Automated Determination of Tryptophan in Legumes and Cereals
Date of Original Version
An automated procedure for tryptophan determination in full-fat legumes and cereals was developed that included a modification of the p-dimethylaminobenzaldehyde (DAB) reaction. Minimal sample preparation was required. Samples were either hydrolyzed in 5 N KOH for 3 h for accurate determination or homogenized for 30 s for direct screening (25 samples/h). Reactants entered the manifold as follows: 0.16 ml/min sample (0.7-2 mg of protein/ml, 1 M KCl, pH 6 ± 0.5), 0.43 ml/min DAB reagent (0.154 M p-dimethylaminobenzaldehyde, 3 N HC1, 14 N H2SO4), and 0.32 ml/min dioxane reagent (p-dioxane-n-butyric acid-water, 2:2:1) 60 s later. Color absorbance (570 nm) was read 100 s after addition of dioxane. Values (coefficient of variation 5-10%) for casein, peanut flour, whole peanuts, soybean, wheat, oats, and sorghum agreed closely with those reported in the literature. © 1977, American Chemical Society. All rights reserved.
Journal of Agricultural and Food Chemistry
Amaya-F., Jaime, Clinton O. Chichester, and Clyde T. Young. "Automated Determination of Tryptophan in Legumes and Cereals." Journal of Agricultural and Food Chemistry 25, 1 (1977): 139-143. doi:10.1021/jf60209a027.