Quality Analysis of Baoqing Guiding Green Tea Based on Principal Component and Cluster Analysis

In order to explore the quality of Baoqing guiding green tea and establish its evaluation system, 30 samples of Baoqing guiding green tea were selected to evaluate the sensory quality, and the contents of biochemical components such as water extract, tea polyphenols, caffeine, amino acids and soluble sugar and catechin composition were determined. At the same time, the quality of Baoqing guiding green tea was comprehensively evaluated by principal component analysis (PCA) and cluster analysis (CA), and the quality evaluation model of Baoqing guiding green tea was established. The results showed that the sensory of spring tea was the best, summer tea was the second, and autumn tea was the worst. The water extract content of Baoqing guiding green tea was 44.77%~49.17%, the content of tea polyphenols was 22.49%~26.84%, the content of caffeine was 4.89%~5.93%, the content of amino acids was 2.88%~5.84%, and the content of soluble sugar was 4.16%~7.02%, which showed the characteristics of high amino acid, high caffeine and high EGCG, and accorded with the biochemical characteristics of famous green tea. There was a very significant correlation between the contents of biochemical components of Baoqing guiding green tea at different picking stages, of which water extract, tea polyphenol, caffeine, D-LC, EC and GCG were significantly correlated (P<0.01), while tea polyphenol, caffeine and soluble sugar were significantly correlated (P<0.05). Three principal components were extracted by PCA and the cumulative variance contribution rate was 89.869%, and the comprehensive quality evaluation model of Baoqing guiding green tea was established as F=0.543F₁+0.310F₂+0.046F₃. According to result of CA, amino acids, soluble sugar, EGCG and ECG should be taken and the main basis for classification of Baoqing guiding green tea. Baoqing green tea could be divided into 2 groups and 4 subgroups and its comprehensive quality decreased gradually according to the collecting time. This study could provide a reasonable and quantifiable evaluation method for tea quality. The biochemical characteristics of Baoqing guiding tea were revealed, a feasible quality evaluation model was established, and the key quality indexes were determined in this study, which would provide theoretical basis for the variety breeding, development and utilization of Baoqing guiding tea resources.