Journal of Tea Science Research, 2024, Vol.14, No.5, 249-261 http://hortherbpublisher.com/index.php/jtsr 252 visualization of key components in black tea fermentation revealed that different fermentation times significantly influence the levels of theafuscin, thearubigin, catechin, caffeine, and soluble sugars (Yang et al., 2021). These findings highlight the importance of optimizing fermentation time to enhance the quality and flavor of tea. 4 Impact on Tea Flavor 4.1 Development of aroma compounds The development of aroma compounds during tea fermentation is influenced by various factors, including fermentation temperature, oxygen levels, and specific fermentation methods. For instance, the study by Qu et al. (2020) demonstrated that black tea fermented at 28 °C exhibited the highest sensory quality, with significant increases in VOCs contributing to its aroma. Similarly, the re-rolling treatment in the fermentation process was found to enhance the floral and fruity scents of Congou black tea by altering the levels of various VOCs, such as hexanoic acid and β-ionone (Chen et al., 2023). Additionally, the application of methyl jasmonate (MeJA) during tea processing significantly improved the aroma quality of green, oolong, and black teas by modulating the levels of key aroma compounds like benzyl alcohol and linalool (Shi et al., 2019). 4.2 Influence on taste profiles Fermentation conditions also play a crucial role in shaping the taste profiles of tea. Oxygen-enriched fermentation, for example, was shown to reduce the levels of bitter and astringent metabolites, such as catechins and phenolic acids, while increasing the concentration of theaflavins and amino acids, thereby enhancing the umami intensity of black tea (Chen et al., 2021). The study on autumn green tea revealed that fermentation with Eurotium cristatumsignificantly reduced astringency and improved the umami taste by oxidizing catechins and increasing theabrownins content (Xiao et al., 2021). Furthermore, a novel dynamic fermentation method (DFM) was found to enhance the sensory quality of Congou black tea by increasing the formation rate of theaflavins and thearubigins, which are crucial for the taste profile (Hua et al., 2021). 4.3 Sensory evaluation of fermented teas Sensory evaluation is a critical aspect of assessing the quality of fermented teas. The study by Qu et al. (2020) highlighted that black tea fermented at 28 °C received the highest scores for aroma and taste during sensory evaluation. Similarly, the sensory quality of fermented autumn green tea was significantly improved, with a notable increase in aroma quality and a reduction in astringency. The re-rolling treatment in the fermentation process also resulted in higher sensory scores for aroma quality in Congou black tea (Chen et al., 2023). Additionally, the application of MeJA during tea processing was confirmed by sensory evaluation to enhance the aroma quality of various tea types, including green, oolong, and black teas (Shi et al., 2019). In summary, optimizing fermentation conditions, such as temperature, oxygen levels, and specific fermentation methods, can significantly impact the development of aroma compounds, taste profiles, and overall sensory quality of tea. These findings provide valuable insights for improving tea flavor and quality through controlled fermentation processes. 5 Impact on Tea Quality 5.1 Physical attributes (color, texture) Fermentation conditions significantly influence the physical attributes of tea, including color and texture. For instance, the brightness of tea liquor is a critical quality attribute affected by fermentation parameters such as temperature and humidity. Studies have shown that maintaining optimal fermentation conditions can enhance the brightness and overall appearance of tea liquor. Specifically, a low fermentation temperature helps maintain a bright orange-red liquor color and promotes the accumulation of theaflavins and thearubigins, which are essential for the desirable color of black tea (Zhu et al., 2022; Saikia et al., 2023). Additionally, the texture of tea leaves can be altered through fermentation, with changes in the structure and color of tea dregs observed when fermented with specific fungi (Cui et al., 2021).
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