Zur Bestimmung der biologischen Wertigkeit von Nahrungsproteinen

Abstract

The emphasis in this work is on plant proteins which form a large percentage of human food. Their biological value is determined by their content of the essential amino acids; often it is sufficient to estimate several key amino acids only, especially lysine, and also methionine, tryptophan and threonine. A colorimetric method for the estimation of lysine is here described. The protein hydrolysate is fractionated on Dowex columns, and lysine eluted together with arginine. The latter amino acid does not interfere in the subsequent reactions. The mixture is chlorinated with chloramine, and then treated with Folin reagent (sodium tungstate and sodium molybdate). The color is measured at 750 m[mu]. An accuracy of [plus or minus] 1% was obtained in the course of lysine estimations of 10 proteins.