# Effect of Blue Light Intensity During Spreading on the Aroma of Green Tea
## 4 Discussion  
Tea is the second most widely consumed drink, surpassed only by water, in many societies [23]. Around the globe, its special flavor, fragrance, and health advantages are highly prized [24]. Typically, green tea quality is assessed by examining its color, aroma, taste, shape, and the appearance of its steeped leaves. The type of aroma is a crucial aspect of green tea quality, significantly influencing its market price and consumer preference [25]. Green tea's scent [19] can be categorized into different types, such as floral, sweet, chestnut-like, and fresh aromas. Spreading, fixation, rolling, and drying all impact flavor; spreading receives more focus. As spreading occurs, volatile compounds, amino acids, and glycosides experience notable changes, which may lead to an increase in amino acids, suppression of catechin and flavonoid production, and a decrease in the phenol-to-amine ratio [26]. Figure 8: Interaction analysis of key volatile compounds based on correlation coefficients. (**A**) Analysis of interactions between key volatile compounds under HBL treatment during spreading. (**B**) Analysis of interactions between key volatile compounds under MBL treatment during spreading. (**C**) Analysis of interactions between key volatile compounds under LBL treatment during spreading. The numbers in the figure correspond to the serial numbers of the substances in Table 2.  
Part of the aroma components of tea are inherent in fresh leaves, and the other part is mainly formed during processing [27]. The initial step in processing green tea, spreading, has a direct impact on the tea quality. After spreading, the leaves start to wilt, their texture shifts from firm to soft, their color transitions from bright green to dark green, and ultimately, the leaves lose their greenness entirely. The aroma is also released, and the moisture level of the spread leaves decreases to \(70\pm 2\%\), which is a moderate level, setting the stage for the next step in the fixation process [28]. In traditional processing, solar withering is widely used in the manufacturing process of tea to improve the overall quality. Indoor trough withering compensates for the environmental drawbacks in natural withering and enhances both efficiency and quality [5]. At present, the positive effects of different light conditions on tea quality have been confirmed, so the installation of LED lamps in traditional indoor withering chambers has been applied. The content and composition of volatile compounds are easily affected by the light conditions during different withering conditions. Red light and UV-B withering could enhance the activity and up-regulate the expression of \(\beta\)-primeverosidase and \(\beta\)-GLU during withering, leading to the release of free GBy(s)gycosides, such as linalool and its oxides [13; 29]. During the green tea spreading process, the red light was beneficial to accumulate components that produce a chestnut-like aroma [30]. Linalool synthase (_CsLIS2_, _CsLIS3_, _CsLIS4_) and farresene synthase (_CsFS5_, _CsFS10_) were significantly up-regulated in spreading leaves after LTY (low temperature + yellow light) treatment and significantly improved the aroma quality of green tea products [31]. The pleasant scents of green tea are frequently characterized as tender and fresh, with notes like chestnuts and orchids. The unpleasant scents of green tea are frequently characterized as grassy, dull, and over-fired. An experienced sensory panel can subjectively differentiate these various aroma types, or they can be objectively distinguished using analytical instruments and chemometric techniques [32]. In the MBL treatment, the floral aroma was significantly more intense than in the DARK treatment, which might be attributed to higher linalool concentrations. Furthermore, the greater amounts of rerol might contribute to the stronger fruity aroma in HBL treatment. This discovery aligned with related studies, indicating that blue light treatment was the most effective in enhancing the floral aroma [12].