JUSTUS LIEBIG UNIVERSITY GIESSEN Institute for Phytopathology HOCHSCHULE GEISENHEIM UNIVERSITY Department of Microbiology and Biochemistry Impact of specific volatile thiols on varietal aroma of wines produced from Greek and some international grape varieties Thesis submitted in partial fulfilment of the requirements for the degree of Doctor agriculturae (Dr. agr.) in the Faculty of Agricultural Sciences, Nutritional Sciences and Environmental Management at the Justus Liebig University Giessen Submitted by Andreas Kapaklis, M.Sc. Born in Kalamata/Greece Giessen, 2014 This Ph.D. work was approved by the committee (Faculty 09: Agricultural Sciences, Nutritional Sciences and Environmental Management) of Justus Liebig University Giessen, as a thesis to award the Doctor degree of agriculturae (Dr. agr.) 1st Supervisor: Prof. Dr. Karl-Heinz Kogel, Justus Liebig University Giessen 2nd Supervisor: Prof. Dr. Doris Rauhut, Hochschule Geisenheim University Examiner: Prof. Dr. Sylvia Schnell, Justus Liebig University Giessen Examiner: Prof. Dr. Bernd Honermeier, Justus Liebig University Giessen Chairwoman: Prof. Dr. Gertrud Morlock, Justus Liebig University Giessen Date of defense: 2nd November 2015 2 Abstract The volatile composition of young white wines from Greek, Swiss and German autochthonous varieties but also of the international variety Sauvignon blanc were studied using gas chromatography and other analytical techniques. The composition of the volatile constituents of the Greek varieties Malagousia, Asyrtiko and Roditis with special attention on varietal thiols was investigated. An analytical method was adapted and validated for their quantification. Wines of the Greek grape varieties, especially Malagousia, were proved to be rich in varietal thiols for the first time. Concentrations of up to 44.7 ng/L 4MSP (4-methyl-4-sulfanylpentan-2-one) and 1942 ng/L for 3SH (3-sulfanylhexan-1-ol) were measured, which are far above their odour threshold. Furthermore, the wines obtained from Malagousia showed high concentrations of monoterpenes (linalool, α-terpineol, hotrienol and geraniol) and C13 norisoprenoids (β-damascenone). In addition a scheme is proposed for the characterisation of wines from unknown grape varieties with focus on varietal thiols and other aromatic compounds. The characterisation scheme was developed using international and autochthonous varieties. Zusammenfassung Die Zusammensetzung von Aromakomponenten in Jungweinen von griechischen, Schweizer und deutschen autochthonen Rebsorten, sowie aus der internationalen Rebsorte Sauvignon blanc, wurden untersucht. Hierzu wurden gaschromatographische und andere analytische Verfahren eingesetzt. Für diese Studie wurden flüchtige Bestandteile der griechischen Rebsorten Malagousia, Asyrtiko und Roditis unter besonderer Berücksichtigung der rebsortentypischen Thiole gemessen. Für deren Quantifizierung wurde eine analytische Methode modifiziert und validiert. In den Weinen der griechischen Rebsorten, insbesondere Malagousia, wurden hohe Konzentrationen der rebsortentypischen Thiole zum ersten Mal festgestellt. Die gemessen Konzentrationen bis 44.7 ng/L 4MSP (4-Methyl-4-sulfanylpentan-2-on) und 1942 ng/L 3SH (3-Sulfanylhexan-1-ol) liegen weit über ihrem Geruchsschwellenwert. In den Proben von Malagousia wurden hohe Konzentrationen an Monoterpenen (Linalool, α-Terpineol, Hotrienol und Geraniol) und C13 Norisoprenoiden (β-Damascenone) nachgewiesen. Für die Charakterisierung von unbekannten Rebsorten wurde ein Schema mit Fokus auf die rebsortentypischen Thiole und andere Aromastoffe entwickelt. Zur Entwicklung dieses Schemas wurden internationale und autochthone Rebsorten verwendet. 3 Acknowledgements Prof. Dr. Karl-Heinz Kogel, Institute for Phytopathology, Research Center for Biosystems, Land Use and Nutrition (IFZ), Justus Liebig University of Giessen, who acted as my supervisor and provided me support especially in the critical moments of this work and the help for sorting everything out. Prof. Dr. Doris Rauhut, Department of Microbiology and Biochemistry, Hochschule Geisenheim University, who acted as my second supervisor and supported me all these years for completing my work. Her help was crucial in difficult moments. Dr. Claus-Dieter Patz, Department of Wine Chemistry & Beverage Research, Hochschule Geisenheim University, for all the support and guidance for the statistical analysis part. Anja Giehl of the same department for the FTIR analysis. Prof. Dr. Rainer Jung and Christoph Schüssler, Department of Enology, Modeling & Systems Analysis, Hochschule Geisenheim University for helping me with all the sensory analysis. I would like to thank all the staff members from the Department of Microbiology and Biochemistry of the Hochschule Geisenheim University for their assistance during all these