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

Introduction: Many people are currently interested in improving and maintaining their health status by changing their dietary habits, like eating more natural foods; thus sprout products are becoming increasingly popular. In this context, sprouted brown rice grains are an excellent example of functional food, because besides their nutritive value, they also lower the risk of various diseases and/or exert healthpromoting effects. In this paper, we focused on the bioactive compound γ-aminobutyric acid (GABA) in germinated brown rice. GABA is known as an important amino acid that can help reduce hypertension and inhibit cancer cells development. Methods: We investigated the hydration characteristics of brown rice by drying them in a moisture analyser at 130°C until reaching a constant weight. The effects of soaking (duration and pH of soaking solution), as well as incubation conditions (temperature and time) on GABA biosynthesis in MangBuk brown rice of Vietnam were measured. Quantification of GABA was measured using a spectrophotometer. Results: GABA content in MangBuk type 1 brown rice was higher than in type 2. GABA content reached its highest value at 691.88 µg/g for type 1 rice and 596.48 µg/g for type 2 rice when MangBuk brown rice was soaked in a pH 7 water at 30°C for 12 hours, and then incubated at 35°C for 30 hours in aerobic condition. Conclusion: Germination conditions modified the content of biologically active compounds in MangBuk soft and hard rice varieties. GABA was synthesised during germination based on three factors, namely time of incubation, temperature of incubation, and pH of solution.