Evaluation of Oolong Teas Using ¹H and ¹³C Solid‐state NMR, Sensory Analysis, and Multivariate Statistics

The classification of Wuyi rock tea (Oolong type) is performed by solid‐state nuclear magnetic resonance ( NMR ) for the first time. Quality differences of eight Oolong teas grown in Wuyi Mountains in southeastern China are analyzed by a combination of solid‐state 1 H and 1 H– 13 C CP‐MAS (cross‐polarization magic angle spinning) NMR , partial least‐squares discriminate analysis ( PLS‐DA ), and quantitative descriptive analysis ( QDA ). The contents of caffeine, carbohydrate, polyphenol, and terpenoid were distinguished, and quantification of the metabolites was made based on the 1 H and 13 C MAS spectra. PLS‐DA shows a separation of high‐ and low‐quality Oolong teas, in good agreement with the result of QDA . These results indicate that NMR metabolomic approach enables us to differentiate the analyzed teas based on their chemical composition.