Manufacture of Oolong Tea
Almost exclusively produced in China and Formosa (Taiwan), Oolong teas fall between the unfermented green teas and the fully fermented black teas. They are processed to be full-bodied teas and are therefore made from larger, more mature leaves.
Immediately upon plucking, the leaves are spread out in direct sunlight to wither. Withering reduces the moisture content and softens the leaves. The leaves are then put into bamboo baskets and shaken briskly to bruise the leaf edges. In the next step, the leaves are spread out in the shade to dry. The process of shaking and spreading of the leaves is repeated numerous times. The bruised leaf edges begin to turn red through the oxidation process (fermentation) while the centers of the leaves remain green.
The amount of fermentation depends on the type of Oolong and can vary from approximately 20% for a "green" oolong, to 60 % for a classic Formosa oolong. Once the desired level of fermentation is reached, the process must be stopped immediately. This is done by pan-firing the leaves at high temperatures, which produces lower moisture content than is found in green tea, and ensures a longer shelf life for Oolongs.