炒青绿茶干燥过程中氮氧杂环类化合物的衍变规律及形成机制研究

Tea aroma is one of the crucial factors for evaluation the quality of roasted green tea. N,O-heterocycles play an important role in the characteristic flavor of roasted green tea due to the powerful strong odours and low odour thresholds. However, studies on N,O-heterocycles in roasted green tea are very limited by far. The dynamic changes during the drying process remain unclear. Furthermore, studies on the key precursor species and the formation mechanism of N,O-heterocycles have not been reported yet, which restrict the development of quality control and directional processing technology of roasted green tea. In our previous work, we have already established and characterized the pyrazines by using infrared-assisted headspace solid-phase microextraction coupling with gas chromatography-triple quadrupole tandem mass spectrometry, which prove the practical feasibility. Based on this, we intend to further explore the chemical compositions and analytical methods of N,O-heterocycles, and investigate the dynamic changes of N,O-heterocycles during the drying process, as well as unravel the key precursors for aroma formation. Furthermore, model systems of Maillard reaction will be analyzed by stable isotope tracer technique to clarify the formation mechanism. The results will not only enrich the theoretical basis of tea aroma quality quantitatively, but also provide technical support for the precise aroma manipulation and manufacturing of roasted green tea.

香气是反映炒青绿茶品质的重要指标之一。氮氧杂环类化合物香气特征突出，香味阈值低，对炒青绿茶特征品质的形成具有重要贡献。然而，目前关于炒青绿茶中氮氧杂环类化合物的系统研究较为匮乏，其在干燥过程中的衍变规律尚不明晰，其形成的关键前体物质和形成机制还有待挖掘，限制了炒青绿茶品质调控和定向加工技术的发展。在前期工作中，申请人已建立了基于红外辅助顶空固相微萃取结合气相色谱-三重四极杆串联质谱技术针对炒青绿茶中吡嗪类化合物的分析方法，证明了该方法的切实可行性。本研究拟在此基础上进一步拓展，探索氮氧杂环类化合物的化学组成及分析方法，阐明干燥过程中氮氧杂环类化合物的动态衍变规律，揭示氮氧杂环类化合物形成的关键前体物质，在此基础上进一步采用稳定同位素示踪技术分析模拟Maillard体系，探究其生成机制。研究结果不仅可以充实茶叶香气品质量化理论研究，而且能够为炒青绿茶优质香型的精准调控、定向加工提供技术支撑。

香气是反映炒青绿茶品质的重要指标之一。氮氧杂环类化合物香气特征突出，香味阈值低，对炒青绿茶特征品质的形成具有重要贡献。然而，目前关于炒青绿茶中氮氧杂环类化合物的系统研究较为匮乏，其在干燥过程中的衍变规律尚不明晰，其形成的关键前体物质和形成机制还有待挖掘，限制了炒青绿茶品质调控和定向加工技术的发展。基于此，本研究首次建立了基于箭形固相微萃取技术结合气相色谱-三重四极杆串联质谱技术快速、精准定量绿茶中氮氧杂环类化合物的方法；明确了干燥方式、干燥时长和温度对氮氧杂环类化合物的影响机制，糠醛可作为评估干燥程度的重要指标化合物，干燥时长25min和40min是氮氧杂环类化合物变化最剧烈的转折点；筛选出脯氨酸为氮氧杂环类化合物生成的关键前体物质，并通过美拉德模拟体系，进一步明晰了氮氧杂环类化合物生成路径和机制。研究结果不仅充实了茶叶香气品质量化理论研究，而且为炒青绿茶优质香型的精准调控、定向加工提供了理论支撑。依托本项目，发表SCI论文4篇，申请发明专利2项（授权发明专利2项，其中1项已转化许可），协助培养硕士研究生1名，对照基金任务书，已全面完成考核指标。