Exploring the Effects of Compressing and Aging on the Aroma of Camellia nanchuanica Crude Tea and Its Tuo Tea Based on HS-SPME-GC-MS

To investigate the changes in aroma components of Camellia nanchuanica crude tea before and after compression and the effects of aging on the aroma of Tuo tea, traditional sensory evaluation combined with headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed for aroma analysis of tea samples in this study. A discriminant model was established through orthogonal partial least squares discrimination analysis (OPLS-DA), and characteristic aromas in different tea samples were screened based on variable importance in projection (VIP values) and odor activity values (OAV). Results showed that there were obvious differences in the aroma score of Camellia nanchuanica tea before and after compressing and aging at room temperature (P<0.05). A total of 114 aroma components were identified by HS-SPME-GC-MS, and compared with crude tea, the aroma types and contents of Tuo tea were significantly reduced after the compressing process, the loss of low-boiling-point aroma compounds, such as 1-octen-3-one was significant while the aroma profile of Tuo tea exhibited increased diversity after undergoing the aging process, with the presence of 1,2-dimethoxybenzene being a distinct characteristic in the aged Tuo tea samples. OPLS-DA based on 107 common aroma components could effectively distinguish different tea samples, based on the double criteria of VIP>1 and OAV>1, a total of 23 characteristic aroma components were screened, seventeen aroma components, including phenethyl alcohol and (E)-2-heptenal were identified as important contributors to the aroma of Camellia nanchuanica crude tea samples, while six aroma components including (E)-2-nonenal and (E)-2-octenal were identified as significant contributors to the aroma of Camellia nanchuanica Tuo tea samples. This study would provide a reference for the processing and storage of Camellia nanchuanica Tuo tea.