UDY DYE METHOD

General

Procedures and settings given for measuring whey protein in other sections of the manual are intended to give results comparable to Kjeldahl measurements. Because whey contains a significant and widely varying quantity of non-protein nitrogen (from 20 to 35% of the total nitrogen), Kjeldahl protein measurements are not accurate measurements of the true protein content. Since the UDY dye-binding method detects only the true protein, colorimeter settings may be used that do not include factors for the non-protein nitrogen.

Procedure

To determine the true protein in whey, use the same Reagent Dye volume and other procedural steps as given for milk with the following exceptions. The sample size and instrument settings to be used are given in the table below.

% Protein = A(C_I - C)