武夷岩茶炭焙工艺对肉桂乌龙茶挥发性组分的影响

以武夷岩茶当家茶树品种肉桂(Camellia sinensis ‘Rougui’)鲜叶制成的乌龙茶为试材，基于顶空固相微萃取法(HS-SPME)结合气相色谱-质谱联用技术(GC-MS)，探讨武夷岩茶炭焙工艺对肉桂乌龙茶挥发性组分的影响。实验中共检测到样本挥发性成分443个，其中包括96个杂环化合物、81个酯类化合物、31个萜类化合物、42个芳香烃类化合物、55个酮类化合物、24个其他烃类化合物、35个醇类化合物、24个醛类化合物、15个酚类化合物、14个胺类化合物、10个酸类化合物、5个含氮化合物、3个含硫化合物等。经主成分分析及聚类分析显示，焙火工艺是影响乌龙茶挥发性成分含量的重要影响因子。随炭焙程度增加，不同类别物质中的多数挥发性成分含量随之显著升高，且以美拉德反应产物等具有茶叶烘炒香的吡嗪类、糠醛类衍生物、吡咯类等化合物最具代表性；同时，部分含量丰富且具有乌龙茶特殊花果香气的醇类、萜烯类物质如香叶醇、反式-橙花叔醇、植物醇、α-法尼烯等，及具清新花香的吲哚含量显著降低。然而，大多数挥发性差异代谢物随炭焙程度增加相对含量显著升高，并不代表茶叶中芳香物质总量增加。研究表明，乌龙茶精制烘焙过程中，香气物质的积累主要来自热作用下的美拉德反应及非酶促的降解和氧化，如黄酮苷类物质水解。

Effects of Wuyi Charcoal Baking Process on the Volatile Components of Rougui Oolong Tea

Based on head-space solid phase microextraction / gas chromatography-mass spectrometry (HS-SPME/ GC-MS), oolong tea made from the fresh leaves of a predominant cultivar of Wuyi rock tea, Camellia sinensis ‘Rougui’, was chosen to investigate the effects of Wuyi charcoal baking process on the volatile components of Rougui oolong tea. A total of 443 volatile metabolites were identified, including 96 heterocyclic compounds, 81 ester compounds, 31 terpenoids compounds, 42 aromatics compounds, 55 ketone compounds, 24 hydrocarbons compounds, 35 alcohol compounds, 24 aldehyde compounds, 15 phenol compounds, 14 amine compounds, 10 acid compounds, 5 nitrogen compounds, 3 sulfur compounds and others. According to these 443 metabolites, both principal component analysis (PCA) and hierarchical clustering analysis (HCA) were demonstrated, which indicated that baking process was a key factor affecting the content of volatile components in oolong tea. With the increasing of charcoal baking degree, the contents of most volatile components in different substance classification increased significantly, and the represented components were the products with the baked aroma such as pyrazines, furfural derivatives and furan, which were generated by chemical reaction under thermal treatments like Maillard; Meanwhile, some substances with rich content and special floral and fruit aroma in oolong tea like geraniol, trans-nerolidol, phytol, α-farnesene and indole reduced significantly. The relative content of most volatile components increased significantly with the increasing of the charcoal baking degree, still cannot mean that the increasing in the total amount of aromatic substances in tea. Our research illustrated that the accumulation of aroma substances in oolong tea during the refined baking process mainly comes from the Maillard reaction under thermal treatments, and non-enzymatic degradation and oxidation like glycosides hydrolysis.