Metabolomics Based on UHPLC-Orbitrap-MS and Global Natural Product Social Molecular Networking Reveals Effects of Time Scale and Environment of Storage on the Metabolites and Taste Quality of Raw Pu-erh Tea

Raw
Pu-erh tea (RPT) needs ageing before drinking. However, the
influence from environment and time of storage on chemical profile
and flavor of RPT is unclear. In this study, the RPTs stored in wet-hot
or dry-cold environment for 1–9 years were assessed using metabolomics
based on UHPLC-Orbitrap-MS and global natural product social (GNPS)
feature-based molecular networking as well as electronic tongue measurement.
The results exhibited that the chemical profiles of RPTs were similar
at an early stage but started to differentiate from each other at
the 5th and the 7th year in wet-hot and dry-cold environments. The
discriminating features including N-ethyl-2-pyrrolidinone-substituted
flavan-3-ols (flavoalkaloids), unsaturated fatty acids, lysophosphatidylcholines,
flavan-3-ols, amino acids, and flavonol-O-glycosides
among the three chemical profiles were discovered and analyzed by
means of multivariate statistics, GNPS multilibraries matching, and
SIRIUS calculation. The metabolomic data were consistent with the
results obtained through electronic tongue measurement.