The Tryptophan Content in Protein of Cereal Grains and Legume Seeds as a Function of Nitrogen Content

A Reappraisal of Tryptophan Score
  • S. Delhaye
  • J. Landry
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 398)


The tryptophan content ([Trp]) in the dry matter (DM) of wheat, maize, barley, sorghum, rice, pearl millet grains, pea and broad bean seeds is evaluated from samples, with various nitrogen contents ([N]DM) and genotypes, using a procedure that has been shown to be strictly quantitative.

The determination of linear correlations between [Trp]DM and [N]DM, and between the tryptophan content in protein ([Trp]N) and [N]DM or 1/[N]DM for every species leads to the following observations: (1) [Trp]DM and [N]DM are linearly related. The data show that previous reports of similar relationships underestimate tryptophan by 10 ± 5% owing to tryptophan degradation during alkaline hydrolysis preparatory to analysis; (2) the linear correlations between [Trp]N and 1/[N]DM, resulting from linear relationships [Trp]DM and [N]DM display coefficients of determination (r2) far lower than 1 and similar to those found for linear correlations between [Trp]N and [N]DM; (3) [Trp]N increases with [N]DM increasing for rice and pearl millet while it decreases for all other species.

In conclusion: (1) linear relationships between tryptophan and nitrogen have a low predictive value; (2) the nutritional score of tryptophan of foods and feeds, as calculated from the determination of tryptophan using a procedure involving alkaline hydrolysis, is generally underestimated by 10%.


Nitrogen Content Pearl Millet Broad Bean Phase High Performance Liquid Chromatography Legume Seed 
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Copyright information

© Plenum Press, New York 1996

Authors and Affiliations

  • S. Delhaye
    • 1
  • J. Landry
    • 1
  1. 1.Laboratoire de Chimie BiologiqueINRA, INA-PGThiverval GrignonFrance

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