Microbial action and moist-heat action are crucial factors that influence the piling fermentation (PF) of Pu-erh tea. However, their effects on the quality of Pu-erh tea remain unclear. In this study, the effects of spontaneous PF (SPPF) and sterile PF (STPF) on the chemical profile of Pu-erh tea were investigated for the first time, and sun-dried green tea was used as a raw material to determine the factors contributing to the unique quality of Pu-erh tea. The results indicated that the SPPF-processed samples had a stale and mellow taste, whereas the STPF-processed samples had a sweet and mellow taste. Through metabolomics-based analysis, 21 potential markers of microbial action (including kaempferol, quercetin, and dulcitol) and 10 potential markers of moist-heat action (including ellagic acid, β-glucogallin, and ascorbic acid) were screened among 186 differential metabolites. Correlation analysis with taste revealed that metabolites upregulated by moist-heat and microbial action were the main factors contributing to the staler mellow taste of the SPPF-processed samples and the sweeter mellow taste of the STPF-processed samples. Kaempferol, quercetin, and ellagic acid were the main active substances formed under microbial action. This study provides new knowledge regarding the quality formation mechanism of Pu-erh tea.

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代谢组学揭示微生物作用和湿热作用对普洱茶非挥发性成分的影响

微生物作用和湿热作用是影响普洱茶堆积发酵(PF)的关键因素。然而，它们对普洱茶品质的影响尚不清楚。本研究首次考察了自发PF（SPPF）和灭菌PF（STPF）对普洱茶化学特性的影响，并以晒干绿茶为原料，确定了影响因素。造就了普洱茶的独特品质。结果表明，经 SPPF 处理的样品具有陈旧和醇厚的味道，而经 STPF 处理的样品具有甜味和醇厚的味道。通过基于代谢组学的分析，21 种微生物作用的潜在标志物（包括山柰酚、槲皮素和半乳糖醇）和 10 种湿热作用的潜在标志物（包括鞣花酸、β-葡萄糖没食子素、和抗坏血酸）在 186 种差异代谢物中进行了筛选。与味觉的相关性分析表明，湿热和微生物作用上调的代谢物是导致SPPF处理样品口感更醇厚和STPF处理样品口感更甜醇的主要因素。山柰酚、槲皮素和鞣花酸是微生物作用下形成的主要活性物质。本研究为普洱茶品质形成机制提供了新的认识。和鞣花酸是在微生物作用下形成的主要活性物质。本研究为普洱茶品质形成机制提供了新的认识。和鞣花酸是在微生物作用下形成的主要活性物质。本研究为普洱茶品质形成机制提供了新的认识。