Steaming

Steaming is the process of heating freshly picked tea leaves with steam to stop the action of oxidative enzymes. In matcha production, it is an early step that helps prevent unwanted browning and excessive grassy notes before the leaves move on toward tencha.

The role of steaming

After harvesting, fresh tea leaves begin to oxidize, which changes their color and aroma. Steaming stops this change quickly. Whether the tea will later be rolled or, as with tencha, dried without rolling, this first heating step helps set the direction of the finished tea.

Steaming is different from firing and drying. Steaming is done to fresh leaves to deactivate enzymes. Firing is a later heat treatment used to adjust moisture and aroma, while drying reduces moisture for storage and further processing. It also differs from pan-firing, which uses a heated pan rather than steam.

In the matcha process, steamed leaves are cooled and then dried without rolling. One type of equipment used for this drying stage is the tencha-ro. The leaves are then refined into tencha by removing stems and veins, and finally milled into a fine powder. You can see the broader sequence in how matcha is made.

For drinkers, the degree of steaming is not usually something that can be judged on its own. More practical cues are the powder’s color, aroma, texture, and suitability for the intended use. After purchase, matcha is not steamed again; it should be protected from moisture and light and used reasonably soon after opening.