Enhancing gamma-aminobutyric acid content in germinated brown rice by repeated treatment of soaking and incubation

Abstract

Gamma-aminobutyric acid (GABA), commonly produced by germination of brown rice grain, is a free amino acid which could help relieving or preventing non-communicable diseases in human. Several research works have been conducted on GABA production from germinated brown rice. However, the yielded GABA (10.1–69.2 mg/100 g germinated brown rice) was comparatively low; thus the amount was insufficient to be used as active ingredients in functional foods. The objective of this study was to explore alternative methods in order to gain higher yield of GABA. A new process of repeated soaking (in tap water at 35 °C, 3 h) and incubation (at 37 °C, 21 h) during germination was developed. The amount of GABA produced was highest at 116.88 ± 9.24 mg/100 g germinated brown rice (dry basis). However, an unpleasant odour was generated by some microorganisms during long germination. Lactic acid was applied at soaking step to overcome this problem; whereby 0.5% lactic acid solution (vol./vol.) could effectively control the microorganisms without impairing GABA producing ability and sensory qualities.