TECHNISCHE UNIVERSITÄT MÜNCHEN Fakultät für Chemie Lebensmittelchemie Characterization of the Key Aroma Compounds in Raw Toona sinensis (A. Juss.) Roem. Buds and Their Products by Application of the Molecular Sensory Science Concept Xiaoting Zhai Vollständiger Abdruck der von der Fakultät für Chemie der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr.rer.nat.) genehmigten Dissertation. Vorsitzender: Prof. Dr. Michael Rychlik Prüfer der Dissertation: 1. Prof. Dr. Michael Granvogl 2. Prof. Dr. Karl-Heinz Engel Die Dissertation wurde am 21.09.2020 bei der Technischen Universität München eingereicht und durch die Fakultät für Chemie am 12.11.2020 angenommen. Acknowledgments The research work presented in this dissertation was performed in the period from October 2016 to June 2020 under the supervision of Professor Dr. Michael Granvogl at the Technical University of Munich in Freising, Germany. First of all, I would like to express my deepest appreciation to my supervisor Prof. Dr. Michael Granvogl for offering a valuable opportunity to pursue my doctorate research at the Technical University of Munich and also for his wholehearted support in applying for the scholarship. Special thanks for his priceless guidance, encouragement, inspiration, valuable discussions, and suggestions as well as good working conditions during the whole project. I really appreciated his interest in my work and granting me the freedom to explore my imagination in the research. His distinctness, honesty, and patience also had a significant impact on my research and personal life. I would also like to thank him for giving me the opportunity to work in his new group at the University of Hohenheim in Stuttgart, Germany, as a scientific assistant, which broaden my horizons and knowledge by taking care of new colleagues and some instruments. I would like to express my earnest gratitude to the Chinese Scholarship Council (CSC), for its consistent financial support in living expenses during the past four years. Without this scholarship, I wouldn’t be here and could not have a wonderful research experience. I would like to thank Prof. Dr. Karl-Heinz Engel for being the co-examiner of this dissertation, as well as Prof. Dr. Michael Rychlik for accepting the position as chairman in my doctoral examination. I would like to thank all colleagues at the Leibniz Institute for Food Systems Biology and Chair of Food Chemistry and Molecular Sensory Science at Technical University of Munich, for your helpfulness, good cooperation, and participation in numerous sensory tests. In particular, Dr. Johanna Kreißl, Dr. Veronika Mall, Dr. Mario Flaig, Dr. Silva Neiens, Jörg Stein, Nadine Fischer, Philipp Schlumpberger, and Christine Stübner helped me with the introduction, maintenance, and any questions of gas chromatographs and mass spectrometers. I would like to thank Jörg Stein again for his patient support in regard to HPLC and syntheses, which encouraged me a lot. I thank Dr. Stephanie Frank, Dr. Klaas Reglitz, and Ines Otte for always helping me with advice and support about measurements, standards, and GC-MS programs. I also thank Tatsu Sotaro, Kyriaki Antoniadou, Julian Reinhardt, Inge Kirchmann, Sami Kaviani-Nejad, Daniela Füllemann, and Stefanie Fischer. They often had nice conversations with me and shared personal life during lunch and party time, which made me feel I was not lonely in Germany. I would like to express my earnest gratitude to all my lab members from laboratory U.23. I thank Dr. Laura Franitza and Dr. Katrin Matheis who supported me a lot with my experiments at the beginning, e.g., they kindly taught me how to work-up samples, operate SAFE, HRGC-O, and so on. I thank Salam Alghmian who took care of me like her young sister and gave me a lot of tips about my experiments which helped me to understand the measurements and results more clearly. Many thanks to Dr. Carolin Seyfried and Dr. Anja Neugebauer who were always patient in regard to my HRGC-MS measurements and gave me many suggestions. I thank Anneliese Köhler for her technical assistance during my project. I would like to thank Jakob Drees, Carolina Schury, Sabrina Brendel, Valerian Kalb, Florian Utz, Florian Ziegler, and Susanne Wudy for their kindness help and good atmosphere in the laboratory and companionship. I treated them as my second family in Germany. We often discussed our topics, helped each other, and had wonderful leisure time, such as lab-lunch, parties, and trips. Besides, they always took care of me in my personal life, e.g., Carolina and Sabrina often drove me home in the evening, Florian translated the German documents for me and helped me to extend the visa, and they also prepared a nice farewell gift for me which is full of our memories. Special thanks to my Chinese colleagues Dr. Chengdong Zheng, Tiandan Wu, Jinrui Shi, Xingjie Wang, and Dr. Dong Liang in Freising as well as my two Chinese colleagues Yan Zheng and Zhenli Xu in Hohenheim. They made me more comfortable in the institute because of the Chinese communication and same culture. I also thank my Chinese friends who I met in Germany including Li Qiu, Zilu Zhang, Qian Li, Xiao Ma, Dong Li, Dr. Yingyan Mao, Dr. Guangxin Sun, Shuai Zhao, Sufu Gan, and so on. We often had dinner and party, went hiking, traveled to other places together during the weekends and holidays, which enriched my life. We also encouraged and helped each other with living problems. With all of them here, I felt not lonely. At last, I would like to express my deepest gratitude to my family: my parents, my elder sister and her husband, my younger brother and his wife, and my husband, for their endless support, encouragement, and understanding. Especially, many thanks to my sister and brother. Without their good care for our parents in the past years, I couldn’t focus on my doctorate since I was far away from home. Xiaoting Zhai Munich, August 2020 Contents 1 Summary ....................................................................................................................... 1 2 Zusammenfassung ........................................................................................................ 4 3 Abbreviations and common names ............................................................................... 7 4 Introduction ................................................................................................................... 9 4.1 Molecular sensory science concept ............................................................................... 9 4.1.1 Odor-active compounds and aroma perception ..................................................... 9 4.1.2 Molecular sensory science concept / sensomics concept.....................................11 4.2 Toona sinensis (A. Juss.) Roem. (TS) ..........................................................................16 4.2.1 The TS plant ........................................................................................................16 4.2.2 TS economic values .............................................................................................16 4.2.3 TS varieties and the harvest of TS buds ..............................................................17 4.2.4 Composition of TS buds .......................................................................................18 4.2.5 TS buds processing .............................................................................................19 4.2.6 Volatiles of TS buds .............................................................................................20 4.2.7 Aroma-active compounds in TS buds ..................................................................22 5 Objectives ....................................................................................................................24 6 Results and discussion .................................................................................................25 6.1 Characterization of odor-active compounds in raw and blanched TS ...........................25 6.1.1 Screening and identification experiments .............................................................25 6.1.2 Quantitation experiments of fresh TS ...................................................................30 6.1.3 Concentration losses of key odor-active compounds in blanched TS ...................35 6.1.4 Sensorial experiments .........................................................................................36 6.2 Elucidation of the impact of different drying processes on the odorants in TS and commercially dried TS products ...................................................................................38 6.2.1 Screening and identification experiments of differently dried TS ..........................38 6.2.2 Quantitation experiments of differently dried TS ...................................................39 6.2.3 Sensorial experiments of differently dried TS .......................................................41 6.2.4 Characterization of the key odorants in commercially dried TS products..............42 7 References ...................................................................................................................45 8 Appendix ......................................................................................................................54 8.1 Publication 1: Key Odor-Active Compounds in Raw Green and Red Toona sinensis (A. Juss.) Roem. and Their Changes during Blanching ................................................54