Free amino acids in dark- and white-muscle fish as determined by o-phthaldialdehyde precolumn derivatization

Abstract

Free amino acids in fish reflect microbial spoilage, and are precursors of biogenic amines, factors of health concern and indicators of fish decomposition. The objective of this research was to quantify levels of free histidine, lysine, ornithine and glutamine, which may become originators of highly undesirable histamine, cadaverine and putrescine in fish tissue. Liquid chromatography using o-phthaldialdehyde (OPA) pre-column derivatization, gradient elution and a C18 column were used for separation. Histidine was higher in white tissue of mahi-mahi and tuna than in red tissue. No significant difference in lysine levels was found between the two tissues of tuna. Glutamine and ornithine were higher in red tissue of mahi-mahi and tuna. Red snapper had higher levels of lysine than histidine.