Multi-element stable isotope analysis of alkylpyrazines and pyridine from roast coffee [Elektronische Ressource] / vorgelegt von Christina Preston

Maurice Preston

Informations

• Publié par: julius-maximilians-universitat_wurzburg
• Publié le: 01 janvier 2009
• Nombre de lectures: 77
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Multi-element Stable Isotope Analysis of Alkylpyrazines
and Pyridine from Roast Coffee








Dissertation zur Erlangung des
naturwissenschaftlichen Doktorgrades
der Julius-Maximilians-Universität Würzburg










vorgelegt von
Christina Preston
aus Aalen


Würzburg 2008





















Eingereicht am: 26. September 2008
bei der Fakultät für Chemie und Pharmazie


1. Gutachter: Prof. Dr. P. Schreier
2. Gutachter: Prof. Dr. H.-U. Humpf
der Dissertation


1. Prüfer: Prof. Dr. P. Schreier
2. Prüfer: Prof. Dr. H.-U. Humpf
3. Prüfer: Prof. Dr. C. Sotriffer
des öffentlichen Promotionskolloquiums


Tag des öffentlichen Promotionskolloquiums: 21. Januar 2009

Doktorurkunde ausgehändigt am: ………………………………


Acknowledgements

The following research was conducted at the chair of food chemistry, University
of Würzburg, from January 2004 to May 2007, under the guidance of Professor
Dr. Peter Schreier.

Professor Dr. Peter Schreier I thank for the isotopic-topic, the scientific support,
the interesting discussions, not always strictly work-related, and the freedom of
researching independently.

Furthermore, I thank Dr. Thorsten König, from Givaudan (formerly Quest Inter-
national), for providing samples and Dr. Elke Richling, Dr. Dominique Kavvadias,
as well as the student workers Christopher Heppel and Silvia Hummel, for the
pre-work conducted on this research topic.

Special thanks go to the ‘F-Praktikanten’ Kathrin Kahle, Helena Bader, Stefanie
Kohlhepp, Ina Kleinsteuber, Magdalena Müller, Karin Thomas, Christof Madinger
and Tanja Welsch as well as to the ‘C-Praktikanten’ Daniela Trost and Fabian
Oberle, who all supported me courageously during their advanced practical
courses. They all contributed substantially to the success of this work, with their
never-tiring energy, their good ideas and friendly relationships.

Dr. Frank Heckel and Dr. Sandra Elß divulged their GC-MS knowledge to me and
taught me all they could about these machines. I thank them and Michael Kempf,
both for the good working relationship between us in the GC-MS department and
for their willingness to help out with the ‘special’ problems of the IRMS.

Eva-Maria Rumpel successfully gave me a three-month crash course in IRMS
measurement, whilst Dr. Markus Appel contributed his extensive knowledge on
the IRMS. With Dr. Sandra Elß’s assistance the work with the machine was highly
productive and always exciting. I thank the IRMS team for their help in the often
eventful and seemingly never-ending work, and without whom stable isotopes
would still be a mystery to us all.

A very special thank you goes to Theresia Feuerbach, who took loads of work off
my shoulders, by conducting the practical work for other projects and helping
out, whenever she could.

I thank my laboratory colleagues, Dr. Markus Appel, Theresia Feuerbach and
Michael Kempf, for sharing rooms and laboratory benches with me, even if it was
sometimes hard to find space for working.
For interpreting NMR results I had help from Dr. Markus Appel and Sanja Locher
and for the work on the HPLC’s I thank the ‘cellar kids’ Kathrin Kahle, Wolfgang
Hümmer and Matthias Ackermann.

Of the non Food Chemists, Doris Moret gave invaluable pharmaceutical technical
help and the workshop crew Matthias, Karl and especially Schorsch, were
indispensable for all kinds of repairs and constructions. I will, furthermore, miss
the ‘Technischer Betrieb’ with Andi, Pierre, Thomas and of course ‘Herr Fritz’ and
thank them, particularly, for the lovely midday breaks we girls were invited to.

