Dual mode unity-SPME-GC-MS unlocks the low-volatile flavour profiles of oolong, black, and Pu-erh teas: Revealing aroma diversity shaped by processing techniques

• DMU-SPME/GC-MS effectively targets low-volatility compounds for tea flavor. • DMU-SPME excels in extracting specific tea aroma compounds compared to HS-SPME. • DMU-SPME is helpful for the identification of unique flavor characteristics of tea. The flavour diversity of three types of tea (oolong, black, and Pu-erh teas) processed by different methods was comprehensively analysed using dual mode unity solid-phase microextraction (DMU-SPME) technology combined with gas chromatography-mass spectrometry (GC-MS). The optimal DMU-SPME extraction conditions included an extraction temperature and time of 60°C and 40 min, respectively, and the addition of 20% NaCl. DMU-SPME is more efficient than traditional headspace solid-phase microextraction (HS-SPME) in the extraction of low-volatility flavour compounds such as nerolidol (floral aroma), 6-pentyltetrahydro-2H-pyran-2-one (creamy aroma), jasminlactone (floral aroma), and methyl jasmonate (floral aroma). A comparative analysis of the flavour characteristics of the nine tea samples revealed similar flavour compound profiles in tea samples of the same type; however, different types of tea samples exhibited significantly different flavour compound profiles. Additionally, the DMU-SPME extracts more differential aroma compounds than HS-SPME and therefore provides effective support for the identification of tea flavours, offering a new technique with strong prospects for tea quality evaluation and classification.