Management of Fresh Tea Leaves

Fresh leaves are the raw materials for tea production and the foundation of tea quality. Only high-quality fresh leaves can produce excellent tea leaves. If the management of fresh leaves is not strengthened during the picking, transportation, and storage process, it will cause damage to the fresh leaves, reduce their freshness, and thus bring certain economic losses. A correct understanding of the preservation principles of fresh leaves and the rational use of preservation techniques have important practical significance for guiding tea production.

Factors affecting the quality of fresh leaves after harvesting

After being picked and removed from the tea tree, the quality of fresh leaves is in a dynamic state, affected by factors such as moisture, temperature, air, and damage. The chemical composition of fresh leaves also changes to varying degrees, which has a certain impact on the quality of fresh leaves.

1. Fresh leaf moisture

With the continuous loss of moisture from fresh leaves, their contents undergo significant decomposition and oxidation, which can affect the quality of tea leaves. In severe cases, it can cause the fresh leaves to deteriorate and lose their economic value. Therefore, water retention is one of the important measures for fresh leaf preservation. Firstly, it can reduce the loss of dry matter, and secondly, it can prevent the phenomenon of leaf withering caused by excessive water loss of fresh leaves. In production practice, in order to achieve the purpose of keeping fresh leaves water and fresh, water spraying or spray is usually adopted to keep fresh storage places at a high humidity.

2. Temperature

The external temperature mainly affects the respiration of fresh leaves. Fresh leaves release a large amount of heat during respiration, causing a rapid increase in leaf temperature. The higher the external temperature, the stronger the respiration of fresh leaves, and the faster the leaf temperature rises. As a result, the enzyme activity of fresh leaves continues to increase, and a large amount of effective ingredients are decomposed or oxidized, which will have an adverse effect on the formation of tea quality. Therefore, during the process of picking, transporting, and storing fresh tea leaves, appropriate low temperatures will be beneficial for maintaining the freshness of the tea leaves.

3. Oxygen

During the picking, transportation, and storage of fresh leaves, if the accumulation is too thick and poorly ventilated, anaerobic respiration may occur. Although anaerobic respiration releases far less heat than aerobic respiration, poor ventilation hinders the diffusion of heat from the leaf pile, leading to a gradual increase in leaf temperature and enhanced enzyme activity, which accelerates the decomposition of organic matter and strengthens the oxidation of polyphenolic substances.

Studies have shown that within a certain period of time, the longer the fresh leaves are piled up, the higher the temperature, and the more dry matter is lost, resulting in a significant reduction in soluble polyphenols and water extracts. In addition, due to the accumulation of fresh leaves and lack of oxygen, monosaccharides in the body will decompose into ethanol, producing the odor of distiller’s grains. If the stacking time is further extended, the protein will gradually hydrolyze, causing an increase in ammonia nitrogen, and the fresh leaves will produce a foul odor or sour taste, which will have a negative impact on the aroma of the tea. Therefore, air circulation should be maintained during the picking, transportation, and storage of fresh leaves to prevent anaerobic respiration that may affect tea leaves

4. Mechanical damage

After mechanical damage to fresh leaves, on the one hand, it promotes enhanced respiration and rapid increase in leaf temperature; On the other hand, it leads to enzymatic oxidation of polyphenolic substances, which can easily cause leaf redness.

The significance of fresh leaf management

Sprouts and leaves grow on tea trees, relying on photosynthesis to produce sugars, and decomposing organic matter through respiration to release energy to maintain the life activities of tea trees. After the buds and leaves are harvested from the tea tree, their life activities continue for a certain period of time.

However, due to the continuous reduction of water and nutrients in the harvested fresh leaves, assimilation and differentiation have entered a state of disorder, and respiration continues to increase. With the rise of leaf temperature and the loss of water, fresh leaves gradually lose their original physical and chemical properties, undergo drastic changes in chemical composition, and increase the consumption of effective substances, leading to a development that is not conducive to the formation of tea quality. Therefore, fresh leaves should be harvested and processed on site in production.

However, during the peak period of large-scale production, it is difficult to achieve on-site harvesting and production of fresh leaves. Especially in southern tea regions or during summer, with high temperatures, improper storage of fresh leaves after harvesting can easily lead to a decline in their quality. In order to maintain the freshness and quality of fresh leaves, it is necessary to do a good job in fresh leaf management.