The Green Tea Fermentation Process

Plucking the Leaves

The green tea fermentation actually begins as soon as the Camellia sinensis leaves are plucked. This is because tea leaves start to brown, wilt and oxidize once they have been picked as its necessary chlorophyll diminishes and the tea leaves release their tannins. Once the leaves are picked they are dried to slow down the wilting and oxidizing process. Afterward they are sorted and cleaned, ensuring that only the smallest, highest quality leaves are utilized in the tea.

Enzymatic Oxidation

The process of fermenting tea is actually called enzymatic oxidation, as it is an aerobic process, meaning that the leaves require air in order to "ferment." Though some tea leaves are allowed to oxidize for various periods of time, green tea leaves must be completely prevented from oxidizing, meaning that they must be fermented, or heated, quickly. The heating process essentially shuts down the tea leaves' enzymes, which prevents them from oxidizing and releasing their chlorophyll.

Heating Process

There are five main ways that green tea is heated, including microwaving, pan frying, steaming, roasting and firing. Leaves should be microwaved for approximately two minutes, while pan-fried leaves, according to the University of Hawaii's College of Tropical Agriculture and Human Resources, should be placed in a wok and cooked over low heat for about a minute and a half. Steaming should take between 20 seconds and two minutes, depending on the desired taste and aroma. The longer the steaming the more pungent the tea. The same holds true for the roasting and firing processes. Once the green tea leaves have been properly dried and heated they undergo a secondary drying process. The leaves are spread out onto an oven tray and cooked one final time to remove the leaves' lingering moisture. This is usually done in a conventional oven. Though oven times may vary, the leaves are typically cooked for one hour at 140 degrees.