Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This study focused on the potential of comprehensive two-dimensional gas
chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF-MS) for
the improved analysis of volatile wine constituents. Solid phase microextraction
(SPME) in combination with GC×GC-TOF-MS was successfully used for the detailed
investigation of the impact of three commercial Oenococcus oeni lactic acid bacteria
(LAB) strains on the volatile composition of Pinotage wines subjected to malolactic
fermentation (MLF). Due to increased separation power and enhanced sensitivity
obtained by using two orthogonal separations coupled with the structural information
provided by deconvoluted TOF-MS spectra, GC×GC-TOF-MS allowed for the
identification and semi-quantitative analysis of much larger numbers of compounds
compared to previous studies applying one-dimensional gas chromatography. The
combination of univariate and multivariate statistical assessment was used as a
powerful tool for data interpretation. The obtained results contribute significantly to
the understanding of the impact of MLF on the volatile composition of Pinotage wine
Some compounds have been linked to MLF for the first time.
Moreover, the impact of these commercial starter cultures on the composition of
volatile sulfur and nitrogen compounds in the same wines was studied by
one-dimensional gas chromatographic methods with headspace injection and solid
supported liquid-liquid extraction together with sulfur selective detection and tandem
mass spectrometry. This study demonstrated also for the time, the impact of MLF on
the composition of volatile sulfur and nitrogen compounds in Pinotage wine.
GC×GC-TOF-MS was further used for the evaluation of the suitability of a new phase
for stir bar sorptive extraction (SBSE) analysis of wine volatiles. Despite instrumental
complications, beneficial extraction properties of the new stir bar phase for especially
more polar compounds could be demonstrated. In addition, the extraction ability of
this novel phase was evaluated for the analysis of selected thiazoles in wine using
heart-cutting two dimensional gas chromatography in combination with nitrogen
selective detection. Advantageous extraction performance of the new stir bar phase
compared to a conventional polydimethylsiloxane (PDMS) phase for the determined
thiazoles was demonstrated. / AFRIKAANSE OPSOMMING: Hierdie studie het gefokus daarop om die potensiaal van omvattende tweedimensionele
gaschromatografie gekombineer met vlugtyd massaspektrometrie
(GC×GC-TOF-MS) vir die verbeterde analise van vlugtige wynkomponente te
ondersoek. Soliede fase mikro-ekstraksie (SPME) in kombinasie met GC×GC TOF
MS is met sukses aangewend vir ‘n ondersoek na die impak van drie kommersiële
Oenococcus oeni melksuur bakteria (LAB) rasse op die samestelling van die vlugtige
fraksie van Pinotage wyne wat appelmelksuurgisting (AMG) ondergaan het. As
gevolg van die verbeterde skeidingsvermoë en die verhoogte sensitiwiteit wat verkry
word deur twee ortogonale skeidings te kombineer, tesame met die inligting
aangaande die molekulêre struktuur wat die die gedekonvoleerde TOF massaspektra
verskaf, maak GC×GC-TOF-MS die identifikasie en semi-kwantitatiewe analise van
aansienlik meer komponente, in vergelyking met die gebruik van een-dimensionele
gaschromatografie, moontlik.
Die kombinasie van monoveranderlike asook multiveranderlike statistiese evaluering
is gebruik as ‘n kragtige tegniek vir data interpretasie. Die resultate wat verkry is dra
tot ‘n groot mate by tot die ontrafeling en begrip aangaande die impak wat AMG op
die samestelling van vlugtige komponente in Pinotage wyn het. Daar word ook vir die
eerste keer aangetoon dat somminge komponente verband te hou met AMG.
Aanvullend hiertoe is die impak wat hierdie kommersiële kulture (wat gebruik word
om fermentasie te inisieer) op die voorkoms van swawel en stikstof bevattende
vlugtige komponente het bestudeer deur gebruik te maak van een-dimensionele
gaschromatografiese metodes met ‘headspace’ inspuiting en vloeistof-voeistof
ekstraksie tesame met swawel en stikstof selektiewe deteksie en tandem
massaspektrometrie. Hierdie ondersoek werp lig, ook vir die eerste keer, op die
samestelling van vlugtige swawel en stikstof bevattende komponente in Pinotage
wyn.
GC×GC-TOF-MS is ook gebruik vir die evalueering van die toepaslikheid van ‘n
nuwe stasionêre fase vir gebruik met roerstaaf sorptiewe ekstraksie (SBSE) vir die
analisering van vlugtige komponente in wyn. Ten spyte van instrumentele
komplikasies, is die voordele wat hierdie nuwe fase vir die ekstraksie van vernaamlik
meer polêre komponete aangetoon. Vervolgens is die ekstraksievermoë van hierdie
nuwe fase vir die analise van sekere tiasole in wyn met ‘heart-cutting’ twedimensionaly
gaschromatografie in kombinasie met stikstof-selektiewe deteksie gedemonstreer. Verbeterde ekstraksie van die nuwe roerstaaf fase vir die analise
van tiasole, in vergelyking met ‘n tradisionele polydimethylsiloxane (PDMS) fase is
voorts aangetoon.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/18117 |
| Date | 12 1900 |
| Creators | Vestner, Jochen |
| Contributors | De Villiers, A. J., Tredoux, A. G. J., Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 151 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0022 seconds