冰葡萄酒酿造过程中特征香气物质的产生及演变机制

Icewine is favored by consumers for its unique aromatic characteristics, thus it has been a popular topic to address by research to understand the chemical background of the production of these volatiles. In recent years, the characteristic volatile compounds have been identified. However, the mechanism of production and development of these compounds during icewine making process is rarely known. Some more characteristic aroma compounds need to be understood. According to our previous research, some compounds that exist in low level with extremely low threshold may contribute to the characteristic aroma profiles of icewine and their chemical structures remain unknown. This project covers the following topics: identify unknown important aromatic components and understand their contribution in the aroma of icewine by utilizing semipreparative-HPLC, olfactometry, GC-qTOF-MS and other modern analytical techniques; analyze the production and development of these volatiles during over-ripening and freezing-thawing process, low temperature fermentation and storage through omics techniques; research into the influence of vinification technical parameters on the production of characteristic volatiles; identify the precursors of key aroma compounds by correlation analysis on omics data and validation experiments. Through all content mentioned above, this project aims to elucidate the mechanism of production and development of key aromatic compounds in icewine. The outcome from this project will not only strengthen the theoretical understanding of the flavor chemistry of wine, but also provide practical guidance to icewine making for consistent and aromatically quantified products.

冰葡萄酒以其独特稀有的香气而深受消费者的喜受，揭示这些特殊香气形成的化学背景一直是冰酒风味化学研究的热点，近年很多特征香气组分已经被鉴定。然而，对冰酒酿造过程这些特征香气的产生及演变规律鲜有报道，尚有一些冰酒的特殊气味组分仍未被认识。我们前期研究发现，贡献冰葡萄酒特征香气的组分包含一些阈值极低且结构未知的痕量物质，本项目拟在此基础上，结合半制备液相、嗅辨仪和气相色谱-高分辨率质谱联用仪等现代分析技术，进一步鉴定冰酒特征香气的未知组分并明确它们的主体贡献；利用组学技术分析果实过熟冻融、低温发酵和陈酿等酿造过程中冰酒特征香气组分产生和演变规律，深入探究工艺条件对特征香气物质形成的影响，基于组学的关联分析筛选关键香气前体物，通过添加实验进行验证，从而阐明冰酒特征香气物质的产生机制及演变规律。研究成果不仅可丰富葡萄酒风味化学的理论体系，而且对于冰葡萄酒呈香稳定和定向酿造均有重要指导意义。

冰葡萄酒以其独特稀有的香气而深受广大消费者的喜爱。本项目揭示了冰葡萄酒酿造过程中特征香气物质的产生及演变机制：（1）通过感官组学分析技术鉴定了‘北冰红’冰红葡萄酒的关键香气物质，并进一步鉴定了冰葡萄酒特征‘甜香’的挥发性组分，揭示了这些香气物质的感官表达机制，发现萜烯、内酯和呋喃酮之间通过相互作用贡献了冰葡萄酒的特征‘甜香’；（2）解析了过熟冻融对冰葡萄酒关键香气物质的影响作用，发现过熟冻融使冰葡萄酒具有更高含量的内酯、挥发性酚、(E)-β-大马士酮、苯乙醛、顺式-氧化玫瑰、双乙酰和肉桂酸乙酯，导致冰葡萄酒的干果味、甜香、蜂蜜香、焦糖香和椰子味更加突出；（3）揭示了葡萄果实过熟冻融影响关键香气物质及其前体物形成的机制，发现葡萄果实的干化失水能够诱发浓缩、厌氧代谢、生物转化、氧化等一系列反应，且反复冻融能够影响上述反应进而引起香气物质的含量发生剧烈变化。通过蛋白质组学分析，进一步证实反复冻融能够影响厌氧代谢和生物转化反应（如脂肪酸降解、萜烯以及苯丙烷生物合成途径），进而影响冰葡萄果实乙醇、高级醇、C6类和丁子香酚等物质的积累；（4）揭示了冰葡萄酒特征香气物质的形成途径，发现过熟冻融促使果实积累大量的糖苷结合态前体物和氧代中间产物（如4-氧代壬酸等），酿造过程中糖苷态前体物的水解使冰葡萄酒具有高含量的里那醇、香叶醇、α-萜品醇、β-香茅醇和橙花醇等萜烯以及(E)-β-大马士酮等降异戊二烯类物质，增强了冰葡萄酒的柑橘、杏/桃、花香、蜂蜜和果干香，而氧代中间产物经酵母转化使冰葡萄酒积累大量的内酯类物质；（5）揭示了带冰压榨的浓缩效应对冰葡萄酒关键香气物质积累的作用。本项目完善了冰葡萄酒的特征香气物质数据库，揭示了冰葡萄酒特征香气物质的产生途径及关键酿造工艺参数的影响机制。研究成果不仅可以丰富冰葡萄酒风味化学的理论体系，而且能够为通过栽培技术和酿造工艺定向改善冰葡萄酒的风味提供理论依据。