Implementation of HPLC Analysis for γ-Aminobutyric Acid (GABA) in Fermented Food Matrices

In this study, a high-performance liquid chromatography (HPLC) method was adapted to measure the gamma-aminobutyric acid (GABA) and glutamate (Glu) content in different fermented foods. The best solvent to extract GABA and Glu from the food matrices was 75% EtOH and water, combined with 4% SSA as posttreatment. The extracted amino acids were derivatized with o-phthalaldehyde (OPA) for 2 min at room temperature and analyzed by HPLC with fluorescence detector (lambda ex = 340 nm and lambda em = 455 nm). Animal-based fermented products had a higher GABA content, compared with plant-based and soy-based fermented products. Among 17 fermented samples, fish sauce showed the highest amount of GABA (16.29 +/- 0.53 mg/kg DW). Results obtained by the HPLC method were compared with those obtained by a spectrophotometric method, which is based on the reaction of omega-amino acids with phenol. All measured GABA contents, obtained by HPLC method, were much lower than those obtained by the spectrophotometric method, which was due to the nonspecific reaction of the coloring reagent with other amino acids than GABA. It can be concluded that GABA content in food products can only be measured by HPLC.