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

Abstract

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 1H and 1H– 13C 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 1H and 13C 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.

Characterization of Key Aroma-Active Compounds in Rough and Moderate Fire Rougui Wuyi Rock Tea (Camellia sinensis) by Sensory-Directed Flavor Analysis and Elucidation of the Influences of Roasting on Aroma

“…Volatiles in teas are only present in minimum quantities of 0.01% of total dry weight, but the aroma still affects the acceptance of a tea before it is tasted . The Rougui WRT is distinguished by the strong aroma, especially the cinnamon-like odor, which is the reason why it is called Rougui (=cassia) .…”

Metabolite Profiling of 14 Wuyi Rock Tea Cultivars Using UPLC-QTOF MS and UPLC-QqQ MS Combined with Chemometrics

“…On the other hand, the choice of cultivars to produce Wuyi Rock tea also matters but remains underexplored except for a few comparative studies, which have focused only on a small number of major constituents in processed tea and were not performed under controlled environmental conditions [ 8 , 9 ]. Contributed by unique climate and soil conditions, Wuyi Mountain is home to a large collection of tea germplasms.…”

Differences of Typical Wuyi Rock Tea in Taste and Nonvolatiles Profile Revealed by Multisensory Analysis and LC–MS-Based Metabolomics

“…Nevertheless, the salty and umami tastes of Shuixian were stronger than those of Rougui. Cai et al also found that Rougui is bitterer than Shuixian, comparing 8 Wuyi rock tea through 1 H and 13 C solid-state NMR and QDA. In Shuixian samples, S3, S8, S18, and S24 were similar in taste profile, except for S6 (Figure C).…”