Simply put - the Oolong Tea (Wulong) is a semi-oxidized tea leaf.
From a processing standpoint oolongs (Chinese - black dragons) - are somewhere between green and black tea. Oolong is the most labor intensive of the types of tea, and the most highly prized oolongs are processed only by very experienced tea masters. The specific varietals of the Camellia Sinensis (tea plant) used in traditional oolong teas come from Fujian and Guangdong provinces in mainland China, and largely from Taiwan.
Simplified description of processing of oolongs comprises of the following steps:
Tea leaves are picked and withered about like green teas that makes fresh tea leaves flaccid and pliable.
2. Bruising/Shaking & Oxidation:
After withering, the tea leaves are rolled or shaken to bruise the edges of the leaves and to release some of the enzymes – peroxidase and polyphenol oxidase in the leaves. The release of the enzymes triggers the oxidation process. When polyphenols mix with enzymes and are exposed to oxygen they begin to turn brown in color, much like when an apple is cut open and the flesh begins to turn brown when exposed to the air. This process of oxidation in oolongs is what really brings out their unique flavors and requires the experience of the tea masters to judge when the teas are actually ready. A complex process of further rolling or shaking along with slow and low temperature drying steps takes place until the tea master decides that the tea has oxidized to the point that tea master deems appropriate to the style being produced.