The Appropriate Condition for Increasing GABA in Corn for Health Food Production

Abstract

GABA (γ-aminobutyric acid) is an amino acid that serves as the inhibitory neurotrans-mitter in the brain. It has the effect of lowering blood pressure, relieving insomnia and reducing stress. GABA could be found in germinating seeds through the activity of Glutamic Acid Decarboxylase (GAD) with glutamic acid or glutamate salt as a precursor. This research aimed to test and select the appropriate process to increase GABA content in various corn varieties using as raw material in health food products. Three recommended corn varieties of the of the Department of Agriculture were used in this experiment, i.e waxy corn var. Chainat 84-1, sweet corn var. Chainat 7566 and sweet corn var. Songkhla 1. Factors affecting the activity of GAD enzyme in GABA synthesis were studied which were the soaking period, the suitable pH and the suitable amount of monosodium glutamate for increasing GABA. Results showed that variety of corn and soaking period influenced the increase of GABA content in corn seeds. Sweet corn has higher ability to synthesize GABA than waxy corn. Moreover, longer soaking period would generate more GABA in corn seed. GABA content in corn seeds was found to be higher under low acidic condition (pH 6.5) when provided with optimum amount of GAD precursor. Results also showed that sweet corn var. Songkhla 1 has the highest ability to convert glutamic acid to GABA by GAD. The overall suitable conditions for increasing GABA was soaking corn seed for 24 hrs in pH-6.5 water adjusted by citric acid 0.1 M with the addition of 0.5% of monosodium glutamate as GAD substrate. GABA in corn seeds would increase to 259.2 mg/100 g or 1,006 which was.75% higher than the initial GABA content in seeds at 23.42 mg/100 g, without any off-flavor taste suitable for using as raw material in the high GABA content food products.