Volatile Organic Compounds and Antioxidants in Olive Oil

304 Pages·2007·3.45 MB·English

by  Brett Davis

Volatile Organic Compounds and
Antioxidants in Olive Oil: Their Analysis by
Selected Ion Flow Tube Mass Spectrometry

A thesis submitted in partial fulfilment of the requirements for the degree of

Doctor of Philosophy in Chemistry

at the

University of Canterbury
Christchurch
New Zealand

Brett M. Davis
December 2007

Abstract

The application of Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) to
the analysis of olive oil shows several distinct advantages over more conventional
analysis techniques. The two areas described in this thesis examining olive oil quality
are the analysis of Volatile Organic Compounds (VOCs) and the assessment of
antioxidant activity. VOCs are responsible for the aroma and much of the taste of
olive oil, while antioxidants afford some protection from harmful reactions involving
radical species inside the body by scavenging radicals when olive oil is ingested.
The VOCs of olive oil are used by sensory panel judges to classify oils by
their degree of suitability for human consumption. The major parameters used for this
evaluation are the strengths of any defects and the degree of fruitiness. A defect is an
indication of an undesired process which has occurred in the oil, while fruitiness is a
fragile attribute which denotes a good quality oil and is easily masked by defects.
SIFT-MS was used to measure the strengths of the olive oil defects rancid, winey,
musty, fusty and muddy. Great potential was demonstrated for all defects except
musty and the concentrations of VOCs in olive oil head space were correlated with
the peroxide value, a measure of the degree of oil oxidation. A study aimed at
correlating the strength of the fruitiness attribute as determined by a sensory panel
with the concentrations of VOCs in olive oil head space was unsuccessful.
The SIFT-MS Total Oxyradical Scavenging Capacity (TOSC) assay was used
to measure olive oil antioxidants. This assay measures all antioxidants in oil, not only
those removed by extraction with a solvent, as it is conducted in an emulsion.
SIFT-MS-TOSC assay results were found to correlate well with those of the widely
used Folin-Ciocalteu assay and the total concentration of phenolic compounds present
in olive oil. Discrepancies between the two assays were most likely due to
ABSTRACT
hydrophobic antioxidants which are measured by the SIFT-MS-TOSC assay but not
the other tests.
Acknowledgements
Over the course of this research I have interacted with many people, not all of
whom I will remember to name here. My sincere thanks to all of these people, you
made many occasions over the past few years pleasant when they could easily have
been otherwise.
I would like to thank my supervisors, Murray McEwan and Senti Senthilmohan
for guidance and valuable advice. Thanks are due to everyone at Syft Technologies,
past and present, especially the Science team of those previously named and
additionally Greg Francis, Vaughan Langford, Daniel Milligan, Barry Prince and Paul
Wilson. Without the equipment, work atmosphere and supplemental employment
available at Syft Technologies this research would not have been possible. Thank you to
Olives New Zealand, especially Don Beaven, Alastair Bridge, Don Cross, Margaret
Edwards and Ian Manson, without whom I would have had no olive oil to analyse. I
would also like to thank Helen Clausen, Judy Wilson and Patrik and Eleanor Hulsman
for inspiration, advice and enthusiasm. Thank you to all the olive growers and
processors who donated olive oil for this project.
This research was funded by a Technology for Industry Fellowship from the
New Zealand Foundation for Research Science and Technology. This support was
essential and is very much appreciated.
Forewarned is forearmed, and I am grateful to Ben Perston (the Matlab guru)
and Michelle Hamilton for forearming me in the later stages of this research. Both also
assisted me when wading through the literature of multivariate statistical methods. My
sanity and study have also benefited from the presence of David Bones, James Bull and
ACKNOWLEDGEMENTS
Sam Edwards. I must also thank the marine group, especially Sonja, Jenny and Annabel
for saving me from the HPLC gremlins. Thanks to Wayne MacKay and Nick Oliver in
the mechanical workshop for their expertise and tact in dealing with an array of original
problems.
Thank you to my family, especially my mother, who (mostly) restrained her
constant urge to ask when I was going to finish. Lastly, a big thank you to Kelly for her
remarkable tolerance.
List of Publications
At the time of printing, the following peer-reviewed publications have resulted
from this research:

Brett M. Davis, Senti T. Senthilmohan, Paul F. Wilson and Murray J. McEwan,
Major volatile compounds in head-space above olive oil analysed by selected ion
flow tube mass spectrometry, Rapid Commun. Mass Spectrom., 2005, 19: 2272-
2278.

