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基于代谢组学的摊放工艺对春绿绿茶品质代谢物影响

Quality-related Metabolites in Chunlü Green Tea Affected by Varied Withering in Processing

    摘要
  • 摘要:
    目的 探究摊放对新品系春绿加工绿茶过程中品质代谢物的影响，为绿茶品质形成机理奠定基础。
    方法 以春季一芽二叶鲜叶（TL）为原料，按照绿茶加工工艺，设置鲜叶摊放失水率10%（WL-10）与25%（WL-25）两个处理，相应获得两个烘干样（FT-10、FT-25）。运用超高效液相色谱-串联质谱（Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry, UPLC-MS/MS）并结合多元统计方法主成分分析和偏最小二乘判别分析对5组样品进行检测分析。
    结果 代谢组学分析表明，有机酸类化合物差异变化占比最大为39.03%（下调占26.66%，上调占12.37%），其次氨基酸及其衍生物占32.59%（下调占比13.19%，上调占比19.40%），而类黄酮（flavonoids）类物质为15.55%（下调占比8.71%，上调占比6.74%）。进一步分析发现，WL-10与WL-25差异代谢物高达690种（其中下调399种，上调291种），烘干样FT-10（失水率10%）与FT-25（失水率25%）比较发现，差异代谢物为182种（其中下调81种，上调101种）。KEGG富集表明，WL-10与WL-25前10条通路中有色氨酸代谢，苯丙氨酸、酪氨酸和色氨酸代谢，氨基酸合成代谢等，大部分都关于氨基酸、生物碱类、黄酮代谢；FT-10与FT-25差异代谢物仅分布在64条代谢途径中，其中富集前7的有苯丙氨酸代谢、次生代谢物的生物合成等。
    结论 摊放过程中不同程度的失水率对滋味与香气物质的影响很大，适度的摊放可以提升‘春绿’加工绿茶的品质。

     

    Abstract:
    Objective Effect of varied withering during processing on the quality-related metabolites in Chunlü green tea was determined.
    Method Fresh leaves with one bud and two leaves in spring were plucked from Chunlü bushes to make the green tea. Withering the leaves to result in a 10% water loss (WL-10) or 25% water loss (WL-25) was applied in the conventional process to produce 5 sets of finished tea samples, FT-10 and FT-25, respectively, for a metabolomic comparison. Ultra performance liquid chromatography-tandem mass spectrometry was employed for chemical analysis, and multivariate statistical analysis for principal components determination.
    Result Of the differential metabolites between the teas, organic acids constituted the highest proportion that included 26.66% were down-regulated and 12.37% up-regulated. Amino acids and derivatives were second most abundant with 13.19% being down-regulated and 19.40% up-regulated. The third predominant metabolite category was flavonoids that had 8.71% of them down-regulated and 6.74% up-regulated. There were 399 down-regulated and 291 up-regulated metabolites that were different between WL-10 and WL-25. And between FT-10 and FT-25, 81 were down-regulated and 101 up-regulated. The KEGG enrichment analysis on WL-10 and WL-25 showed the top 10 pathways to be associated with tryptophan metabolism, phenylalanine, tyrosine and tryptophan metabolism, amino acid biosynthesis, sesquiterpene and triterpene biosynthesis, etc. Whereas on FT-10 and FT-25, the 182 differential metabolites distributed across 64 metabolic pathways, with 7 most enriched pathways being phenylalanine metabolism, diterpene biosynthesis, biosynthesis of secondary metabolites, and sesquiterpene and triterpene biosynthesis.
    Conclusion The different withering that removed varied amounts of moisture in the leaves produced green teas with significant variations in sensory quality-related metabolites. Identification of these substances and associated metabolic pathways would be of value for process optimization of Chunlü green tea.

     

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