## 3 Results and Discussion
g \({}^{-1}\)DW)**} \\ \hline
8.966 & 900 & minimum 1 & _nf_ & of & 2.6 \(\pm\) 1.19 & \multicolumn{4}{c}{**Gree Tas to = 3**} & **Oulong Tota to = 0**} & **Hack Tota to = 3**} \\
3.346 & 903 & minimum 2 & _nf_ & of & 6.2 \(\pm\) 1.26 & \multicolumn{4}{c}{**nf**} \\
10.31 & 1022 & minimum 3 & _nf_ & of & 1.20 \(\pm\) 0.27 & \multicolumn{4}{c}{**nf**} \\
10.631 & 1028.9 & 1031 & _p_-to-coherence & 175.2 & Family, floral & 4.7 \(\pm\) 1.48 & \multicolumn{4}{c}{**nf**} \\
11.388 & 1075.1 & 1094.4 & _c_-finalized oxide & 188 & Fresh, floral & 3.55 \(\pm\) 0.53 & \multicolumn{4}{c}{**nf**} \\
11.876 & 1088.3 & 1000.1 & _n_-tom/loaded oxide & 227.6 & \multicolumn{4}{c}{**nf**} \\
12.772 & 1009 & 1006.7 & _n_-tom/loaded oxide & 199 & floscosc, locomotor & 2134.2 \(\pm\) 2.09 & \multicolumn{4}{c}{**nf**} \\
12.876 & 1018.5 & 1104 & _n_-tom/loaded oxide & 10-94 & Family & \multicolumn{4}{c}{**nf**} \\
12.691 & 1113 & 1109 & _n_-tom/loaded-13.7 & \multicolumn{4}{c}{**nf**} \\  & & & & & & & & \\  & & & & &  
A major difference between green tea and oolong tea making technology was the \"turning over\" step of oolong tea (Supplementary Figure S1). Some volatile contents from oolong tea, including hotrienol, dodecane, 2,6-dimethyl-3,7-octadecine-2,6-diol, hexyl butanoate, 1,3-bis(1,1-dimethylethyl) benzene, 2,5-dihydro-2,5-dimethoxyfuran, hexyl hexanoate, (_E_)-\(\beta\)-farnesene, \(\delta\)-cadinence, (3E,7E)-4,8,12-trimethylrideca-1,3,7,11-tetraene, and _cis_-3-hexaryl n-octanoate, were significantly higher than that of green tea (Table 1). This suggested that the \"turning over\" treatments could activate these volatile syntheses. Meanwhile, other volatile contents from oolong tea, including (_E_)-4,8-dimethylnona-1,3,7-triene, (_Z_)-3-hexenyl butanoate, methyl salicate, (_E_)-geraniol, _cis_-3-hexenyl hexanoate, \(\beta\)-caryophyll, trans-\(\beta\)-ionone, _cis_-jasmin lactone, naphthalene, (_E_)-\(\gamma\)-bisabolene, \(\alpha\)-cadinene, germacrene B, _E_-2-hexenyl benzoate, methyl jasmonate, and _cis_-3-hexenyl salicate, were lower than that of green tea, suggesting that the \"turning over\" step could also facilitate these volatile's evaporation. There were 13, 12, and 17 volatiles detected from green tea, oolong tea, and black tea respectively, but below the detection limit from fresh tea leaves (Table 1, Supplementary Figure S2). These data demonstrated that postharvest tea processing facilitate NEVs formation and accumulation. Interestingly, oolong tea was generally regarded to be more aromatic than green tea or black tea [22]. However, its total aroma contents were significantly lower than that of green tea or black tea (Figure 1). Thus, the total volatile contents did not positively correlate with their aroma quality. Other factors, such as the volatile compositions, could play a larger role to influence tea's aroma characteristics. To identify which volatiles could confer an aroma note in a standard sensory evaluation, the odor-activity value (OAV) was calculated. The odor activity values (OAVs) are the ratios of concentration found in the food matrix to its odor detection threshold [23]. The odor detection threshold is the lowest concentration of a certain odor compound that is perceivable by the human sense of smell. The OAV is commonly used to estimate odor potency, their values from fresh tea leaves and made teas are listed in the order of retention time from low to high in Table 2. The volatiles with OAV \(>\) 1 were generally regarded as contributors to the aroma characteristics. Thus, linalool, (_E_)-geraniol, indole, _cis_-jasmone, _trans_-\(\beta\)-Ionone, and \(\alpha\)-farnesene could be the potential contributors to the aroma quality of _Tieguanvin_ green tea; linalool, _cis_-jasmone, and \(\alpha\)-farnesene could be the potential contributors to the aroma quality of _Tieguanvin_ oolong tea; linalool, _trans_-linalool oxide  
Figure 1: Total volatile contents from fresh leaves, green tea, oolong tea, and black tea. Data are expressed as average \(\pm\) standard deviation.