pu'er tea dark tea liu bao cha

Oolong tea is a traditional Chinese tea. It’s made from the same plant used in black and green teas, but the leaves are processed differently.

This tea-making process is called oxidation. Exposing the tea leaves to air causes them to ferment, and the length of time a tea maker allows the leaves to oxidize impacts the tea’s color, flavor, and to an extent, its nutritional content. 

Green tea is unoxidized, which helps it retain some plant-based antioxidants like catechins, which would be lost or converted during oxidation. Black tea is fully oxidized, giving it a deeper, richer flavor. This fermentation process also forms nutrients called theaflavins, powerful antioxidants unique to oxidized teas.