Metabolomics based on UHPLC-Orbitrap-MS and GNPS 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 to 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 early stage but started to differentiate from each other at the 5th and the 7th year in wet-hot and dry-cold environment. 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 multi-libraries matching and SIRIUS calculation. The metabolomic data were consistent with...