Germination Time Dependence of Bioactive Compounds and Antioxidant Activity in Germinated Rough Rice (Oryza sativa L.)

Problem statement: Germinated rice has been recognized as a functional food and its health benefits. However, most related studies were on germinated brown rice but our previous study indicated that germination of rough rice was an effective method to obtain high concentrations of bioactive compounds. Germination time is one of the most important factors affecting the level of biochemical compositions and antioxidant activity. Approach: Rough rice seeds were soaked in water for 2 days and germinated for four different days (1- 4 days). Total phenolic compounds, phytic acid,α-tocopherol, γ-tocopherol, α-tocotrienol and γ-oryzanol were investigated compared with those of ungerminated brown rice. The antioxidant activity of germinated rice was evaluated through four different methods, the 1, 1-Diphenyl-2-Picrylhydrazyl (DPPH) free radical scavenging assay, hydroxyl radical scavenging activity, lipid peroxidation assay and linoleic acid emulsion system-thiocyanate method. Results: The results showed that the germination for 2 days or longer, after soaking, yielded significantly higher level of total phenolic, α-tocopherol, γ-tocopherol, α-tocotrienol and γ-oryzanol than those of ungerminated brown rice and soaked rice, whilst the concentration of phytic acid was reduced significantly when germination time was increased. The samples germinated for one day or longer also revealed greater antioxidant activity than those of ungerminated rice. Conclusion: The level of bioactive compounds and antioxidant activity of germinated rough rice were affected by germination time. Germination for 2 and 3 days was the optimum time for germination rough rice to obtain high concentration of bioactive compounds and high antioxidant activity. The germination process of rough rice could be a potential method to obtain functional germinated rice flour with high bioactive compounds and health beneficial properties and could be applied to produce functional food products.