As tea is picked from tea trees, it undergoes withering, fermentation, rolling, drying etc, and then when brewed in hot water, tea is made. In this process, one of the key processes is fermentation. Fermentation allows tea to undergo both biological and chemical reactions, which defines the flavor of teas we are familiar with.
In brief, fermentation occurs when Catechin oxidizes, and with the help of tea polyphenol, caffeine and L-Theanine and the tea masters’ experience, different types of fermentation processes and teas are made. Teas can be generally categorized as follows:
Green Tea：Non-fermented
Tea Polyphenols─Astringency ☆☆☆☆☆
Caffeine─Bitterness ☆☆☆☆☆
L-Theanine─Sweetness ☆☆☆
To avoid fermentation, after the teas have been picked, fixation occurs. In Taiwan, a lot of people use woks to mix the teas. Since it doesn’t undergo fermentation, the tea itself and its substances will directly affect the taste of tea. There aren’t that many green tea plantations in Taiwan. Some specialties include Longjing tea and biluochun.
Oolong Tea：Partly-fermented
Tea Polyphenols─Astringency ☆☆☆
Caffeine─Bitterness ☆☆☆
L-Theanine─Sweetness ☆☆☆☆☆
Oolong tea is one of the most popular and rich type of tea in Taiwan, and the roasting technique is especially important. Depending on the degree of roasting, the color will reflect on the tea; the darker it is, the heavier the roast. Main types of oolong include Oolong, Pouchong Tea, Tieguanyin, Oriental Beauty Tea.
Black Tea：Completely Fermented
Tea Polyphenols─Astringency ☆☆☆
Caffeine─Bitterness ☆☆☆
L-Theanine─Sweetness ☆☆☆☆☆
Since black tea is completely fermented, it has a radiant red color and a strong taste. The color is also darker than most teas and may seem more astringent. Some of the well-known black teas include Ridong Black Tea, Sun Moon Lake Black Tea, Taicha No.18, Assam Black Tea and Darjeeling Black Tea.
Pu’er Tea：Post-Fermentation
Tea Polyphenols ☆☆
Caffeine─Bitterness ☆
L-Theanine─Sweetness ☆☆☆☆☆
Also known as “Dark Tea”. After fixation and rolling, the tea starts oxidizing under a warm and wet environment. This is a non-enzyme fermentation, therefore “aging” becomes the key characteristic.
The description above gives you an overview of the different types of fermentation processes of different kinds of teas. Each type of tea will taste different due to its fermentation process, from the light green tea that is non-fermented to the dark black tea that is completely fermented. Please take note of these different characteristics when you taste the different teas. That way you will be able to distinguish between the good and bad teas.