Aroma-Driven Differentiation of Wuyi Shuixian Tea Grades: The Pivotal Role of Linalool Revealed by OAV and Multivariate Analysis

Abstract

Wuyi Shuixian tea, a premium oolong tea known for its complex floral-fruity aroma, exhibits significant quality variations across different grades. This study systematically analyzed the aroma characteristics and key fragrant compounds of four grades (Grand Prize SA, First Prize SB, Outstanding Award SC, and Non-award SD) using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), odor activity value (OAV) analysis, and multivariate statistical methods. A total of 159 volatile compounds were identified, with similar compound categories but distinct concentration gradients between grades. OAV-splitting analysis (based on OAV ≥ 1 as the threshold for aroma activity) identified β-ionone (fruity), octanal (fatty), and linalool (floral) as core aroma-active contributors, as their OAV values significantly exceeded 10 in awarded grades (SA, SB, SC), indicating dominant roles in sensory perception. Notably, linalool, a floral marker, showed a concentration gradient (SA > SB > SC) and was absent in SD, serving as a critical determinant of grade differentiation. Orthogonal partial least squares-discriminant analysis (OPLS-DA) further distinguished awarded grades (SA, SB, SC) by balanced fruity, floral, and woody notes, while SD lacked floral traits and exhibited burnt aromas. This classification was supported by hierarchical clustering analysis (HCA) of volatile profiles and principal component analysis (PCA). Electronic nose data validated these findings, showing strong correlations between sensor responses (W5S/W2W) and key compounds like hexanal and β-ionone. This study elucidates the molecular basis of aroma-driven quality grading in Wuyi Shuixian tea, providing a scientific framework for optimizing processing techniques and enhancing quality evaluation standards. The integration of chemical profiling with sensory attributes advances precision in tea industry practices, bridging traditional grading with objective analytical metrics.

Keywords: Wuyi Shuixian tea; aroma profiling; flavor-active compounds; odor activity value (OAV); quality grading.

Figure 1

Electronic nose analysis of three grades of Wuyi Shuixian tea. (A) Principal Coordinates Analysis (PCoA) illustrating the differentiation between grades; (B) Radar chart depicting sensor responses (Normalize the data). SA: Grand Prize, SB: First Prize, SC: Outstanding Award, and SD: Non-award. W1C: Sensitive to aromatic compounds (benzenes), W5S: Sensitive to nitrogen oxides, W3C: Sensitive to ammonia water and aromatic components (amines), W6S: Selective for hydrogen (hydride), W5C: Sensitive to alkanes and aromatic components (short-chain alkanes), W1S: Sensitive to methane (methyl group), W1W: Sensitive to sulfides (inorganic sulfides), W2S: Sensitive to ethanol, W2W: Sensitive to organic sulfides, W3S: Sensitive to alkanes (long-chain alkanes).

Figure 2

Analysis of total volatile compounds in different grades of Wuyi Shuixian tea (n = 3 per grade). (A) The total ions chromatogram, (B) Heat map of the volatile compounds, (C) VOCs Venn diagram; (D) Score scatter plot for PCA model (total); (E) PCA analysis of different grades of samples; (F) VOCs concentration line chart; (G) Content analysis of the ten types of volatile compounds. SA: Special prize; SB: first prize, SC: Excellent prize; SD: unnominated.

Figure 3

OPLS-DA analysis illustrating the differences in grades of Wuyi Shuixian tea (n = 3 per grade). (A) Test plot of OPLS-DA model for volatile components at different grades of Wuyi Shuixian tea; (B) The OPLS-DA model cross-validation results; (C) Scores OPLS-DA plot for analysis of within- and between-group differences in the different grades of Wuyi Shuixian tea; (D) OPLS-DA S-Plot screening of key volatile components differentiating various grades of Wuyi Shuixian tea.

Figure 4

Volatile components with OAV > 1 and their contents in different grades of Wuyi Shuixian tea (ug/kg).

Figure 5

Analysis of the aromatic components and electronic nose correlation of different grades of Wuyi Shuixian tea. *: p < 0.05, **: p < 0.01, ***: p < 0.001.

Figure 6

Radar chart of index of odor I(o) in different grades of Wuyi Shuixian tea. (A) Radar map of odor contribution of key compounds; (B) Radar map of odor contribution of SA; (C) Radar map of odor contribution of SB; (D) Radar map of odor contribution of SC; (E) Radar map of odor contribution of SD.