Main Types
There are three main types of tea: green tea, black tea and oolong tea. Each type of tea is named after a certain colour, which is the result of the processing method involved. While green tea is unfermented, black tea is fermented and oolong tea is semifermented. The different degrees of fermentation result in every type having its own taste, appearance and nutritional components.
Green Tea
Green tea is unfermented, meaning that the leaves are not allowed to brown. When the green tea leaves are picked, they begin turning brown through a process called oxidization. In order to stop this process from occuring, the freshly-picked leaves are steamed immediately. Steam deactivates the oxidizing enzymes, “freezing” the leaves and keeping it from browning. When steaming is complete, the leaves are then rolled into thin needle shapes and left to dry. Rolling helps to seal in the nutritional components in the leaf, such as vitamin C. This is one of the main reasons why green tea is considered better for health as compared to black tea or oolong tea.
Black Tea
Black tea is fermented – the tea leaves are significantly browned. Unlike green tea where oxidization is minimised, black tea is allowed to go through the natural process of oxidization. The freshly-picked tea leaves are first withered, either by leaving to dry in the warmth of sunlight or by pumping unheated air through a layer of the leaves. They are then rolled to break up the cell walls on the leaf’s surface. Broken cell walls allow more effective oxidization of the leaf. At this juncture, you would be able to pick up the distinct aroma and dark color of black tea. When the leaves have sufficiently been oxidized, they are heated in iron pans and dried to prevent further oxidation. The leaves are finally rolled to ensure better infusion when brewed with hot water.
Oolong Tea
As oolong tea is semifermented, you might say it is part-green tea, part-black tea. Like black tea, the freshly picked tea leaves are allowed to “wither” in the sun and indoors to reduce moisture content. However, when the leaves become about 30 percent oxidized, they are heated in an iron pan to prevent any further oxidization, much like how green tea is made.
Nutritional Benefits
As oxidization destroys vitamin C, allowing leaves to wither/oxidize for different spans of time will give you leaves with varying amounts of vitamin C content. Green tea, having virtually no exposure to oxidization, retains nearly all its vitamin C content. Black tea, however, virtually has none. Of course, oolong tea typically has mid-range amounts.