Comparative Analysis of Volatile Compounds in Tieguanyin with Different Types Based on HS-SPME-GC-MS

Area of Science:

• Food Chemistry
• Analytical Chemistry
• Agricultural Science

Background:

• Tieguanyin (TGY) oolong tea is prized for its distinct aroma and flavor.
• Understanding the volatile compound profiles is crucial for differentiating TGY varieties and assessing quality.
• Previous research has explored oolong tea volatiles, but specific markers for TGY quality and fermentation require further elucidation.

Purpose of the Study:

• To analyze and compare volatile compounds in different types of Tieguanyin (TGY) oolong tea and other oolong teas.
• To identify key volatile compounds that differentiate TGY from other oolong varieties.
• To investigate the relationship between volatile profiles, fermentation degree, and tea grade in TGY.

Main Methods:

• Solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS) was employed for volatile compound extraction and analysis.
• Chemometrics, including variable importance in projection (VIP) and aroma character impact (ACI), was used for data analysis.
• Volatile compound concentrations were quantified and correlated with tea type, fermentation level, and grade.

Main Results:

• Tieguanyin (TGY) exhibited higher levels of heptanal, (E,E)-2,4-heptadienal, (E)-2-octenal, indole, and (E)-nerolidol compared to other oolong teas.
• Increasing fermentation led to a slight decrease in total volatile compounds, particularly floral compounds, with higher monoterpenoids in heavily fermented tea and higher sesquiterpenes and indole in lightly fermented tea.
• Special-grade TGY contained more aroma compounds, primarily alcohols (28%), and key volatiles like (E,E)-2,4-heptadienal, (E)-2-octenal, benzeneacetaldehyde, and (E)-nerolidol distinguished different grades.

Conclusions:

• Specific volatile compounds, including aldehydes, indole, and nerolidol, serve as important markers for identifying Tieguanyin (TGY) oolong tea.
• The volatile profile, particularly the ratio of monoterpenoids, sesquiterpenes, and indole, effectively distinguishes the fermentation degree of TGY.
• (E,E)-2,4-Heptadienal, (E)-2-octenal, benzeneacetaldehyde, and (E)-nerolidol are critical for differentiating TGY grades, contributing to a better understanding of TGY aroma profiles.