Kneading is one of the important processing techniques that shapes the attractive appearance and enhances the quality of Tea. The effectiveness of kneading depends on the physical properties of fresh tea leaves and the kneading technique used. In actual production, experienced masters will reasonably select kneading techniques based on the physical properties of the fresh tea leaves (such as moisture content, Leaf temperature, etc.) to ensure the production of products with both excellent appearance and internal quality.

    What factors influence the quality of tea kneading in actual tea production?

    1. Kneading Method
    Kneading methods include hand-kneading for some high-quality teas and mechanical kneading for most others. The amount of leaves loaded into the machine varies depending on the size of the kneading drum, ranging from 10kg to 50kg, which is dozens to hundreds of times more than hand-kneading. As a result, mechanical kneading is far more efficient than hand-kneading.
    Xiangyuan Qihong's intangible cultural heritage technician “Old Xie” kneading tea
    It is worth mentioning that Black Tea can be divided into black leaf tea and black broken tea based on its manufacturing method and finished product appearance. Therefore, there are differences in traditional methods, CTC (Crush, Tear, and Curl), and LTP (Laurie Tea Processor, a method that uses a Laurie-style hammer machine to crush tea leaves). These processing methods can result in varying degrees of cell damage, producing teas of different qualities. Traditional kneading is suitable for black leaf tea (such as Qimen black tea), where fewer cells are damaged. Black broken tea often uses CTC and LTP methods, resulting in more complete cell damage and allowing catechins to be oxidized more evenly and effectively by polyphenol oxidase. Research has shown that using the CTC method increases the content of theaflavins and thearubigins in black tea, meeting the requirements for a “strong and fresh” liquor. However, traditionally processed teas have better aromatic characteristics than those processed using the CTC method, so traditional methods can produce teas with better aroma.

    2. Leaf Loading Amount
    The leaf loading amount primarily depends on the type of kneading machine and the tenderness of the fresh leaves. Soft tender leaves with less elasticity are easier to knead into shape, while hard coarser fresh leaves with more elasticity are not as easily shaped. Therefore, more tender fresh leaves can have a higher loading amount, while coarser ones should have a lower loading amount.
    Various kneading machines have specific appropriate ranges for leaf loading amounts. If the loading amount is too small, it can reduce the effect of pressure during kneading, making it difficult to tightly form the tea strips. If the loading amount is too large, the leaves' movement within the kneading drum is impeded, leading to uneven kneading. Often, this results in more fragments and dust at the bottom and more flattened strips at the top, which is one of the main reasons for loose, flattened, and broken defects in the tea's appearance.

    3. Kneading Time
    During the kneading process, kneading time significantly affects the quality of the kneaded leaves. Kneading time should be determined based on the age of the raw material and the degree of withering (or fixation). If the time is too short, the strips will not be tight, there will be more coarse strips and fewer fragments, and the brewed tea will be light. If the time is too long, although it reduces the number of coarse strips, there will be more breakage, leaf tip fractures, and fragments, and the appearance will be irregular.
    Different types of tea have different kneading requirements. Green Tea requires durability in brewing, so the kneading time should not be long, and the pressure should be light, balancing the shape and quality of the product. Black broken tea, on the other hand, emphasizes the strength and intensity of the liquor, so kneading should be strong and quick, meaning the pressure should be high and the kneading time short.

    4. Kneading Pressure
    Pressure application during kneading is a core element of kneading technology. The weight and duration of the pressure greatly affect the tightness, flatness, and fragmentation of the tea strips. The extent of kneading also significantly impacts the damage rate of the leaf tissue and the color, aroma, and taste of the internal quality. High pressure produces tightly bound strips, but excessive pressure can cause the strips to clump together and break easily, resulting in unsatisfactory liquor color and flavor. Insufficient pressure causes the strips to be coarse and loose, or even fails to achieve the purpose of kneading.
    The principle of pressure application throughout the kneading process should be “light → heavy → light.” No pressure is applied at the beginning of kneading. Once the leaves start to curl into strips, pressure is gradually increased, followed by alternating periods of increased and reduced pressure. Tender leaves require light pressure and shorter kneading times, while older leaves need heavier pressure and longer kneading times. For black tea, which requires more thorough kneading, the pressure should be greater and the kneading time longer.

    5. Temperature and Humidity of the Kneading Room
    For black tea, enzymatic oxidation begins with kneading. The heat generated by oxidation raises the temperature of the leaves in the kneading drum, further increased by the friction during kneading. If the room temperature is too high, the heat cannot dissipate into the surrounding space, causing an accumulation of heat and an increase in leaf temperature, which intensifies the oxidation process. Under poor oxygen supply conditions within the kneading drum, fermentation cannot proceed normally, affecting the quality of the tea. Therefore, the kneading room should be relatively cool. Generally, the room temperature should be controlled between 20-24°C. If the room temperature is high, measures such as increasing humidity and cooling should be taken, such as sprinkling water or misting in the room.
    At the same time, fermentation inevitably occurs during kneading. If the relative humidity in the air is low, the moisture in the kneaded leaves evaporates easily, which is detrimental to fermentation. Therefore, the kneading room should maintain a high relative humidity, typically around 85-90%.
    Unclumping and sieving is a necessary step for most teas after kneading. After kneading, the tea leaves tend to clump together, sometimes as large as a fist and sometimes as small as a walnut. An unclumping machine is needed to separate the clumped tea strips, sieve out the fine leaves and fragments, and improve the quality of the raw tea.