## 4 Discussion
### The Selection of Volatile Compounds and Their Correlation Between Different TSH Grades  
Benefiting from full fermentation, black tea possesses the most diverse and complex aroma profile among the six major tea categories [44]. Unlike traditional black teas that pursue bright red liquor and evenly reddish infused leaves, innovative black teas (e.g., MKH, Golden Junmei) retain more floral aroma compounds through light fermentation [45]. In contrast, the comprehensive fermentation in traditional black tea results in more profound and holistic volatile accumulation and interactions. Our aroma profiling revealed that Methyl salicate, Geraniol, Linalool, and Phenylethyl alcohol exhibited notably high concentrations.  
Methyl salicate, which contributes a fresh, minty, and slightly floral scent with wintergreen notes (reminiscent of peppermit or eucalyptus), may be associated with the heavier withering degree during TSH processing--[PERSON] et al. [46] showed that moderate withering intensity facilitates the accumulation of such key aroma components. Geraniol, a key component of rose oil that imparts \"rich,\" \"romantic,\" and \"elegant\" aromatic traits, is positively correlated with raw material tenderness: [PERSON] et al. [47] confirmed that younger plucking standards in black tea (indicating more tender leaves) are directly associated with higher geraniol content.  
Our previous research identified Methyl salicate as a key volatile marker distinguishing traditional black tea (Fuyun No. 6 cultivar) from innovative varieties [48]. The relative abundance of Geraniol and Linalool reflects varietal characteristics (large- vs. small-leaf), seasonal variations, and plucking standards [49; 50]. Their consistently high levels across TSH grades suggest the use of premium spring shoots and potential involvement of Fuyun No. 6 cultivar--a variety genetically related to _Camellia sinensis_ var. assamica--evidenced by linalool's marked predominance over geraniol. Phenylethyl alcohol contributes a characteristic rose-like note to premium TSH's refined aroma profile. As demonstrated by [PERSON] et al. [51], this compound plays a crucial role in sun-withered black teas. These findings collectively highlight how cultivar selection and precise processing techniques fundamentally shape TSH's distinctive aromatic qualities.  
Furthermore, we identified volatile compounds exhibiting strong correlations with specific sensory aroma attributes. Notably, V112 [(_E_)-geranic acid methyl ester (floral)] and V108 [1,6-dimethyl-4-(1-methylethyl)-naphthalene (aromatic)] both demonstrate characteristic floral or aromatic profiles. [PERSON]'s study [52] confirmed (_E_)-geranic acid methyl ester as a signature aroma compound in Jiangxi's traditional Ninghong Golden Hao tea. This compound has also been detected in traditional Hunan Caicha black tea and Anji black tea products. We therefore propose that V112 represents a characteristic volatile in traditional black teas, making significant contributions to TSH's tender sweet and floral notes. Although V137 shows correlations with multiple aroma attributes, this compound remains unreported in existing literature.  
Additionally, among the 29 volatile compounds strongly correlated with tea grades, 19 volatile compounds exhibited characteristic odor profiles. Notably, compound V101 (hexanoic acid, methyl ester) represents a typical aliphatic volatile with a relatively high odor threshold. With future technological advancements, these distinctive and readily detectable volatiles could serve as reliable markers for evaluating tea grade quality.