多环芳烃在茶树鲜叶及绿茶加工过程中残留水平研究

利用气相色谱-串联质谱联用仪监测了茶树鲜叶及其绿茶加工中多环芳烃(PAHs)的残留水平。结果表明,不同地区茶树一芽二叶样品PAHs含量差异明显,产地环境PAHs污染程度对茶鲜叶PAHs含量影响较大。茶芽、嫩叶、老叶PAHs含量分别在40.5~52.8μg·kg~(-1)、50.0~67.4μg·kg~(-1)和91.5~97.6μg·kg~(-1)之间,PAHs含量大小顺序为老叶嫩叶芽。汽车尾气对交通公路旁茶树芽和嫩叶PAHs含量影响较大,且对50 m范围内茶树鲜叶影响更明显。电加热干燥模式下,水分散失和PAHs挥发是影响绿茶加工过程中PAHs含量的两个关键因子。加工环节过后,茶叶PAHs含量由61.0μg·kg~(-1)上升到166.1μg·kg~(-1)。摊放和干燥过程中PAHs大量挥发,造成茶叶干重中PAHs残留量由292.0μg·kg~(-1)降低到171.9μg·kg~(-1)。

Residue Pattern of Polycyclic Aromatic Hydrocarbons in Tea Leaves during Green Tea Manufacturing Process

Residues of polycyclic aromatic hydrocarbons (PAHs) in fresh tea leaves and green tea during manufacturing process were determined by gas chromatography–tandem mass spectrometry. Results showed that considerable variations of PAHs were identified in tea samples (a bud and two leaves) from different locations, indicating the contamination levels in the tea producing areas might significantly affect PAH residues in fresh tea leaves. The variations of PAHs contents in tea buds, tender leaves and mature leaves were 40.5-52.8 μg·kg-1, 50.0-67.4 μg·kg-1 and 91.5-97.6 μg·kg-1, respectively. The order of PAHs contents follows as mature leaves>tender leaves>tea buds. Vehicle exhaust was hypothesized to have a direct effect on PAH residues in tea buds and tender leaves, as their levels were extremely high within 50 m around the roads. During the green tea manufacturing process, evaporation of moisture and PAHs by electric heating were the key factors affecting PAHs residues, which increased from 61.0 μg·kg-1 to 166.1 μg·kg-1 in tea samples. Moreover, PAH residues might evaporate during the spreading and drying processes, which decreased from 292.0 μg·kg-1 to 171.9 μg·kg-1.