A RAPID COLORIMETRIC METHOD FOR THE DETERMINATION OF TRYPTOPHANE IN PROTEINS AND FOODS

TL;DRAbstract

A survey of the literature shows that the values given by several investigators for the tryptophane content of certain proteins are twice those reported by others for the same protein.In practically all cases the high values were obtained by calorimetric methods in which the color developed was compared against that similarly obtained with casein, the value for the casein having been predetermined by the same procedure with free tryptophane as a standard.The tryptophane values for casein thus found ranged from 2 to 2.4 per cent.These high values for tryptophane in casein have been reported by May and Rose (1) and others (2-5) who used their method or modifications of it.On the other hand, Shaw and McFarlane (6), Block and Bolling (7), with different calorimetric procedures, and Greene and Black (8), by a microbiological method, found casein to contain from 1 to 1.20 per cent of tryptophane.Sullivan, Milone, and Everitt (4) developed a modification of the May and Rose method which great

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