Investigation Fermentation of Oolong for Stress Suppressing Drink and Enriching GABA—A Neurological Nourishing Compound

Nowadays, the modern living lifestyle made the number of stressful people increasing day by day. This strategy brought up a problem of overusing stress managing pills, whose side effects are weight gains, changes of appetite and sleep habits, frustration, etc. As a result, there is a need for natural antidepressant remedies for the community to reduce such stressful situations. Tea (Camellia sinensis) becomes one of the most popular drinks worldwide because of its effective medicinal properties such as antioxidant, antitumor, antidepression, cancer and cardiovascular diseases prevention, etc. However, fresh tea might be quite bitter due to high tannin content, hard to preserve and insomnia causing. Fortunately, fermented tea could be another better choice as it reduced tannin content, increased fragrant and eye-catching color, together with the richness of γ-aminobutyric acid (GABA), a neuro-benefit compound, could overcome those downsides. In this study, tea was screened for enzyme inactivation conditions, then fermented for good color ratios, lower tannin content, and higher GABA content. Oolong tea inoculated with 8% L. brevis and fermented in 4 days yielded better GABA content than fermentation of Oolong tea with and without Viscozyme L. Under these conditions, fermented tea had a good sensory assessment with color, flavor almost like Pu-erh tea. Other attributions of fermented tea would be TF/TR at 1/9.7, TC at 1.53%, tannin content at 13.72%, and GABA content at 302.38 mg/kg, almost 4 times higher than GABA content in raw material. This finding is a requisite for further production of GABA rich tea to create widely consuming and naturally stress suppressing drinks.