# Effect of Mechanical Damage in Green-Making Process on Aroma of Rougui Tea
## 3 Results  
### Analysis of Content of Volatile Compounds in Tea Leaves  
In this study, the aroma compounds of SY, LY7, CK7 and the finished tea were as shown in Table S3, including 15 esters, 12 alcohols, 5 aldehydes, 3 ketones, 4 olefins and 3 heterocycles. Compared with SY, esters, alcohols, aldehydes and ketones with pleasant flowery and fruity aroma compounds in LY7 and CK7 were significantly increased, and the content of aroma compounds in LY7 was significantly higher than that in CK7. Nerolido, jasmine lactone, indole, 2-isopropenyl-5-methyl-4-hexenol, farresene, methyl salicate, jasmonone, acetic acid hexyl ester, (E)-3-hexenyl butyrate and hexanoic acid hexyl ester were the main aroma compounds that had accumulated at the end of green-making and spreading, all of which had a strong floral and fruity aroma. Terpene derivatives are an important component of the tea aroma and one of the main substances for the formation of RGT's fruity aroma characteristics. Volatile terpenoids were detected in the samples, including nerolido, farresene, linalool and oxidation products, \(\beta\)-ocimene and so on. The content of nerolido in LY7 and in CK7 showed a significant difference. Farresene is a common sesquiterpene aromatic substance in RGT [28]. The present study detected that \(\alpha\)-farresene and (E)-\(\beta\)-farresene were increased at the end of green-making and spreading. Linalool is an important monoter aroma substance in tea [29]. Two linalool oxides and dehydrogenated linalool were detected in this experiment, and, compared with SY, the content of these volatile substances in LY7 and CK7 was increased. The phenylalanine metabolic pathway is an important pathway for the synthesis of aroma compounds in plants, and the related aroma compounds are phenylethyl alcohol, benzyl alcohol, benzaldehyde, phenylacetaldehyde, methyl salicate and so on. After the RGT fresh leaves were withered, the aroma compounds were significantly increased during the green-making and spreading process, and their content in LY7 was significantly higher than that in CK7. Phenylalanine produces trans-cinnamaldehyde under the action of phenylalanine ammonia lyase, and methyl salicate is synthesized by a multi-step reaction [30]. Compared with SY, the methyl salicate content in LY7 and CK7 increased significantly, which indicated that mechanical injury and dehydration could promote the synthesis of related products in the phenylalanine metabolic pathway. Studies have shown that mechanical injury and low-temperature stress can promote the accumulation of indole, jasmine lactone, nerolido and volatile fatty acid derivatives during the RGT manufacturing process [31]. In this study, jasmine lactone, jasmone, aliphatic alcohols and esters, which were related to the oxidative degradation of fatty acids [32], showed an increasing trend throughout the manufacturing process, and this was most obvious during the green-making process. Continuous damage in the process of green-making induces the transcription of genes related to jasmonic acid biosynthesis, which can promote the formation of terpenoids [33]. In this study, the content of jasmonic acid derivatives and the main volatile terpenoids in the LY group increased, which was beneficial for the formation of the quality characteristics of the floral and fruity aroma. The results of GC-TOF-MS showed that long-term mechanical injury and dehydration could significantly increase the terpene terpenoids and ester compounds, which are the main aroma components of RGT [34], and this was more obvious during the green-making process. While the content of most aroma components decreased in DM and ZM, this may have led to the loss of the volatile compounds under the action of the subsequent high temperatures. In this study, the sensory evaluation of the finished tea revealed that ZM had a more fragrant and lasting aroma and an obvious flowery and fruity flavor, while DM showed a clean and refreshing aroma, which was directly related to the type and content of the aroma compounds.