Among the six major categories of tea, black tea, green tea, and oolong tea are the most common in Taiwan. People often try to tell them apart by their color, but that’s not always accurate. The real differences lie in their processing methods and oxidation levels. Let’s take a closer look at what makes these teas similar and how they differ.
Difference Between Black Tea, Green Tea, and Oolong Tea: Oxidation Levels
Green tea is an unoxidized tea, with an oxidation level typically below 5%. Oolong tea is a partially oxidized tea, with Taiwanese oolong ranging from 8% to 90%. Black tea is a fully oxidized tea, with levels ranging from 95% to nearly 100%.
Difference Between Black Tea, Green Tea, and Oolong Tea: Processing Methods
The processing steps for green tea are: harvesting, fixing (kill-green), rolling, and drying.
Notice that green tea leaves go straight to the fixing stage after harvest, skipping withering, tossing, and oxidation. This makes green tea essentially unoxidized (with only a tiny amount of natural oxidation happening between picking and fixing).
The production process of Oolong tea follows this order: Plucking, Withering, Tethering/Tossing (Langqing), Fixation, Rolling, and Drying.
Oolong tea goes through withering and tossing, both of which allow the tea leaves to ferment. The degree of fermentation depends on the specific type of Oolong tea being made. Among Taiwan’s Oolong teas, Pouchong and High Mountain Oolongs have the lightest fermentation at 9% to 25%, while Red Oolong and Oriental Beauty have the heaviest fermentation, approaching 90%.
The production process of black tea is: Plucking, Withering, Rolling, Fermentation, and Drying.
The biggest difference between black tea, Oolong tea, and green tea lies in the fact that the processing method skips the fixation step (the purpose of fixation is to deactivate the enzymes in the tea leaves, thereby stopping fermentation). Instead, the leaves are rolled directly after withering and allowed to continue fermenting. As a result, black tea has the highest degree of fermentation, reaching over 95% and close to 100%.
Why you shouldn't distinguish tea by the color of the brewed tea and leaves
Because Oolong tea varies widely in its degree of fermentation, the color differences are also substantial. For example, Pouchong, which has the lightest fermentation, is similar in color to green tea. Oriental Beauty, which has the heaviest fermentation, is quite similar in color to black tea. It is truly difficult to tell them apart simply by their appearance.
Differences in processing methods between black tea, green tea, and Oolong tea
Simply put, green tea is not fermented and goes straight to fixation; black tea skips fixation and continues to ferment; and Oolong tea involves both steps.