Japanese “green” tea
Tea can be broadly classified into unfermented tea, semi-fermented tea, and fermented tea, depending on the extent of oxidase function. To make unfermented tea, we should heat fresh leaves by roasting or steaming before the enzymes in leaves begins oxidation.
In Japan, where the fresh green taste of unfermented tea is favored, fresh leaves are steamed immediately after harvest (steamed green tea) to stop oxidation. By contrast, in China and in other regions of the world, most green tea is made by pan-roasting. Roasted green tea (Kamairicha, 釜炒り茶) is also made in some parts of Japan. Semi-fermented and fermented tea are not produced in large amounts today (less than 10%).
During the production of another variant of tea such as Pu’er tea in China, the tea leaves are literally fermented with lactic acid bacteria and yeast after heating (post-fermented tea). While this variant of tea is uncommon in Japan, some interesting local teas are produced in some regions.