凤凰单丛香气及糖苷类香气前体变化研究

Changes of volatile and glycosidically aroma precursors of Fenghuang Dancong

目的测定凤凰单丛加工过程的挥发性香气化合物和糖苷类香气前体的含量变化,并讨论糖苷类香气前体与挥发性香气化合物的含量变化的关系。方法采用溶剂辅助风味蒸发法(solvent assisted flavor evaporation,SAFE)联合气相色谱-质谱联用仪(gas chromatography and mass spectrometry,GC-MS)检测技术分析挥发性物质的变化,再采用衍生法并结合GC-MS定量分析糖苷类香气前体的变化。结果共检测出挥发性香气物质79种,其中包含醇类29种、酯类11种、烯类25种、苯类3种、醛类3种、酮类5种、以及其他化合物3种,以醇类物质的含量最多。在干燥样中,含量最高5种的香气物质为α-法尼烯(24.05%)、橙花叔醇(22.63%)、芳樟醇(11.58%)、吲哚(4.28%)、脱氢芳樟醇(2.95%)。共检测到糖苷类香气前体14种,其中包括6种葡萄糖苷和8种樱草糖苷。其含量在加工过程中都有增加,糖苷类香气前体总量从550.73μg/g增加到843.06μg/g,增加了52.99%。结论糖苷类香气前体的总量相较于鲜叶有明显的增加,对应配基的游离态香气化合物的相对含量没有增加,凤凰单丛香气的形成并非来自于糖苷类香气前体的水解。茶叶中的糖苷类物质有与之相应的前体反应合成糖苷类物质,这个反应一直持续到茶叶加工完成,这也是茶样中糖苷类香气前体在加工过程中持续增加的原因。

Objective To determine the content changes of the volatile substance and the glycosidically aroma precursors during the manufacturing progress and discuss the relationship between them. Methods The changes of volatile substances were analyzed by solvent assisted flavor evaporation （SAFE）, combined with gas chromatography-mass spectrometry （GC-MS）, and the changes of the glycosidically aroma precursors were analyzed by derivatization combined with GC-MS. Results A total of 79 kinds of volatile aroma substance were detected in this product, including 29 kinds of alcohols, 11 kinds of esters, 25 kinds of olefins, 3 kinds of benzenes, 3 kinds of aldehydes, 5 kinds of ketones, and other 3 kinds of compounds, and the content of alcohol was the most. In the dry sample, the highest content of 5 kinds of aroma substances were a-farnesene （24.05%）, nerolidol （22.63%）, linalool （11.58%）, indole （4.28%）, and dehydrolinalool （2.95%）. A total of 14 glycosidically aroma precursors were detected in this product, including 6 kinds of glucosides and 8 kinds of primeverosides. The content of glucoside and primeveroside increased during the processing, and the total amount of glycosidically aroma precursors increased from 550.73 μg/g to 843.06 μg/g, which increased by 52.99%. Conclusion The total amount of glycoside aroma precursors is significantly increased compared with fresh leaves, and the relative content of the corresponding volatile aroma compounds is not increased. The formation of Fenghuang Dancong I aroma does not come from the hydrolysis of glycoside aroma precursors. Glycosidic substances in tea have corresponding precursor reactions to synthesize glycosidic substances, and this reaction continues until the tea processing is completed. This is also the reason why the glycoside aroma precursor in the tea sample continues to increase in the processing process.