Green tea is steamed primarily to halt oxidation and preserve its characteristic flavor and color.
The "Kill Green" Process
The steaming process, sometimes referred to as "kill green" by tea producers, is crucial for Japanese green teas. It involves applying heat to the freshly picked tea leaves within hours of harvesting. This step achieves the following:
- Stops Oxidation: Steaming inactivates the enzymes responsible for oxidation, the process that turns tea leaves brown and alters their flavor.
- Inactivates Enzymes: By deactivating these enzymes, the natural chemical reactions within the leaf are stopped, preventing decay and undesirable changes.
- Preserves Flavor: Locking in the desired flavors of the tea leaf.
- Maintains Color: Steaming helps retain the vibrant green color that is characteristic of green tea.
Essentially, steaming ensures that green tea retains its fresh, vegetal flavors and bright color, rather than developing the darker, more oxidized flavors found in black or oolong teas. Different methods of heat application exist (such as pan-firing in Chinese green teas), but steaming is a common and effective method, particularly in Japanese green tea production.
