## 3 Results and Discussion  
### Sensory Evaluation and Electronic Nose Analysis of Lapsang Souchong Black Tea of Different Grades  
The sensory evaluation results (Figure 1a) demonstrate a distinct quality ranking among the Lapsang Souchong black tea samples, with super-grade (A) tea receiving the highest ratings across all evaluated sensory characteristics, followed by first-grade (B) and second-grade (C). The assessed attributes--shape, soup color, aroma, taste, and leaf base--show a consistent ranking of A > B > C. The overall sensory scores corroborate this pattern: super-grade scored 94.30, first-grade 85.05, and second-grade 76.26. These findings indicate that higher-grade Lapsang Souchong black teas possess superior sensory qualities, including a more intense aroma, a well-balanced taste, and enhanced visual appeal in soup color and leaf integrity. The pronounced differences in sensory attributes underscore the critical role of quality control and grading in promoting consumer satisfaction with higher-grade teas. Utilizing electronic nose technology to assess the volatile compounds present in the tea samples provided quantitative support for the sensory evaluation results. Electronic noses are commonly employed in food quality assessments and have shown efficacy in differentiating volatile profiles across various food products, including tea, wine, and coffee [3; 13; 14; 15]. In this study, electronic nose analysis (Figure 1b,c) was utilized to compare the aroma profiles of the three grades of tea. Principal component analysis (PCA) revealed that the first principal component (PC1) accounted for 66.3% of the total variance, while the second principal component (PC2) explained an additional 21.5%. This analysis confirmed that volatile compounds, especially those related to aroma, play a pivotal role in distinguishing between tea grades. The clustering of data points along the first two principal components illustrates the strong relationship between aroma profiles and tea grades, reinforcing the idea that aroma significantly influences grade classification. The radar chart (Figure 1c) further depicts the differences in sensor response values, which correlate with the concentrations of specific volatile compounds identified in the tea samples. Super-grade tea (A) displayed the highest sensor response values for components related to nitrogen oxides and terpenoids, followed by first-grade (B) and second-grade (C). This suggests that the higher levels of terpenoids and nitrogen-containing compounds in the super-grade tea contribute to its superior aroma profile, aligning with previous research identifying terpenoid content as a key factor in determining the quality of black tea [16; 17]. Terpenoids, recognized for their floral, fruity, and herbal notes, significantly enhance the aromatic complexity of premium black teas. The diminished sensor responses  
Figure 1: Sensory evaluation and electronic nose analysis of three grades of Lapsang Souchong black tea. (**a**) Radar chart displaying sensory scores. (**b**,**c**) Electronic nose evaluation results: (**b**) principal component analysis (PCA) illustrating the differentiation among grades; (**c**) radar chart depicting sensor responses. Grades A, B, and C correspond to special grade, first grade, and second grade, respectively. in lower-grade teas imply that these important volatile compounds are present in lesser quantities, resulting in a less complex and less appealing aroma. In summary, the sensory evaluation combined with electronic nose analysis offers a comprehensive view of the quality distinctions among the different grades of Lapsang Souchong black tea. The observed correlation between sensory attributes and the concentrations of volatile compounds emphasizes the value of both subjective (sensory) and objective (electronic nose) assessments in tea quality grading. The electronic nose's ability to accurately identify key aroma compounds, such as terpenoids, establishes it as a valuable tool in the tea industry for quality control and grade differentiation.