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

Abstract

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.

Effects of soaking duration and incubation conditions on GABA biosynthesis in MangBuk brown rice of Vietnam

“…Patil & Khan (2011) also reported that Korean giant embryo brown rice (Keunnunbyeo) incubated for 21 hours had the highest GABA content. Similar result was also recently found by Zhang et al (2022), who showed that Chinese brown rice germinated for 24 hours with pulsed light exposure gave the highest GABA content. However, working on three varieties of Southern Thai brown rice, Banchuen et al (2010) suggested that the optimum conditions for producing the highest GABA content were to germinate them in a closed vessel for 36 hours for Sangyod Phatthalung rice and Chiang Phatthalung rice, and for 48 hours for Niaw Dam Peak Dam rice.…”

Proposing Signaling Molecules as Key Optimization Targets for Intensifying the Phytochemical Biosynthesis Induced by Emerging Nonthermal Stress Pretreatments of Plant-Based Foods: A Focus on γ-Aminobutyric Acid

“…PL treatments during germination or immediately after soaking could induce the increase in GABA contents of WBR grains, attributed to the PL-induced increase in Glu and GAD activity. 69 The fact that GABA biosynthesis of Arabidopsis was greatly accumulated after high light stresses were recently explained as the acclimation response. 70 The enhanced GABA accumulation by PL was related to the up-regulated expression of GAD1 and GAD3, with 4.64-and 29.03-fold increases, respectively.…”

Pulsed light treatment enhances starch hydrolysis and improves starch physicochemical properties of germinated brown rice

“…After sterilizing, seeds were rinsed with sterile water until pH was neutral, drained, placed in sterile water at a ratio of 1:3 (w/v) and left to soak for 3 h at 28 °C in an artificial climate chamber. 16…”

“…This is a result of their ability to enhance the extractability of bioactive compounds and improve the accessibility of relevant enzymes to substrates by disrupting the cell wall in the bran layer 11,12 . Some notable physical methods include hydrostatic pressure, 12 low‐pressure plasma, 13 ultrasound, 14 ozone, 6 electric field, 15 pulsed light treatment (PLT) 16 and static magnetic field (SMF) 17 . Among these, PLT is particularly noteworthy; it employs a broad spectrum of light, typically in the range of 100–1100 nm 18 .…”