灌木与乔木晒青茶生化成分与抗氧化活性研究比较

在灌木茶树留养改造形成乔木茶树的过程中,出现了改造中的灌木茶树、乔木茶树以及改造后的乔木茶树3种类型的茶树。本文对不同季节的上述3类茶树加工的晒青茶叶的生化成分与抗氧化活性进行比较研究。应用分光光度法、高效液相色谱法测定晒青茶的各内含成分含量,发现除苏氨酸、精氨酸和γ-氨基丁酸外,乔木晒青茶的茶氨酸、谷氨酸等15种氨基酸含量与游离氨基酸总量均高于灌木晒青茶（P<0.05）,而乔木晒青茶的茶多酚、没食子酸、1,4,6-O-没食子酰基-β-D-葡萄糖、表没食子儿茶素没食子酸酯（EGCG）的含量显著低于灌木晒青茶（P<0.05）,感官审评表明灌木晒青茶滋味较乔木晒青茶苦涩;正交偏最小二乘法（OPLS-DA）分析表明,两类茶聚成不同簇,进一步证实了茶叶生化成分存在差异。春季样品中,除羟自由基清除能力无显著差异外,乔木晒青茶的总抗氧化能力、DPPH自由基和超氧阴离子清除能力均显著高于灌木晒青茶（P<0.05）;秋季样品中,乔木晒青茶的总抗氧化能力显著高于灌木晒青茶（P<0.05）,但乔木晒青茶的超氧阴离子清除率则显著低于灌木晒青茶（P<0.05）,而DPPH和羟自由基清除活性二者差异不显著（P>0.05）。综上,与灌木晒青茶比较,改造形成的乔木晒青茶的氨基酸含量提高,多酚含量降低,苦涩度降低,部分抗氧化活性指标提高,表明灌木茶树留养改造成乔木茶树,能够提高晒青茶品质。

Comparison of Biochemical Components and Antioxidant Activities among Sun-dried Green Tea Produced by Fresh Leaves of Bush and Arbor Tree

Bush, transforming and transformed arbor tea trees would be formed during the transformation of tea plantation from bush to arbor trees. In this study, the biochemical components and antioxidant activities of sun-dried green tea processed by the above three kinds of tea plants were compared. The contents of various components were determined by spectrophotometry and high performance liquid chromatography methods. The content of theanine, glutamic acid and other 15 amino acids in arbor tea were higher than those in bush tea, exception threonine, arginine and gamma-aminobutyric acid (P<0.05), while the content of tea polyphenols, gallic acid, 1,4,6-O-gallic acyl-beta- D-glucose and epigallocatechin gallate (EGCG) in arbor tea were significantly lower than those in bush tea (P<0.05). Sensory evaluation showed that the taste of bush tea was bitterer than that of arbor tea. Arbor and bush tea grouped into different clusters in orthogonal partial least squares analysis of the content of the compounds, which confirmed the difference of the biochemical components between these two teas. The activities of spring arbor tea including the total antioxidant capacity, DPPH free radical and superoxide anion scavenging capacity were higher than those of bush tea (P<0.05), while hydroxyl radical scavenging abilities between these two types of teas were not different. In autumn tea, the total antioxidant capacity of arbor tea was higher than that of bush tea (P<0.05), while the scavenging capacity of superoxide anion were lower than bush tea (P<0.05), while the scavenging capacities of hydroxyl free radical and DPPH were not different (P>0.05). In summary, comparison to bush sun-dried green tea, the content of amino acid in arbor tea was increased, and the level of polyphenol and bitterness were reduced. Partial antioxidant activities were also increased. Thus, the transformation of tea plantation from bush to arbor tree can improve the quality of sun-dried green tea.