Brett M. Davis and Murray J. McEwan, Determination of Olive Oil Oxidative
Status by Selected Ion Flow Tube Mass Spectrometry, J. Agric. Food Chem.,
2007, 55: 3334-3338.
LIST OF PUBLICATIONS
Contents
List of Abbreviations...................................................................................................1
Introduction..................................................................................................................3
1. Olive Oil Introduction.............................................................................................7
1.1 Olive Oil Production......................................................................................8
1.2 Olive Oil Components.................................................................................12
1.3 Olive Oil Testing..........................................................................................17
1.4 References………………………………………………………………....22
2. The Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) Technique........25
2.1 Instrumentation............................................................................................25
2.2 Interpreting the Results................................................................................32
2.3 References………………………………………….………………………40
3. Olive Oil Volatile Organic Compounds...............................................................41
3.1 VOC Analysis Techniques...........................................................................41
3.2 Identified VOCs...........................................................................................43
3.3 Olive Oil Oxidation......................................................................................46
3.4 Olive Oil Defects.........................................................................................49
3.5 References……………………....………………………………………….53
4. VOC Analysis Method...........................................................................................55
4.1 Introduction..................................................................................................55
4.2 Initial Investigation......................................................................................55
4.3 Assignment of Product Masses....................................................................59
4.4 Concluding Remarks....................................................................................82
4.5 References………………………...………………………………………..83
5. Olive Oil Defects.....................................................................................................85
5.1 Introduction..................................................................................................85
5.2 Rancid Olive Oil..........................................................................................85
5.3 Winey Olive Oil.........................................................................................104
5.4 Musty Olive Oil.........................................................................................111
5.5 Fusty Olive Oil...........................................................................................114
5.6 Muddy Olive Oil........................................................................................117
5.7 References……………………………..………………………………….123
6. Olive Oil Sensory Attributes...............................................................................125
6.1 Introduction................................................................................................125
6.2 Method.......................................................................................................125
6.3 Results........................................................................................................127
6.4 Summary....................................................................................................154
6.5 References……………….………………………………………………..155
7. Antioxidant Introduction....................................................................................157
7.1 Introduction................................................................................................157
7.2 Biologically Important Radical Species.....................................................157
7.3 Radical Scavengers in Lipids.....................................................................160
7.4 Antioxidant Assays....................................................................................161
7.5 References…………….…………………………………………………..172
8. TOSC Assay Development..................................................................................175
8.1 SIFT-MS-TOSC Assay Method................................................................175
8.2 SIFT-MS-TOSC Assay Development.......................................................181
8.3 References…………….…………………………………………………..191
CONTENTS
9. SIFT-MS-TOSC Assay Characterisation..........................................................193
9.1 Introduction................................................................................................193
9.2 Method.......................................................................................................193
9.3 Results........................................................................................................200
9.4 Summary....................................................................................................218
9.5 References……...…………………………………………………………220
10. General Conclusions..........................................................................................221
10.1 Relationships Between Sensory Attributes and SIFT-MS Analysis..........221
10.2 The SIFT-MS-TOSC Assay for Antioxidant Analysis..............................224
10.3 References…………..…………………………………………………….228
Appendices
A. Multivariate Statistical Techniques...................................................................229
A.1 Introduction................................................................................................229
A.2 Principal Component Analysis (PCA).......................................................234
A.3 Partial Least-Squares Regression...............................................................251
A.4 References………………………..……………………………………….275
B. Statistics................................................................................................................277
B.1 Standard Deviation.....................................................................................277
B.2 Robust Standard Deviation........................................................................278
B.3 Standard Error of Slope.............................................................................278
B.4 Coefficient of Determination.....................................................................279
B.5 References……………………………….……………………………….280
C. Matlab Programs and Sensory Assessment Sheets..........................................281
C.1 Introduction................................................................................................281
C.2 Matlab Programs........................................................................................281
C.3 Olive Oil Sensory Assessment Sheets.......................................................289
C.4 References......................................……………………………………….293