Comparison of Orange G Dye, Formol Titration, and Kjeldahl Methods for Milk Protein Determinations

Abstract

A highly significant correlation of ~-0.975 between Orange G dye and Xjeldahl methods of protein determinations demonstrated that for most practical purposes the protein content of milk can be determined as effectively by the use of the rapid Orange G dye binding method as by the time-consuming Kjeldahl method. The correlation of ~-0.839 between the percentage of total protein determined by formol titration and the Kjeldahl method indicated that the Orange G dye method has an advantage in accuracy compared to formol titration as a rapid method for determination of protein in milk. This is, in part, due to effects from stage of lactation and month of the year on the formol factors for total protein.