Journal of Tea Science Research, 2024, Vol.14, No.1, 1-9 http://hortherbpublisher.com/index.php/jtsr 4 leaves are influenced by factors such as tea cultivars, growing environment, and processing techniques. Research has shown that the presence of endophytic microorganisms in tea leaves can affect the chemical composition and flavor characteristics of tea leaves. In addition, during the production of tea, microorganisms in the air may also have an impact on the tea. Microorganisms in the air can enter the tea garden and tea processing environment through wind and other ways, and come into contact with tea. These microorganisms have certain effects on the fermentation process, storage and quality of tea. The diversity and function of tea microorganisms play an important role in the growth, processing and quality formation of tea. Understanding the characteristics and interrelationships of tea microorganisms helps us to better understand the tea ecosystem, provide scientific basis for tea cultivation and processing, and further improve the quality and taste of tea. 2.2 Role of microorganisms in tea fermentation and catechin modification The fermentation process of tea leaves is a crucial stage that determines their quality and flavor, with microorganisms playing a key role in this process. Tea fermentation refers to the microbial fermentation of processed fresh tea leaves under specific environmental conditions. During this process, changes in the microbial community and their metabolic activities result in alterations in the chemical composition of tea leaves, giving rise to unique aromas and flavors. The main microorganisms involved in the tea fermentation process are Aspergillus spp and Penicilliumspp, which belong to the fungal kingdom. These fungi are natural microorganisms in tea, often found on tea trees, in soil, and in tea processing environments. They produce a variety of compounds through metabolic activity during tea fermentation, including the oxidase and enzymolysis enzymes of tea polyphenols (Huang et al., 2022). The metabolites of Aspergillus and Penicillium have have important influence on the fermentation process and quality of tea leaves. Aspergillus is mainly involved in the primary fermentation of tea, which decomposes the tea polyphenols in tea, produces pigments such as theophylavin and thein, and makes the color of tea turn from green to red. Penicillium, on the other hand, participates in the secondary fermentation of tea, which further decomposes theaflavins and teophyins, produce compounds with special aroma and taste, such as teasins and tefuscin. The microbial role in tea fermentation process is very complex and is influenced by many factors, including tea varieties, fermentation conditions and processing techniques (Tan et al., 2009). Therefore, controlling the community structure and metabolic activities of microorganisms during fermentation is one of the important links in tea processing. Through scientific fermentation control and microbial regulation, the flavor characteristics and quality of tea can be adjusted to make it more in line with the taste of consumers' preferences. 2.3 Impact of microbial communities on catechin composition Microbial communities play a significant role in tea leaves, participating not only in the fermentation process but also influencing the composition and content of catechins in tea leaves. Catechins are one of the main active constituents in tea leaves and hold great significance for the quality and nutritional value of tea. During the growth of tea leaves, a symbiotic relationship is established between the tea plant roots and soil microorganisms. Certain soil microorganisms, such as rhizobacteria and fungi, interact with tea plant roots, promoting nutrient uptake by decomposing organic matter and providing nutrients. This symbiotic relationship has a crucial impact on the synthesis and accumulation of catechins.
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