Effects of anaerobic fermentation in a nitrogen atmosphere on bioactive compound content in Vietnamese GABA tea
Authors: Quoc Sinh Nguyen*, Chi Bao Nguyen, Thanh Long Le, Sy Vuong Ho, Thi Diem Huong Nguyen, Van Quoc Bao Vo, Van Toan Nguyen
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Gamma(γ)-Aminobutyric acid (GABA), which provides a variety of health benefits, is an important bioactive component of tea (Camellia sinensis). A special tea product, GABA tea, contains high levels of γ-Aminobutyric acid which is produced by anaerobic fermentation. Tea fermentation is affected by a number of factors, including anaerobic conditions (vacuum, and the kind of gas used), temperature, and the duration of anaerobic fermentation. In this study, the levels of bioactive compounds in tea leaves produced by fermenting fresh tea leaves in nitrogen gas are investigated. The fermentation was conducted at different temperatures: room temperature (28±2), 35, and 40ºC; and for each temperature setting, the fermentation times were 6, 9, 12, and 15 hours. The results show that the GABA content increased significantly with fermentation temperature. The most appropriate temperature and time for the anaerobic fermentation to produce GABA and other bioactive compounds were, respectively, 40ºC and 9 hours. Under these conditions, GABA content reached the maximum value (202.77 mg/100 g of dry tea); that of total polyphenols was 22.30% of dry matter (DM); caffeine was 2.39% DM; and soluble solids were 36.25% DM.