef. 



The arginine figures are more constant at about 14 or 15 % except in 

 rabbit fore limb and chicken legs where the average is 8 %. 



The histidine figures are less satisfactory, and exhibit perhaps a weak 

 point in the method. In this connection it is of interest to point out that in 

 the cases of abnormally high histidine the figures for the non-amino N are 

 lower than normal and vice versa, e.g. beef 5 % histidine, 28 % non-amino N, 



