Processing can affect the quality of tea in many ways. Many people know that green tea, oolong tea and black tea come from the same plant, camellia sinensis, just processed differently, but this talk focuses primarily on green tea.
Green Tea Processing
Basic green tea processing goes through following steps.
Heating (De-emzyme) -> Rolling -> Drying
These steps are slightly or greatly modified depending on regional variations and types of green tea processing to reach the end product. For example, longjin or dragon well is pan-fired and shaped into flat leaf while sencha is steamed and rolled into needle shape.
De-emzyme - Initial heating process
By heating the green leaf, enzyme present in tea leaf becomes dysfunctional. Emzyme is responsible for oxidation of tea leaf which causes tea leaf to turn black. Duration of oxidation determines which types of oolong or black tea you end up with. For green tea you do not want any oxidation so you stop oxidation at very early stage (or kill the green).
Initial heating process is very crucial in setting aroma in green tea. Too little heating can create uneven heating thus partially oxidized leaves while too much heating will lose the fresh green aroma and occasionally add burned taste to your tea. It is this subtle balance of initial heating that creates excellent aroma.
How can you tell? It takes a bit of experience, but once you know how it should taste, then it is easier to detect the bad ones.
Rolling of tea leaf allows tea to gain deeper flavor. Although it sounds simple to roll the leaf, but it takes back breaking hard work. Knowing the exact timing of rolling and softness of the leaf requires some experience. Rolling also evenly distribute moisture content of the leaf and prevents premature partial drying of tea leaf which generally leads to burns and powders.
Drying tea leaf is much more complex than just removing moisture out of leaf. It has different moisture levels at different areas of tea leaf and drying process has to remove the moisture evenly from the leaves. Uneven drying generally causes tea to taste like old rug or not fresh tasting.
Further understanding green tea processing gives me more room to experiment how to improve our green tea processing and also to learn the unique characteristics of tea in types of harvest, weather conditions, tea varieties, and even in what goes in the soil.