Although several methods have been developed to make gamma-aminobutyric acid (GABA) accumulate in tea, the active ingredients and health benefits vary widely depending on the manufacturing process of tea products. In this study, the levels of bioactive compounds and antioxidant activity in tea leaves given the continuous anaerobic condition were investigated. GABA and other free amino acids such as alanine, valine, leucine, isoleucine, proline, and asparagine were increased in tea leaves after

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... naerobic treatment, whereas the contents of organic and fatty acids remained almost constant. Compared with untreated tea, anaerobically incubated tea possesses higher (-)-epigallocatechin and (-)-epigallocatechin gallate contents, and lower IC 50 values in the 1,1-diphenyl-2-picrylhydrazyl radical scavenging, superoxide radical scavenging, nitric oxide scavenging and xanthine oxidase inhibition assays, which may indicate that continuous anaerobic incubation enhances antioxidant activity. These results suggest that the continuous anaerobic treatment during manufacturing process may provide high quality GABA tea.