years. I would like to thank especially the people that helped me with the analysis: Beata Beisert (low boiling point sulphur compounds and support in measuring varietal thiols), Heike Semmler (organic acids & sugars), Stefanie Fritsch and Kristin Ebert (‘Kaltron’ & analysis of terpenes). Anja Abd Elrehim for her help in getting my English sorted out! Special thanks to the wonderful person Helmut Kürbel…without his support I probably would not have come so far. You will always be remembered! For my colleagues Pat, Armin, Jochen and Marco for having some good chats, for their help and support. For chief enologist Hansueli Pfenniger of the winery Robert Gilliard SA in Sion, Switzerland when I called him up for wines he immediately helped me out. For my Greek fellow enologist Anestis Haitidis for helping me out with the wonders of the Greek vineyard. To my friends Volker Schaefer and Aysha Kolmer that put up with me for all these years, for Marco Lazzarino that gave me a good input in statistics, for Jasmin Schuler that helped me with the formatting of the text, Simos Karagiannidis for taking a critical look in the last minute, Loredana Gentile and Karin Hürlimann-Künzle that helped me out with my German….thank you all! ….for my better half Katerina who even in the difficult times was always listening and supporting me. I cannot express my gratitude to her in words. 4 Table of contents Abstract .................................................................................................................................................... 3 Zusammenfassung .................................................................................................................................. 3 Acknowledgements ................................................................................................................................. 4 List of figures ........................................................................................................................................... 9 List of tables........................................................................................................................................... 13 Abbreviations ......................................................................................................................................... 14 General introduction .............................................................................................................................. 16 1. Literature review ........................................................................................................................... 17 1.1 Introduction ............................................................................................................................ 17 1.2 Wine aroma ........................................................................................................................... 17 1.3 Varietal aroma ....................................................................................................................... 18 1.3.1 Terpenes ............................................................................................................................ 19 1.3.1.1 Monoterpenes .................................................................................................................... 19 1.3.1.2 C13 Norisoprenoid derivatives ............................................................................................ 20 1.3.2 Methoxypyrazines .............................................................................................................. 20 1.3.3 Varietal thiols ..................................................................................................................... 21 1.3.3.1 Biogenesis of varietal thiols ............................................................................................... 22 1.3.3.2 Factors affecting the release of varietal thiols ................................................................... 23 1.3.3.3 4-Methyl-4-sulfanylpentan-2-one (4MSP) ......................................................................... 24 1.3.3.4 3-Sulfanyl-hexyl acetate (3SHA) ....................................................................................... 24 1.3.3.5 3-Sulfanylhexan-1-ol (3SH) ............................................................................................... 25 1.4 Quantification of varietal thiols ............................................................................................... 26 1.4.1 Extraction of thiols with agarose gel containing phenylmercuric ions ............................... 26 1.4.2 The use of p-HMB in combination with DOWEX basic anion exchange columns ............ 28 1.4.3 Alternative
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