Kneading is a process in the production of Pu'er Tea after the fresh leaves have been subjected to initial fixation. It involves using external force to shape the tea leaves into strips and breaking down the cellular structure of the fresh leaves, allowing the internal substances of the tea to adhere to the surface of the leaves.
The significance of this process lies in rupturing cell walls to release tea juice, facilitating the polymerization of components such as polyphenols and catechins, preparing the tea for later fermentation, and curling loose tea leaves into strips, which helps with the even release of internal substances during brewing. The strength of kneading, duration, and cell breakage rate are closely related to the taste, aroma, and subsequent transformation of Pu'er tea.
Cold Kneading vs. Hot Kneading
The principle of kneading is to use hot kneading for older leaves and cold kneading for younger leaves, as well as heavy kneading for older leaves and gentle kneading for younger ones. Based on personal experience in tea production, Pu'er tea requires heavy kneading, which is not done in one go but rather through repeated kneading. The purpose of “repeated kneading” is essentially to supplement the first “natural inoculation,” ensuring that the initial oxidation of Pu'er tea is completed more thoroughly.
Tea that has undergone hot kneading produces a murky Infusion, with a yellow-green color and a dry sensation in the mouth, and the texture of the liquid is slightly coarse. The infusion colors produced by the two methods of kneading are completely different. Cold-kneaded tea produces a clear infusion, also yellow-green in color, with an aromatic presence upon entry into the mouth and an extremely fine texture.
The Impact of Kneading Strength on Tea Quality
During the kneading process, if the kneading is relatively light, the damage to the surface tissue of the leaves is minimal, and fewer internal substances are released. This results in sun-dried raw tea with relatively loose and less compact strips. When used to produce finished Pu'er tea, the new tea will have a slower infusion time during brewing, and its durability when steeped will be longer. In long-term storage, due to the relatively loose strips, the internal space of the finished tea will have better ventilation, leading to faster aging.
If the kneading is relatively heavy, there is greater damage to the surface tissue of the leaves, and more internal substances are released. This results in sun-dried raw tea with tighter strips. When used to produce finished Pu'er tea, the new tea will require quicker infusion times for the first few steeps and will have poorer durability when steeped. During long-term storage, due to the tighter strips, the aging process of the finished tea will be slower and less pronounced. Additionally, excessive kneading during the process can cause the veins of some tender leaves to break, resulting in poor integrity of the Leaf base.
Differences Between Hand Kneading and Machine Kneading
Hand kneading of Pu'er tea typically involves two rounds of kneading. The initial kneading takes place after the tea leaves have been fixed and spread out to cool, and the leaves are kneaded until they form basic strips and tea juice seeps out. The leaves are then left to air until the next morning, followed by a second round of kneading to ensure that even the coarser and older stems and leaves are tightly formed into strips. A specialized Bamboo mat is used for hand kneading. The technique requires circular, complete, and coordinated movements that are both firm and gentle, ensuring that the tea leaves are evenly pressured, aiding in strip formation.
Using a kneading machine for kneading is now the most commonly chosen method in Pu'er tea production areas. The cell breakage rate during kneading is between 45-60%. The extent of kneading depends on the tenderness of the raw materials and the desired outcome of the tea, controlled through pressure and kneading time. Depending on the diameter of the kneading drum, the amount of leaves added should be adjusted. If too few leaves are added, the pressure applied during kneading will have little effect, making it difficult to form tight strips; if too many leaves are added, the force will be unevenly distributed, and the initial flipping and turning of the leaves will be obstructed, leading to poor initial curling. Often, the result is a loose and broken appearance, with more fragments at the bottom and flatter strips at the top, ultimately producing a loose and broken appearance. A reasonable amount of leaves to add is to naturally fill the kneading drum with the fixed leaves.
Kneading is an important step in the production of Pu'er tea, affecting not only the appearance of the strips but also playing a crucial role in the subsequent oxidation process.