## 3 Results and Discussion
### OAV Analysis of the Differential Aroma Substances
There was no significant difference in linalool between spring tea (SH-S, FD-S) and autumn tea (SH-A, FD-A). It is worth noting that (\(E\))-linalool oxide was the only compound that showed significant differences in a two-by-two comparison of the four samples. (\(E\))-linalool oxide was identified as a key aroma compound in teas, which mainly exhibited floral, sweet, and fruity aromas. In this study, FD-A had the highest content of (\(E\))-linalool oxide, followed by SH-A, FD-S, and SH-S. This phenomenon showed that harvest season and tea cultivar may affect the formation path of (\(E\))-linalool oxide. Teas harvested in autumn contained more (\(E\))-linalool oxide than teas harvested in spring in both 'Sanhua1951' and 'Fudingdabai'. For black tea, a study shows that the sharp increase in the content of linalool in autumn tea is related to the increase in glycosidic aroma precursors with the growth of tea leaves [53]. This may be related to differences in tea cultivars, processing techniques, and detection methods. In addition to linalool and (\(E\))-linalool oxide, colimene is also derived from geranylpyrophosphate, liberated by ocimene synthase [54]. Ocimene was deemed the key differential odorant affecting the aroma quality of the black teas produced on different dates in the spring season [36]. In this study, the fourth OAV was colimene, possessing a herbal aroma, with a numerical range of 108.301-152.647 (Table 3), and there were no significant differences in a two-by-two comparison of the four groups. Moreover, the volatile compounds with OAV > 10 were (_E_, _E_)-2,4-nonadienal, undecylic aldehyde, decanal, methyl salicylate, and 3,5-Octadien-2-one, which contributed significantly to the aroma profile and dominated the flavor of white teas. Notably, undecylic aldehyde and 3,5-octadien-2-one were identified in spring teas (SH-S, FD-S), which were not identified in autumn teas (SH-A, FD-A). Inversely, (_E_, _E_)-2,4-nonadienal was identified in autumn teas (SH-A, FD-A), which were not identified in spring teas (SH-S, FD-S) (Table 3). As a lipid degradation product, (E, E)-2,4-Heptadien has contributed to the flowery attribute most and can be the key volatiles of Chinese green teas in different grades [55; 56] and Pu-erh tea at different storage times [57]. In this study, there was a significant difference in the OAV of (E, E)-2,4-heptadienal between SH-S and SH-A, while no significant differences were in other samples. According to the literature reports, (_E_, _E_)-2,4-heptadienal was the key aroma-active compound in food samples, such as red mullet, milk, and African _Oryza glaberrima_ rice [58; 59; 60], which the changes of content were caused by the living environment of animals and plants and processing methods. The changes in light and temperature in harvest seasons may also be the reason for the decrease in the content of (_E_, _E_)-2,4-heptadienal between SH-S and SH-A. Among 30 volatile compounds, based on the principles of OAV > 1, VIP > 1, and \(p\) < 0.05, for 'Sanhua1951', 18 volatile compounds were selected as the key differential volatile compounds in white teas between spring and autumn, including (_E_, _E_)-2,4-nonadienal, (_E_, _E_)-2,4-heptadienal, (_E_)-2-decenal, 2-undecen-1-al, (_E_)-Linalool oxide, geraniol, (_Z_)-jasmone, \(\alpha\)-ionone, \(\beta\)-ionone, \(\delta\)-cadinene, naphthalene, 2-pentylfuran, undecylic aldehyde, \(\alpha\)-cedrol, 3,5-octadien-2-one, 3-tridecanone, 5,6-epoxy-\(\beta\)-ionone, and 4-nonanolide. For 'Fudingdabai', 19 volatile components were selected as the key differential volatile components of white teas between spring and autumn, including Dimethyl sulfide, (_E_, _E_)-2,4-nonadien, (_E_)-2-decenal,2-undecen-1-al, (_E_)-Linalool oxide, geraniol, (_Z_)-jasmone, \(\alpha\)-ionone, \(\beta\)-ionone, \(\beta\)-pinene, \(\delta\)-cadinene, naphthalene, undecylic aldehyde, \(\alpha\)-cedrol, 3,5-octadien-2-one, 3-tridecanone, 5,6-epoxy-\(\beta\)-ionone, 4-nonanolide, and \(\beta\)-cyclocitral.