# Analysis of the Changes in Volatile Components During the Processing of Enshi Yulu Tea
## 3 Results and Discussion  
### Profile Analysis of Volatile Components  
After peak matching and pollutant removal, 242 reliable volatile components were identified (Table S1). Based on chemical structure, these components were categorized into 11 classes (Figure 1A, Table S1), among which the largest was esters (45 counts, 18.60%), followed by alcohols (43, 17.77%), ketones (41, 16.94%), alkenes (32, 13.22%), and aldehydes (20, 8.26%), which collectively accounted for >8%. There were over 10 alkanes (18, 7.44%), aromatic (15, 6.20%), and oxygen heterocycles (10, 4.13%); quantities of lactones (7, 2.89%), nitrogen heterocycles (6, 2.48%), and acids (5, 2.07%) were relatively low (Figure 1B). Consistent with these findings, further validating test-result reliability, is that higher proportions of esters, alcohols, and ketones have been reported as aroma components in steamed green tea [3; 17]. Levels of various volatile compounds, including alcohols, aldehydes, ketones, esters, lactones, aromatic hydrocarbons, alkanes, olefins, and acids, significantly decreased from FTL to RTL stages, particularly during the steaming process (Figure 2). During the shaping process, these compounds declined further while volatiles of oxyheterocycles and nitrogen heterocycles increased (Figure 2). During drying, there was a significant increase in alcohol, ketone, alkane, acid, oxyheterocycle, and nitrogen heterocycle contents and a notable decrease in aromatic hydrocarbon contents; other compounds remained relatively unchanged (Figure 2). These findings align with research on changes in aroma components during the drying process of roasted green tea [14]. Overall, the total aroma gradually decreased from FTL to shaping but increased after drying. The aroma of tea is related to the relative proportions of different volatiles. Whether fresh leaves or finished tea, alcohol volatiles have the highest relative content (approximately 40%), followed by aldehydes, esters, ketones, and others (Table 1). [PERSON] et al. found that the steamed green tea has the highest proportion of alcohols (50.02%), followed by esters (14.32%) [3], possibly because there are high concentrations of alcohols, aldehydes, ketones, and other aromatic components in fresh tea leaves [18]. During processing from FTL to the DTL, the proportional contributions of aromatic hydrocarbons, alkanes, aldehydes, ketones, and nitrogen heterocycles trend upwards, and olefins, alcohols, acids, esters, and lactones trend downwards. After completion of the drying process, levels of aromatic hydrocarbons, aldehydes, and lactones decreased significantly while those of alkane compounds, acids, and oxygen heterocycles increased; levels of remaining compounds changed little. A substantial increase in oxygen and nitrogen acyclic groups during  
Figure 1: Numbers (**A**) and percentage (**B**) of different aroma classification in Enshi Yulu tea. shaping and drying processes can be attributed to an enhanced Maillard reaction during these steps [19; 20]. The influence of volatile components on aroma quality is often closely related to their contents. Of individual aroma components in the DTL stage, the proportional contributions of the top 40 components (with proportion \(\geq\) 0.44%) are presented in Table 2. Of these aroma components, linalool, geraniol, phenylmethanol, oct-1-en-3-ol, benzaldehyde, 2-phenylacetaldehyde, \(\beta\)-ionone, (\(2E\))-non-2-enal, _trans_-linalool oxide (furanoid), _cis_-3-hexenyl hexanoate, hexanal, (\(Z\))-3-hexen-1-ol, naphthalene, _trans_-linalool oxide (pyra-noid), and hexan-1-ol are compounds with higher relative contents in green tea [3; 21; 22; 23; 24; 25; 26; 27], and _cis_-3-hexenyl valerate is a compound with higher relative content in Yunnan black tea [28]. Most of these components present pleasant aromas. For example, linalool, ger  
iol, phenylmethanol, benzaldehyde, 2-phenylacetaldehyde, \(\beta\)-ionone, and _cis_-3-hexenyl valerate have pleasant fragrances of flowers, fruits, and sweetness (Table 2).