Effects of pulsed light on germination and gamma-aminobutyric acid synthesis in brown rice

This study observed the effects of pulsed light (PL) on the germination and gamma-aminobutyric acid (GABA) production of brown rice and analyzed the correlations among glutamic acid (Glu) content, glutamate decarboxylase (GAD) activity, and GABA content in germinating brown rice. Both germination and GABA content were increased by exposure to PL, and this effect was evident when brown rice was exposed to PL immediately after being soaked. The PL group had significantly higher Glu and GABA content than the control check (CK) group which was unexposed to PL during the germination of brown rice. Glu content peaked at 18 h and GABA peaked at 24h in the PL group, which were 12 h and 6 h earlier than the CK group, respectively. GAD activity of the PL group peaked 12 h after germination, 6 h earlier than the CK group. PL exposure also increased the free amino acid content in the earliest stage of brown-rice germination. During brown-rice germination, the production of GABA is regulated by GAD activity and is significantly positively correlated with Glu content. PL treatment had a significant effect on GAD activity and Glu content during the germination process of brown rice and helped to increase its GABA content. Practical Application This study has shown that pulsed light exposure is an efficient and stable processing method for producing brown rice with high GABA. This will provide a new direction for developing novel germination grain foods.