Rubbing and twisting is a type of tea making process, which is involved in most tea production processes. Rubbing and twisting can be understood as two actions: one is to knead and knead the tea leaves into strips, while the other is to twist and twist, which can break the tea cells, squeeze out the tea juice, and make the tea juice adhere to the surface of the tea strips, increasing viscosity and facilitating the formation of the shape of the tea leaves. This method reduces the area of the tea leaves and rolls them into strips.
The function of Tea leaf rolling
The function of rolling is not only to shape, but also to cause cell breakage and tea juice overflow. The overflowing tea juice adheres to the surface of the formed leaves, and only after drying can it be brewed to produce color and flavor. So rolling and twisting is a necessary processing step for making all kinds of tea (except for white tea).
The function of rolling is to shape the tea leaves into strips and to break down the cells in the tea leaves, causing the tea juice to overflow and adhere to the surface of the tea leaves, which is beneficial for increasing the concentration of the tea soup. This is also the reason why washing tea leaves quickly produces soup. The heavier the tea leaves are rolled and twisted, the less durable the tea leaves become
Common rolling and twisting methods
There are two common methods for rolling and twisting operations: manual rolling and mechanical rolling. At present, except for some famous tea processing that still retains a small amount of manual rolling, the vast majority of them have achieved mechanized operations.
(1) Hand rolling: Hand rolling is suitable for rolling small amounts of green tea or some other famous teas. Hand kneading is carried out on a kneading table. During the operation, hold the tea leaves in the palm of your hand with one or both hands, push and knead the tea balls forward on the kneading strips, and flip them in the palm of your hand. When the tea balls are kneaded to a certain extent, break them once to prevent the processed leaves from clumping.
(2) Mechanical rolling: Mechanical rolling is carried out using a tea rolling machine. When mechanically kneading, it is required to have an appropriate amount of leaves inside the machine, with “more tender leaves added and less old leaves added”. The pressure should be “light, heavy, and light”, and “tender leaves should be kneaded lightly in cold” and “old leaves should be kneaded heavily in hot”. Especially for some famous green tea processing, it is necessary to “lightly press and knead”.
Nowadays, tea leaves are often kneaded using a kneading machine. When tea leaves are put into a kneading bucket, they are subjected to multiple forces. Generally, machine kneading takes 20 to 30 minutes, and the more tea leaves in the kneading bucket, the more time is required.
Rolling can be divided into cold rolling and hot rolling. Cold rolling refers to the process of spreading green leaves for a period of time before rolling them. It is generally used for tender tea leaves because they have low cellulose content and high pectin content, making them easy to form during rolling;
Old leaves should be rolled while they are hot. Old leaves contain a lot of starch and sugar, and rolling while they are hot is beneficial for starch to continue gelatinization and for increasing the viscosity of leaf surface substances. Old leaves contain more cellulose, and hot rolling can soften the cellulose and make it easier to form strips. The disadvantage of hot kneading is that it is easy for the leaves to turn yellow and the water to become stagnant.
The requirement for kneading is to start with light and then heavy, gradually apply pressure, alternate between light and heavy, and finally not apply pressure. At the beginning, no pressure is applied to roll the tea leaves into strips along their veins, and then pressure is applied to break the cells.
The degree of rolling and twisting requires that the leaf forming rate of grade three or above should reach 80%, and that of grade three or below should reach 60%. The cell destruction rate of rolled and twisted leaves should reach 45% -55%, and the tea juice should adhere to the surface of the tea leaves, giving a moist feeling when touched by hand.