Cereal Chem 51:610 - 615.  |  VIEW ARTICLE
A Modified Biuret Reagent for Determination of Protein.

J. S. Noll, D. H. Simmonds, and W. Bushuk. Copyright 1974 by the American Association of Cereal Chemists, Inc. 

Addition of isopropanol in equal volume to the alkaline cupric tartrate biuret reagent of Jennings yields a stable solution which reacts rapidly with protein, and is readily filterable. This reagent can be used to estimate protein content in whole grain meal and starch-rich samples as well as in dispersions containing urea and/or acetic acid. Correlation coefficients, using the Kjeldahl method as a standard, exceed 0.995, with a standard error of 0.08 mg. protein. The reagent was used successfully to quantify the fractionation of the protein in wheat meal and flour by two solubility fractionation procedures. Each fraction had a slightly different specific biuret color. Using an apparatus capable of providing high rates of heat transfer, the time for color development can be shortened to 60 sec. and the analysis can be automated. In this form the method has potential for rapid determination of protein in grain samples.