1. Immobilization: Immobilization is the most important step in the processing of green tea and plays a decisive role in the quality of green tea. Immobilization is to destroy the activity of enzymes in tea by high temperature, and to prevent the possibility of tea from continuing oxidation. From the appearance, the leaves have not turned red. At the same time, the moisture in the leaves is evaporated, which makes the leaves soft and prepares for kneading. Iron pot killing should master the principle of "combining shock with boredom, more earthquakes and less boredom" Shake is to hold the leaves high, which is conducive to the loss of water, the volatilization of grass gas, the fragrance of leaves, and prevent the leaves from turning yellow. Moistening leaves is to cover the leaves without lifting them, so that the residence time of hot steam in the leaves is short, the temperature of leaves is rapidly increased, the activity of enzymes is completely destroyed, the hydrolysis and transformation of related substances are promoted, the buds and leaves are killed evenly and thoroughly, and the production of red stems and red leaves is avoided.

2. In this step, with the increase of temperature, water evaporates, low-boiling aromatic substances in tea volatilize, high-boiling aromatic substances are exposed, and the aroma of tea will also increase. Generally, the temperature of iron pan is required to be between 260-320℃, which is easy to fry if it is too high, and will destroy the activity of enzyme if it is too low. Generally, the water-setting time of iron pot is 5- 10 minutes, and the water-setting time needs to be extended if the amount of tea is large. If the time is too long, the tea leaves will lose too much water, which is not conducive to kneading.

3. Kneading: Kneading is a process of shaping the shape of green tea. Under the action of external force, the leaves are crushed and lightened, rolled into strips, and the volume is reduced, which is convenient for brewing. At the same time, tea juice overflows and adheres to the surface of leaves, which also plays an important role in improving the taste concentration of tea. The rolling process of making green tea can be divided into cold rolling and hot rolling. The so-called cold kneading is to spread the green leaves and roll them up; Hot rolling is to roll the leaves while they are still hot, and don't scatter them. The tender leaves should be cold-kneaded to keep the bright yellow-green soup color at the bottom of the tender green leaves, and the old leaves should be hot-kneaded to facilitate close knot and reduce fragments. Green tea is generally rubbed once, and young leaves generally need to be rubbed for 20-25 minutes. Old leaves are rubbed under heavy pressure for a long time, screened in blocks and rubbed several times, but the total time is generally less than 50 minutes. The rate of high-grade tea strips is above 85%, and the cell breakage rate is above 45%. The peeling rate of low-grade green tea is above 60%, and the cell breakage rate is above 65, which is a sign of the completion of kneading.

4. Drying: Drying plays a role in shaping tea, fixing tea quality and developing tea fragrance. There are three drying methods: sun drying, frying and drying. In the drying process of green tea, it is usually dried first and then fried. Because the water content of the twisted tea leaves is still very high, if fried directly, lumps will quickly form in the pot of the frying machine, and the tea juice will easily stick to the pot wall. Therefore, tea leaves should be dried first to reduce the water content to meet the requirements of pot frying.

5. Withering: Withering refers to the process that fresh leaves lose water for a period of time, causing some hard and brittle stems to wither and wither. This is the first process of black tea preliminary production. After withering, the water can be properly evaporated, and the leaves are soft, the toughness is enhanced, and the shape is convenient. In addition, this process is an important processing stage to form the aroma of black tea, which makes the grass fragrance disappear and the tea fragrance appear. There are two ways of withering: natural withering and trough withering. Natural withering is to spread the tea thinly indoors or outdoors where the sun is not too strong, and leave it for a certain time. Withering trough withering is to put fresh leaves in a ventilation trough and introduce hot air to speed up the withering process, which is a common withering method at present.

6. Fermentation: Fermentation is a unique stage in the production of black tea. After fermentation, the color of leaves changed from green to red, forming the quality characteristics of black tea, red leaves and red soup. The mechanism is that the cell membrane structure of tissues is destroyed under the action of leaf rolling, and the permeability is increased, so that polyphenols are fully contacted with oxidase, and oxidative polymerization occurs under the action of enzyme, and other chemical components also undergo profound changes accordingly, which makes green tea turn red and forms the color, fragrance and quality of black tea. At present, fermentation machines are widely used to control the temperature and time of fermentation. Moderate fermentation, the color of young leaves is red and uniform, the old leaves are red and blue, the smell of grass disappears, and there is the fragrance of mature fruits.

7. Drying: Drying is the process of baking the fermented tea blank at high temperature, quickly evaporating water and achieving quality drying. It has three purposes: using high temperature to quickly inactivate the activity of enzyme to stop fermentation; Evaporate water, reduce volume, fix appearance, keep dry and prevent mildew; Emit most of the low-boiling grass fragrance, strengthen the retention of high-boiling aromatic substances, and obtain the unique sweetness of black tea.