近日,華中農(nóng)業(yè)大學園藝林學學院茶學系黃友誼課題組通過H
PLC、HS-SPME-GC-MS和LC-MS/MS等組學手段對紅茶萎凋過程中揮發(fā)性化合物、非揮發(fā)性化合物進行分析檢測,揭示了紅茶萎凋過程中代謝物變化規(guī)律及萎凋工藝對紅茶品質(zhì)形成的貢獻。
茶葉依據(jù)加工工藝與品質(zhì)特征分為六大茶類,萎凋是白茶、烏龍茶和紅茶生產(chǎn)的起始工序。特別是在白茶的生產(chǎn)中,長達48小時的萎凋工藝中,酚類、咖啡堿及游離氨基酸等物質(zhì)會在相關內(nèi)源酶的催化下,通過水解、氧化、縮合及聚合作用,深刻影響揮發(fā)性及非揮發(fā)性化合物。紅茶在世界上六大茶類中消費量最大,但紅茶萎凋過程中揮發(fā)性和非揮發(fā)性化合物的代謝機制尚未探明。
近日,華中農(nóng)業(yè)大學園藝林學學院茶學系黃友誼教授課題組在Food Chemistry發(fā)表了題為“GC–MS and LC-MS/MS metabolomics revealed dynamic changes of volatile and non-volatile compounds during withering process of black tea”的研究論文。該研究采用HS-SPME-GC-MS和LC-MS/MS分別檢測到118 種揮發(fā)性物質(zhì)和648種非揮發(fā)性物質(zhì),通過PCA、PLS-DA、STEM趨勢分析等篩選關鍵代謝物,揭示了紅茶萎凋過程中代謝物的變化規(guī)律。
研究發(fā)現(xiàn),萎凋工藝中發(fā)生了系列水解、分解、萜烯合成和O-甲基化反應,促進了醇、醛、酚、雜環(huán)氧、烴和鹵代烴的積累?;跉馕痘疃戎岛Y選出了47種關鍵揮發(fā)性有機物,發(fā)現(xiàn)萎凋工藝至少涉及12種新關鍵揮發(fā)性有機物的產(chǎn)生,且大部分新的關鍵揮發(fā)性有機物促進了紅茶花香的形成。另外,萎凋工藝產(chǎn)生的新的香氣活性物質(zhì)也與花香、果香、木香呈顯著正相關?;赩IP>1.50、p<0.01篩選出46種非揮發(fā)性特征代謝物,發(fā)現(xiàn)山奈酚、槲皮素、酯型兒茶素和沒食子酸的水解、O-甲基化、縮合和N-?;磻鹆思籽趸S酮、黃酮苷、二氫山奈酚、丁香酸、茶黃素和N-?;岬姆e累。
華中農(nóng)業(yè)大學園藝林學學院博士研究生方欣、碩士畢業(yè)生劉亞楠、碩士研究生肖婧儀為該論文的共同第一作者,黃友誼教授為論文通訊作者。本研究得到了湖北省農(nóng)業(yè)科技創(chuàng)新專項和中央高?;究蒲袠I(yè)務費的資助。
英文摘要:High-performance liquid chromatography (HPLC), headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) and ultra-high performance liquid chromatography–Q-Exactive HF-X mass spectrometer (UHPLC–Q-Exactive HF/MS) were carried out to reveal dynamic changes of volatile and non-volatile compounds during the withering process of black tea. A total of 118 volatile organic compounds (VOCs) and 648 metabolites were identified in fresh and withered tea-leaves, respectively. Among them, 47 VOCs (OAV > 1.0) for the aroma formation, and 46 characteristic metabolites (VIP > 1.50, p < 0.01) selected through orthonormal partial least squares-discriminant analysis, indicated the withering contribution during black tea processing. Overall, the withering promoted alcohols, aldehydes, phenols, heterocyclic oxygen, hydrocarbons and halogenated hydrocarbons through relevant hydrolyzation, decomposition, terpene synthesis, and O-methylation. The hydrolyzation, O-methylation, condensation and N-acylation of kaempferol glycosides, quercetin glycosides, ester catechins, and gallic acid generated the accumulation of methoxyl flavonoids and flavonoid glucosides, dihydrokaempferol, syringic acid, theaflavins, and N-acylated amino acids, respectively.【
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