Abstract:

A method to analyze the volatile components in Minnan oolong tea was developed based on headspace solid phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOF MS). Volatile compounds of 48 oolong tea samples with different qualities and production seasons from five varieties (Tieguanyin, Huangjingui, Benshan, Maoxie and Meizhan) were extracted by HS-SPME and analyzed by GC×GC-TOF MS. More than 2000 peaks were obtained from each sample, and 51 common compounds were tentatively identified by comparison with the standard mass spectrum databases, retention indices and structure spectra. The projection score of the common compounds obtained from principal component analysis (PCA) had presented a straightforward classification trend for different oolong tea varieties. In addition, 9 compounds which had significant impact on the classification were selected by stepwise discriminate analysis, and used as variables to establish four discriminated functions by Fisher's discriminate analysis (FDA). The accuracy for the recognition of 48 samples was 97.9%. The results had demonstrated the feasibility of the method to be used to discriminate the oolong tea varieties.

Key words: comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOF MS), Fisher's discriminate analysis, headspace solid phase microextraction (HS-SPME), Minnan oolong tea, principal component analysis (PCA), volatile components