C N H O and mineral element stable isotope ratio analysis for authentication in tea
2020
Liu, Honglin | Zeng, Yitao | Yan, Jingna | Huang, Rui | Zhao, Xin | Zheng, Xiaoling | Mo, Min | Tan, Siyun | Tong, Huarong
In this work, the potential of C, N, H, O and mineral element stable isotope ratios and chemometric methods as a tool to first authenticate Chinese tea according to their blend raw materials was examined. Forty-four multi-elemental stable isotope ratios of four batches of Chongqing tuo tea (n = 27 for each batch) were determined by the EA-IRMS and ICP-MS methods. The clustering results of HCA and PCA were worse than that of PLS-DA, BP-ANN, and LDA. The PLS-DA model displayed good model performance (R²X = 0.57, R²Y = 0.74, and Q² = 0.653). By BP-ANN, the total correct authentication rates for model training and external validation were 100% and 91.2%, respectively. The best performance was obtained by LDA, the total correct authentication rates for model training, cross-validation and external validation were 100%, 100% and 96.9%, respectively. δ²H, δ¹⁸O, ⁹⁸Mo/⁹⁵Mo, ⁹⁶Mo/⁹⁵Mo, and ⁹⁸Mo/⁹⁶Mo were markers for enabling the accurate authentication of Chongqing tuo tea according to formulas. This study has contributed toward generalizing the use of multi-elemental stable isotope ratio fingerprinting as a promising tool for testing the authenticity of tea worldwide.
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