The method of processing green teas involves heating, rolling and drying. Step one, the heating, is most important. Heating the fresh leaves results in the inactivity of enzymes. The chemicals in the leaves go through chemical and physical reactions by thermodynamic force without the impact of the enzymes.
Heating determines the quality of green tea. Through heat, the enzymes are destroyed, and the polyphenols are prevented from being oxidized. Heating tealeaves properly will prevent some of the water in the leaves to evaporate and makes the leaves soft. This prepares the tea for rolling. After the water evaporates, the aromatic substances with grassy odor and low boiling points will volatilize, and the odor of green tea is improved. Factors influencing the quality of heating include temperature, dosage, heating machines, time, and methods. They are related with each other.
The heat neutralizes active oxidize, which oxidizes tea polyphenols, and helps preserve chlorophyll to keep green color in the leaves. What’s more, the high temperature used results in high evaporation and softens the leaves, which helps rolling tea eaves in shape. Heating also removes some unwanted scents, and enhances the flavor of the tea.
Steaming and stirring are two common heating techniques. The first one uses hot steam to heat the leaves. It’s fast and convenient, and commonly used in flow lines. Stirring is conducted in a hot wok and the workers keep stirring the leaves by hand until the leaves change color. The best handmade tea is usually stir fixated. Stir fixation is complicated because one small mistake will ruin the whole batch.
Tealeaf workers almost always rely on their senses when doing this process, which requires years of practice, and an experienced worker is highly needed. Throughout this process, the leaves should turn dark green, and unpleasant scents should disappear and amour should remain strong. The leaves should be neither too hard nor too soft, and don’t break when squeezed. Why is this? The damp leaves are easier to roll into wrinkled strips. Thousands of years ago, Chinese tea makers introduced the rolling technique to tea manufacturing because it helped shape the leaves into a smaller form factor.
In the 12th century, heating tealeaves through stirring was invented, and many traditional tea workshops are still using it to this day. Since tea processing became an industry, techniques and methods are always changing and developing. Different workshops create their unique techniques according to environmental varieties.
Next is rolling. Rolling is the procedure of shaping the green tea. The leaves break down, and are shaped curly and twisted by external forces. Moreover, tea liquor squeezed onto the surface of leaves significantly enhances the density of flavor and is often used for more high-end teas.
The rolling procedure is categorized as “Cold rolling” and “Hot rolling”. Cold rolling refers to the rolling after the leaves cool down following the heating. “Hot rolling” refers to the rolling before the leaves cool down after the heating. Cold rolling is more suitable for fresh leaves, because it produces light golden and yellowish green colors at the bottom of leaves. Hot rolling is more suitable for old leaves, because it makes the rolls compact with fewer minced parts. Nowadays, rolling green tea leaves is done by machinery, except by a few kind of hand-made well-known tea.
Lastly, the tea needs to be dried. The purpose of drying is to vaporize the water, shape the tea and to produce the tea flavor and odor.
The ways of drying include oven-drying, pan-drying and sun-drying. The order of the procedure of drying green tea leaves is always oven-drying followed by pan-drying. The green tea leaves still have a high moisture level after rolling. The leaves will turn into bulk and sticks to the bottom of the pan if the doing pan-firing first. So oven-firing goes first, and the moisture level will decrease to meet the requirement of pan-drying.
Drying is the last step before selling. According to different local environment and tea spices, tea workers select myriad ways, including baking, frying, air drying, and sunning. In the handmade process, the leaves are baked before frying. Damp leaves can stick to each other while frying.
In tea factories, baking is the most common. Great care must be taken in order to not over-cook the leaves or it can ruin the flavor.
Fujian province, one of the main tea producing areas in China, is leading the technology revolution within the tea industry. For example, because of air pollution, many factories use air condition drying instead of sunning. Moist tealeaves are spread in drying rooms with fixed temperatures and humidity.
Green tea is the oldest tea in the world, according to various historical records. 3,000 years ago, the Chinese ancestors started to collect some leaves and sunned them. Technically, green tea drank and sold in a market context was invented in the 8th century, when steaming techniques were widely used.
There is a debate on whether modern techniques should be applied to the tea industry. Different people hold different opinions. Some believe only the classic methods can produce the best green tea. Some think machines and modern technique can improve the efficiency and aren’t against the traditions. Whatever the case may be, we believe as long as the teas are at least organic and health benefiting, beginner tea drinkers should focus on this and as their palette expands look more into high-end teas with specific heating and preparation methods in order to enjoy green tea even more.