Abstract:γ-Aminobutyric acid (GABA) is an active substance with several physiological functions. Its content is generally low in grains, but GABA can be effectively enriched by stress treatments. In this study, the effects of combined treatments using citric acid and spermidine on the GABA content in buckwheat sprouts were studied, and the mechanism was preliminarily analyzed. Response surface optimization experiments showed that the combination of 2 mmol/L citric acid and 0.1 mmol/L spermidine was more conducive to the accumulation of GABA during buckwheat germination, and the GABA content could reach 12.23 mg/g, which was 1.11 and 1.27 times higher than that of single treatments with citric acid and spermidine, respectively. Simultaneously, the activities of glutamate decarboxylase (GAD), diamine oxidase (DAO) and polyamine oxidase (PAO) under combined treatments were investigated to analyze the reasons for the GABA content variations. The results indicated that the activities of the three key enzymes after treatments were 1204 nmol/(min.g), 18.92 U/g and 3.58 U/g, respectively, which were significantly higher than those of groups with no or single treatments. The results suggest that the combined treatment with citric acid and spermidine significantly increases the GABA content of buckwheat sprouts. This is related to the increase in the enzyme activities of GAD, DAO and PAO, which are the key enzymes in the GABA synthesis pathway, and the combined treatment exhibits a certain synergistic effect. This study provides ideas and theoretical basis for enriching GABA in grains.
