【摘要】 为探明白茶加工过程中糖苷类香气成分的代谢变化,本试验采用顶空固相微萃取/气相色谱-质谱联用法测定了糖苷类香气成分的含量;通过转录组测序分析了β-樱草糖苷酶及28条β-葡萄糖苷酶基因表达量,并进行qRT-PCR验证;采用对硝基苯酚显色法检测β-葡萄糖苷酶活性。结果表明芳樟醇、香叶醇、苯乙醇、苯甲醛、水杨酸甲酯在白茶加工过程中显著增加。在茶鲜叶萎凋减重≤20%阶段,β-樱草糖苷酶基因表达量降低,随后维持稳定;11条β-葡萄糖苷酶基因呈持续下调表达趋势,3条β-葡萄糖苷酶基因呈现上调表达趋势。在茶鲜叶萎凋减重≤30%阶段,β-葡萄糖苷酶活性提高,随后无明显变化。因此,根据糖苷类香气成分的形成途径推测樱草糖苷酶解作用对这些香气形成贡献较小。而CsGH1BG6和CsGH1BG21的表达对香叶醇和芳樟醇的积累略有贡献。更多还原

【Abstract】 Metabolism of aromatic glycosides in white tea undergoes changes during processing. The chemical changes were analyzed using the headspace solid phase microextraction(HS-SPME)/gas chromatography-mass spectrometry(GC-MS). Expressions of the β-primeverosidase and 28 β-glucosidase genes were determined by transcriptome sequencing and verified by qRT-PCR. And, the enzymatic activity of β-glucosidase was detected by p-nitrophenol colorimetry. The results showed that linalool, geraniol, phenylethanol, benzaldehyde, and methyl salicylate increased significantly in the white tea as it was processed. The expression of β-primeverosidase gene was down-regulated at withering stage when the weight loss of fresh leaves was ≤20% and followed by a steady state afterward. Meanwhile, 11 β-glucosidase genes continuously down-regulated, and 3 up-regulated. When the leaf weight loss was less than 30%, the β-glucosidase activity increased but remained constant as the withering process continued. According to the formation pathway of glycoside aroma components, it appeared that the enzymatic hydrolysis of primeveroside had little contribution to the formation of these aroma components. On the other hand, CsGH1 BG6 and CsGH1 BG21 were found related to the formation of geraniol and linalool.更多还原