Abstract: This study aimed to optimize the culture conditions for γ-aminobutyric acid (GABA) production in germinated quinoa under citric acid stress. GABA from germinated quinoa was ultrasonically extracted with ethanol and analyzed by high performance liquid chromatography (HPLC). The optimization of citric acid concentration, culture time and temperature, the factors affecting GABA content in germinated quinoa, were optimized by the combined use of one-factor-at-a-time method and response surface methodology. Results indicated that the highest GABA content of 1.538 mg/g in germinated quinoa was obtained after 48 h of culture at 25 ℃ in the presence of 2.00 mmol/L citric acid, which was 3.8 times as high as that observed for the ungerminated sample. The percentage of ACE inhibition by germinated quinoa under citric acid stress was 63%, which was 1.3 and 1.9 times higher than that that by the germinated one without citric acid stress and the ungerminated one, respectively. This finding suggested that germination under citric acid stress could improve the antihypertensive activity of quinoa, which will provide a guideline for further study of quinoa.

Key words: quinoa, germination, citric acid stress, γ-aminobutyric acid (GABA), response surface analysis