The tea farm is located in the Mingjian region, on the western edge of Taiwan's famous Nantou tea province. The climate in the region is subtropical, rather mild all year round, and has an average annual temperature of 22–25 degrees Celsius. The hilly landscape of Bagu Shan Mountain, in the west of Mingjian, is the source of our Classic GABA Oolong.
The tea leaves are harvested by hand in June, and those carefully selected for the tea are taken through the following process:
1. Withered for about 1.5 hours under the sun to reduce their moisture content and achieve slight oxidation. The leaves are turned 1–3 times to slow down the oxidation process.
2. Wilted indoors for 7–9 hours. The leaves are taken out of the sunlight to wilt indoors. They are evenly spread out at first and later layered. The leaves are tossed four times: twice lightly and twice rigourously for better evaporation and fermentation. The first cracks start to appear in the leaves at this stage, especially at the edges, which allows the cell sap to easily run out. Now separated from the intact cells, the enzymes (e.g. phenoloxidases) and other compounds, including polyphenols, start reacting with oxygen.
3. 8–15 minutes of "Big waves stirring". In this step, the plant cells are even more extensively broken up by intensive agitation: partly by machine, partly by hand. Here, oxidation is promoted.
4. Oxidised for 3–4 hours. The tea leaves are piled up to a layer of about 5cm to store heat and to promote oxidation.
5. Second oxidation for 10–12 hours in a vacuum environment. Formation of GABA: the tea leaves are stored in nitrogen in a stainless steel vacuum drum.
6. Heated in an oven for about 8 minutes to stop the fermentation of the leaves (the kill-green process). The heat (78°C) completely stops the oxidation/fermentation.
7. The leaves are now rolled in a ball rolling machine for about 2 minutes. The leaves are broken up by a rotating ball, causing the cell fluid to flow out, which spreads onto the surface and gives the tea a special aroma.
8. The leaves are then pressed, rolled, formed into a ball shape and dried in a cloth bag clamped into a rotating bottom plate in a canvas ball rolling machine.
9. Finally, the tea is dried in an oven at 80°C until the humidity level falls below 3%. The cloth ball rolling and drying process are then repeated several times over 10 hours.
This tea is not specifically roasted in any step; it gets its slight roasted notes in the last phase of drying by increasing the temperature to about 90°C.
Anaerobic storage of the harvested tea leaves converts the amino acids glutamine and asparagine into the amino acid GABA. This results in a GABA content up to 50 times higher than in conventional teas. The tea then goes through a special processing, fermentation and drying process.