## 3 Results and Discussion
### Volatile Detection of Different Oolong Tea Samples
With regard to fatty acid derived volatiles (FADVs), the two groups exhibited extremely significant differences (\(p<0.01\)) in compounds such as Butanoic acid hexyl ester, (Z)-3-Hexenyl hexanoate, (Z)-3-Hexenyl (Z)-3-hexenoate, and (Z)-Jasmone, while showing no difference (\(p>0.05\)) in 1-Heptanol, 1-Octen-3-ol, trans,(E)-2,\(A\)-Heptdienal, (Z)-3-Hexenyl-\(\alpha\)-methylbutyrate, (Z)-3-Hexenyl isovalerate, Hexanoic acid hexyl ester, and (E)-2-Hexenyl. All the four significantly different metabolites have a fruity odor, with (Z)-3-Hexenyl hexanoate and (Z)-Jasmone as the main compounds in lipid metabolism due to their high content. Among the aroma compounds with no differences between the two groups, hexanoic acid hexyl ester, (E)-2-Hexenyl hexanoate and (Z)-3-Hexenyl-\(\alpha\)-methyl butyrate all have a green odor. These results indicate that these different aroma compounds in FADVs may be among the factors responsible for the fruity aroma differences involved in the suitability of oolong tea cultivars. Regarding carotenoid derived volatiles (CDVs), the two groups had extremely significant differences (\(p<0.01\)) in the compounds of \(\beta\)-Ionone (woody, violet), (Z)-Geranyl acetone (Floral, hay-like), 6-methyl-5-hepten-2-one, and (r,s)-5-ethyl- 6-methyl-3e-hepten2-one, and a significant difference (\(p<0.05\)) in \(\alpha\)-ionone (woody, hay-like). Among these compounds, \(\beta\)-ionone and (z)-geranyl acetone had a higher content with a floral and woody aroma. \(\beta\)-ionone was considered to contribute significantly to the black tea aroma [21] as a carotenoid metabolite in black tea. These aroma compounds can be assumed to have greatly affected the differences between woody and floral odors in the samples. In this study, the two groups were also found to differ extremely significantly (\(p<0.01\)) in the aroma compounds of 2-pentylfuran, octanal, decanal, (e, e)-2,4-nonadienal, (z)-2-decenal, methyl inerate, e-2-undecenal, and (e)-2-dodecenal, but with no significant differences (\(p>0.05\)) in dodecane and isoeigenol. 2-pentylfuran has a bean-like, fruity, and green odor, which may be produced in the process of fixing or drying as a thermal reaction product [24]. Alkenal compounds mainly include decanal, (z)-2-decenal, (e)-2-undecenal, and octanal. Among them, decanal has a flowery and fruity odor, (z)-2-decenal has a fruity or fat odor, (e)-2-undecenal has a cabbage odor, and octanal has a citrus or green odor. These furans and alkenals may also have affected the aromas of tea samples of different suitability. In this study, it was shown that hs-spme-gc-ms could significantly distinguish the content differences of aroma compounds between the products of tea cultivars differing in suitability for making oolong tea, with 47 aroma compounds being significantly different between the two groups. If we adopt more advanced analytical means in future (eg gc-ims), more different substances may be obtained according to this work [25]. Some aroma compounds in oolong tea (such as indole, nerolidol, farnesene, etc.) are synthesized de novo in the withering process due to mechanical damage or low temperature environment [3; 23]; other compounds (such as furans, fatty aldehydes, etc.) belong to thermochemical reaction products, which are mainly synthesized during thermal processing, such as in fixing and drying after withering [26]. Therefore, the aroma difference in oolong tea cultivars of different suitability can be attributed to the differences in the synthesis of related substances in the two aforementioned processes.