Application of the 2, 4, 6-Trinitrobenzene-1-Sulfonic Acid (TNBS) Method for Determination of Available Lysine in Maize Seed

Abstract

This paper reports on a modified procedure for determination of lysine in maize seeds. The modified procedure was economical, accurate and fast, and has been used to determine the available lysine in large numbers of maize grains. Protein sufficiently representative of total protein was extracted from samples ground in a water-cooled grinder. It was proposed that for samples with more than 15% protein the volume of NaOH-ETOH extractant be doubled. For maize samples with 15-30% oil content, 20ml of acetone was used for fat extraction, as opposed to 15 ml of acetone used for samples with less than 15% oil content. The sub-sampling variation was not significant for the modified 2, 4, 6-trinitrobenzene-1-sulfonic acid (TNBS) procedure. The correlation coefficient between lysine values determined by the amino acid analyser and the TNBS method for 90 opaque-2 samples was high (r=0.806). The coefficient of variation for TNBS was 6.5% against 12.6% for the microbiological assay (MBA), indicating that more variation was associated with the MBA than with the TNBS method.