Temporal metabolomics of oolong tea waste degradation reveals a triphasic chemical succession: a foundation for stage-specific valorization

Introduction Each year, millions of tons of nutrient-rich oolong tea processing residue are produced, yet its utilization remains constrained because the residue’s degradation chemistry has not been characterized to date. Existing research commonly considers tea waste as a static feedstock. A metabolomics-informed biorefinery framework is proposed here to synchronize extraction with chemistry tailored to each specific phase. Methods Under carefully regulated mesophilic conditions, oolong tea residue underwent a 35-day aerobic breakdown. Triplicate samples were collected at six time points (Days 0, 3, 7, 14, 28, 35) and analyzed by untargeted UHPLC-Q-Exactive HF-X LC-MS/MS in both positive and negative ion modes, with metabolite annotation at MSI Levels 1–3. The data was analyzed with the use of PCA (Principal Component Analysis), K-means clustering, Differential Abundance Ranking and Correlation Network Analysis. Results The study revealed a deterministic triphasic biochemical succession. In the initial hydrolytic phase (Days 0–7), rapid protein and nucleic acid hydrolysis occurred alongside the release of soluble nitrogenous compounds. In the transitional oxidative phase (Days 7–28), oxidized lipids and phenolic acid derivatives accumulated. In the terminal stabilization phase (Days 28–35), the profile was dominated by simple phenolics and humic-like substances. PCA demonstrated progressive temporal separation (PC1: 51.05% and 51.61% of variance in positive and negative modes). Clustering revealed distinct metabolite trajectories, characterized by an early decline in indicators of fresh tea followed by the later emergence of persistent degradation products. Discussion The degrading phase is intrinsically linked to the value of tea waste. This metabolomic time course offers a chemistry-driven blueprint for precision resource recovery via stage-specific extraction. Extraction, biological activity, agronomic performance, and quantitative sustainability metrics were not assessed; their evaluation is an essential next step.