# Effect of Blue Light Intensity During Spreading on the Aroma of Green Tea
## 4 Discussion
The qualitative and quantitative analysis showed notable variations in the aroma components of the four green tea samples when exposed to different light conditions during spreading. In this study, MBL treatment increased both the total content and the variety of aroma compounds, suggesting that it enhanced the aroma intensity of green tea. This could primarily be due to variations in the quantity of aroma precursors and enzyme activity influenced by light conditions during spreading [9]. In addition, light treatment also impacted the volatile compounds' composition and content during spreading. MBL treatment led to a significant rise in alcohols and aldehydes, while HBL treatment caused a significant increase in ketones. In a similar manner, earlier studies indicated that blue light treatment, as opposed to DARK treatment, notably raised the levels of aldehydes, ketones and alcohols in black tea [33]. In plants, typical aromatic precursors are lipids, amino acids, geranyl/farnesyl pyrophosphate, and carotenoids, which can be converted into volatile compounds via the metabolic processes of lipid oxidation, amino acid breakdown, terpenoid synthesis, and carotenoid breakdown, respectively [34]. Therefore, the volatile compounds in tea can be categorized as FADVs, AADVs, VTs, and CDVs [35]. During withering, fresh leaves in vitro continue to exhibit strong synthesis, transformation, and metabolism of FADVs, AADVs, VTs, and CDVs [8; 36]. In this study, 16 important differential compounds were identified, including 6 FADVs, 6 VTs, 2 AADVs, 1 CDV, and 1 other. This indicated that FADVs and VTs had major contribution to the formation of green tea aroma under different blue light intensity treatments. Hexanoic acid ethyl ester, 5-ethyldihydro-2(3H)-furanone, hotrienol, delta-decalactone, coumarin, and (\(Z\))-2-octen-1-ol were recognized as primary FADV aroma compounds due to its high rOAVs. Hotrienol, (\(Z\))-2-octen-1-ol, delta-decalactone, and hexanoic acid ethyl ester were volatile fatty acid derivatives with green or grass odor. Under LBL and DARK treatment, the above three compounds accumulated in green tea, which might lead to the green and grass-like odor in green tea. Coumarin is a natural substance with a sweet, herb-like, and cherry blossom scent. It has been identified as a key compound contributing to the sweet aroma of Japanese and Chinese green tea [37]. Green tea treated with MBL had a notably higher coumarin content compared to other treatment groups, enhancing its sweet aroma of green tea. Furaneol, which imparts'sweet, fruity, and caramel' notes, is extensively found in berry fruits, like strawberry [6]. In Laoshan green tea, furaneol was identified as a key aroma compound [9]. 5-Ethyldihydro-2(3H)-furanone was only accumulated under LBL treatment, which may be the source of the sweet aroma of green tea under LBL treatment. Geraniol, _cis_-linal oxide (_furanoid_), _trans_-linal oxide (_furanoid_), nerol, linalool, and _E_-citral (geranial) were identified as the key VTs of aroma. The \"fruit sweet fragrance\" of green tea was mainly composed of linalool, linalool oxide, geraniol, and nerol [31]. Linalool has been extensively researched and found to be the compound that imparts a chestnut-like aroma [19]. Geraniol is a colorless oily liquid with a rose-like scent, and it is often detected in green tea. Geraniol has been reported to exhibit positive correlations with the Huangshan Maofeng grade [38]. Linalool, linalool oxide, and geraniol were found to accumulate under MBL treatment, possibly leading to the fruity and sweet aroma in green tea. In sunlight withering, the increased activity of geranyl pyrophosphate synthase and alcohol dehydrogenase was associated with an enhanced floral aroma due to the enrichment of terpene-catalyzed products and benzeneacetaldehyde concentration [39]. MBL treatment with green tea may reduce isopentenyl pyrophosphate and dimethylallyl pyrophosphate concentrations, resulting in elevated levels of linalool and geraniol.