Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The present study deals in the first instance with the improvement of current analytical
techniques for the analysis of the non-volatile content of wines. An improved sample
preparation method, using solid phase extraction (SPE), was initially developed for the
analysis of organic acids, sugars and phenolic compounds. Consequently, modem
analytical methodologies were assessed to obtain optimal techniques for the separation of
various non-volatile compounds. A capillary electrophoresis (CE) method, demonstrably
more reliable than currently used high performance liquid chromatography (HPLC) and CE
methods, is proposed for the analysis of organic acids. HPLC with refractive index (RI) or
evaporative light scattering detection (ELSD) proved more suitable than CE for the analysis
of sugars in dry wines. Liquid-chromatography-mass spectroscopy (LC-MS) offered
superior sensitivity and resolution compared to the relatively new technique of CE-MS for
the analysis of wine phenolics. LC-MS was further applied for the efficient and sensitive
analysis of non-coloured phenolics and anthocyanins in wine. Negative- and positive
electrospray ionisation, respectively, were used in conjunction with an ion-trap mass
analyzer, for the identification of 34 phenolics and 31 anthocyanins in red wine samples.
Complementary CE and LC methods were developed to allow the identification of artificial
dyes in red wines, added illegally to improve their colour. Also, the application of stir bar
sorptive extraction (SBSE) with liquid desorption and micellar electrokinetic
chromatography (MEKC) for the analysis of bitter acids in beer is reported.
In the second part of the thesis, the analytical results obtained for South African red and
white wines were evaluated. Following comparison of the results with literature reports,
several pattern recognition techniques were employed. A classification function obtained by
linear discriminant analysis (LDA) was used to classify both red and white wines according
to variety, based on their chemical composition. This classification is achieved independent
of the factors of wine age or geographical origin, making it useful for authenticity
evaluation. / AFRIKAANSE OPSOMMING: Hierdie studie het as primêre doel die verbetering van bestaande analitiese metodes vir die
analise van nie-vlugtige komponente in wyn. In die lig hiervan, is eerstens 'n toepaslike
monster-voorbereidingstegniek, gebasseer op soliede fase ekstraksie (SPE), ontwikkel vir
die gelyktydige analise van organise sure, suikers en fenoliese komponente vanuit die wyn
matriks. Vervolgens is moderne analitiese rtietodes ondersoek en gepastde
skeidingstegnieke is ontwikkel vir die verskillende chemiese wyn-komponente. Kappillêre
elektroforese (CE) en hoë-druk vloeistof-chromatografie (HPLC) in kombinasie met
verskeie deteksie-metodes is vergelyk. Hieruit is 'n verbeterde CE metode vir die analise
van organise sure is ontwikkel, terwyl HPLC in kombinasie met refraksie-indeks- en
verdampings lig verstrooiings deteksie (ELSD) die beste resultate lewer vir die analise van
suikers in droë wyne. Die toepasbaarheid van vloeistof-chromatografie met massa
spektrometriese deteksie (LC-MS) vir die analise van fenoliese komponente is
gedemonstreer, terwyl CE-MS onvoldoende resolusie en sensitiwiteit toon vir die analises.
LC-MS is vervolgens ook gebruik vir die identifikasie van 34 fenoliese verbindings en 31
antosianiede in rooi wyn. Komplementêre HPLC en CE metodes is ontwikkel vir die
identifikasie van onwettige sintetiese kleurstowwe in' rooi wyn. 'n Addisionele monstervoorbereidingsstap,
roerstaaf sorptiewe ekstraksie (SBSE), is saam met vloeistof-desorpsie
en misellêre elektrokinetiese chromatografie (MEKC) gebruik vir die analise van hops
bitter sure in bier.
In die tweede deel van die tesis word die resultate verkry m.b.v. bg. tegnieke vir die analise
van Suid-Afrikaanse rooi- en wit wyne, bespreek. Die resultate is vergelyk met waardes uit
die literatuur, en verskeie statistiese metodes is gebruik om die data te ondersoek. Met
behulp van chemometriese metodes is 'n klassifikasie funksie verkry wat die klassifikasie
van Suid-Afrikaanse wyne volgens druifsoort, gebasseer op die chemiese samestelling van
die wyne, toelaat. Die klassifikasie is moontlik, onafhanklik van die ouderdom of
geografiese oorsprong van die wyne.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49850 |
| Date | 12 1900 |
| Creators | De Villiers, A. J. (Andre Joubert) |
| Contributors | Sandra, P. J. F., Crouch, A. M., Stellenbosch University. Faculty of Science . Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 282 p. : ill. |
| Rights | Stellenbosch University |
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