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Food Chem. 2013 Dec 1;141(3):2060-5. doi: 10.1016/j.foodchem.2013.05.054. Epub 2013 May 24.
Factors such as fermentation methods, geographical origin and season can affect the biochemical composition of tea leaves (Camellia sinensis L.). In this study, the biochemical composition of oolong tea during the manufacturing and fermentation process was studied using a non-targeted method utilising ambient ionisation with a direct analysis in real time (DART) ion source and mass spectrometry (MS). Caffeine dominated the positive ionisation spectra throughout the manufacturing process, while the negative ion spectra collected during manufacturing were rich in ions likely to be surface lipids. Correlation analyses on the spectra revealed two volatile compounds tentatively identified as indole and geranic acid, along with ammonium and caffeine clusters/adducts with geranic acid that increased in concentration during the fermentation stages of the process. The tentative identifications were assigned using a combination of DART-ion-trap MS(n) and DART-accurate mass MS(1) and MS(2) on tea samples and standard compounds. This study highlights the potential of DART-MS to rapidly monitor the progress of complex manufacturing processes such as tea fermentation.
发酵方法、地理起源和季节等因素都会影响茶叶（Camellia sinensis L.）的生化成分。本研究采用非靶向方法，利用大气压离子化直接实时分析（DART）离子源和质谱（MS），研究了乌龙茶在制造和发酵过程中的生化成分。在整个制造过程中，咖啡因主导了正离子化谱，而在制造过程中收集的负离子谱富含可能是表面脂质的离子。对谱的相关分析揭示了两种挥发性化合物，它们可能是吲哚和香叶酸，以及在发酵过程中浓度增加的铵和香叶酸与咖啡因的簇/加合物。这些暂定的鉴定是通过对茶样和标准化合物进行 DART-离子阱 MS(n)和 DART-精确质量 MS(1)和 MS(2)的组合来完成的。本研究强调了 DART-MS 快速监测复杂制造过程（如茶叶发酵）进展的潜力。