Otherwise, my never-ending thanks go to our working group, for all the good
times, excursions, feasts and friendships we enjoyed together. Here, I would
especially like to thank Dr. Sandra Elß and Kathrin Kahle for their friendship and
our ‘girls - pizza - ice cream - evenings’, as well as Matthias Ackermann and
Wolfgang Hümmer, who both participated in the friendship and sometimes in the
evenings, if not always voluntarily for Wolfgang. Thank you also to everyone,
who had to endure my questions and corrections to this piece of work, especially
my father, who is now probably proficient enough to referate on stable isotope
analysis off-by-heart.

My thanks also go to the F.R.U.I.T. Foundation, Heidelberg, Unibund and the
program ‘Chancengleichheit für Frauen in Forschung und Lehre’ from the
University of Würzburg for their financial support.

My main thanks go to my parents and my sister, who always let me do what I
thought best, and supported me on my way with all means, as well as to my
friend, Kathrin Diegelmann, whose friendship always meant a lot to me, and
without whom, studying would have only been half as much fun and not as
successful.




































‘Theory is, when one knows everything, but nothing works,
Praxis is, when everything works, but no-one knows why.
For us theory and praxis are combined:
Nothing works and no-one knows why!’

- Unknown







Index I

Index
Publications........................................................................................... VI
Explanations and Abbreviations ............................................................ IX
Summary..............................................................................................XII
Zusammenfassung ................................................................................XV
1 Introduction......................................................................................1
2 State of Knowledge ...........................................................................3
2.1 Sources, Distribution and Fractionation of Isotopes............................ 3
2.2 Isotope Fractionation of Hydrogen................................................... 6
2.2.1 Thermodynamic Isotope Fractionation.......................................... 6
2.2.2 Isotope fractionation in plants..................................................... 8
2.3 Isotope Fractionation of Carbon .................................................... 10
2.3.1 Thermodynamic Isotope Fractionation........................................ 10
2.3.2 Isotope Fractionation in Plants .................................................. 11
2.4 Isotope Fractionation of Nitrogen 14
2.4.1 Thermodynamic Isotope Fractionation. 14
2.4.2 Isotope Fractionation in Plants 16
2.5 Methods and Applications of Stable Isotope Analysis in Food Chemistry ..
................................................................................................ 19
2.5.1 Site-Specific Natural Isotope Fractionation – Nuclear Magnetic
®Resonance (SNIF – NMR ) ....................................................... 19
2.5.2 Isotope Ratio Mass Spectrometry (IRMS).................................... 20
2.5.2.1 Elemental Analyser – Isotope Ratio Mass Spectrometer (EA-IRMS)
....................................................................................... 22
2.5.2.1.1 Elemental Analyser – Combustion – Isotope Ratio Mass
Spectrometry (EA–C–IRMS) ........................................... 22
2.5.2.1.2 Elemental Analyser – Pyrolysis – Isotope Ratio Mass
Spectrometry (EA–P–IRMS) ........................................ 23
2.5.2.2 Gas Chromatography – Isotope Ratio Mass Spectrometry (GC-
IRMS) .............................................................................. 25
2.5.2.2.1 Gas Chromatography – Combustion – Isotope Ratio Mass
Spectrometry (GC – C – IRMS)....................................... 26 II Index

2.5.2.2.2 Gas Chromatography – Pyrolysis – Isotope Ratio Mass
Spectrometry (GC – P – IRMS) ....................................... 27
2.5.3 Application of Stable Isotope Analysis ........................................ 27
2.5.3.1 Authenticity Assessment of Aroma Compounds....................... 28
2.5.3.2 Further Applications...........................................................30
2.6 Coffee and Coffee Aroma ............................................................. 31
2.6.1 History and Importance of Coffee .............................................. 31
2.6.2 Botanic and Production Types ................................................... 32
2.6.3 Composition of Green Coffee Beans ........................................... 33
2.6.4 Roast Coffee Aroma................................................................. 39
2.7 Alkylpyrazines.....