Japanese green tea called sencha typically come from first and second harvest leaves. Unlike shaded teas such as matcha, kabusecha, and gyokuro, sencha is grown under full sunlight year-round. Because of this, sencha contains a high level of vitamin C, catechins and is generally lower in L-theanine compared to shaded teas. However, despite this, sencha contains some of the highest levels of L-theanine among all non-shaded Japanese teas and especially compared to black teas or other types of green teas.
Once the leaves have been harvested, they go through a steaming process. This is essential in this type of green tea production because it stops the oxidative enzymes. Without this process the leaves would oxidize and become oolong or black tea.
There are three steaming levels based on the duration of the steaming process: