RAPID GAS-CHROMATOGRAPHIC SCREENING OF EDIBLE SEEDS, NUTS AND BEANS FOR NONPROTEIN AND PROTEIN AMINO-ACIDS

Water extraction with subsequent picric acid treatment and solvent washing (ethyl acetate and diethyl ether) was employed for the rapid isolation of free amino acids from non-aqueous food samples. The isolated amino acids were subjected to N(O,S)-isobutyloxycarbonylation followed by solid-phase extraction and tert.-butyldimethylsilylation for direct analysis by gas chromatography and gas chromatography-mass spectrometry. When the present method was applied to nineteen food samples (common beans, seeds, and nuts), seventeen protein amino acids and fifteen non-protein amino acids were simultaneously screened. Eleven non-protein amino acids including gamma-aminobutyric acid, pipecolic acid, pyroglutamic acid, alpha-aminobutyric acid, alpha-aminoadipic acid, and beta-alanine were tentatively identified, and four compounds assumed to be non-protein amino acids remained unidentified.