Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In recent years South African wines have been under the spotlight due to references in the
international wine media to a distinctive ‘burnt rubber’ character. Many winemakers and wine
experts argued that the peculiar character could be ascribed to winemaking errors linked to
mismanaged fermentation. An alternative possible source of the taint was identified in the coal tar
creosote used as a wood preservative in vineyard trellis systems. South African regulations allow
for the use of creosoted utility poles in agricultural land, but in Europe and USA their usage has
been highly regulated and even banned for certain applications. Contamination of foodstuff by
polycyclic aromatic hydrocarbons (PAHs) is one of the major motives for the banning of creosote in
Europe and USA. Some of the compounds in the creosote mixture display very strong odour
characteristics and for this reason it became the focus of attention for the present study.
The overall aim of this study was to determine if vines trellised with creosoted posts could
accumulate or absorb the various malodorous compounds deriving from the wood treatment onto
the grape berries. These compounds could then be extracted from the grape berries into the wine
during alcoholic fermentation, creating quality and sensory problems. Chapter 2 of this thesis gives
an overview of the extensive literature that deals with methods of analysis of PAHs and
malodorous phenols using both Gas Chromatography (GC), as well as High Performance Liquid
Chromatography (HPLC). New methods for sample preparation, as well as analysis of PAHs using
HPLC-Diode Array Detector (DAD), were developed and the results reported in Chapter 3. It was
demonstrated that Sauvignon blanc experimental wines contained only chrysene at very low levels.
The concentrations of chrysene found in the experimental wines are within the prescribed
parameters as established by The Commission of the European Communities. Since no other PAH
compounds were found in the samples analysed, it was concluded that the experimental wines
were safe for human consumption and complied with EU regulations. The effect of vineyard posts
on the sensorial characteristics of wine is discussed in Chapter 4. Creosoted poles were found to
be responsible for an off-flavour described as ‘burnt rubber’ and ‘tarry’ in Merlot wines produced
from grapes grown in close proximity to the posts. Following some of the reported findings, new guidelines have been introduced in the
Integrated Production of Wine certification, which advise against the use of creosoted poles for
vineyard trellising. This preliminary but important guideline will bring the South African wine
industry a step closer to the fulfilling the obligations for food safety as required by the legislation of
our major export partners. Future investigations are recommended to completely understand and
evaluate the cumulative effect of creosoted posts in a fully trellised vineyard. / AFRIKAANSE OPSOMMING: Oor die afgelope paar jaar is Suid-Afrikaanse wyne onder die soeklig geplaas as gevolg van
verwysings in die internasionale wynmedia na ‘n duidelike ‘gebrande rubber’-karakter. Baie
wynmakers en wyndeskundiges het aangedui dat hierdie besonderse karakter toegeskryf kan word
aan wynbereidingsfoute wat verband hou met gisting wat wanbestuur is. ‘n Alternatiewe moontlike
oorsprong van die smaak is geïdentifiseer in die koolteer wat as ‘n houtpreserveermiddel in
wingerdopleistelsels gebruik word. Suid-Afrikaanse regulasies maak voorsiening vir die gebruik
van kreosoteerde nutspale in landbougrond, hoewel hulle gebruik in Europa en die VSA hoogs
gereguleerd en in sommige gevalle selfs verbied is. Die besmetting van kossoorte deur polisikliese
aromatiese koolwaterstowwe (polycyclic aromatic hydrocarbons (PAHs)) is een van die
vernaamste redes vir die verbanning van kreosoot in Europa en die VSA. Sommige van die
verbindings in die kreosootmengsel het baie sterk geurkenmerke en daarom is dit die fokus van die
huidige studie.
Die oorhoofse doelwit van hierdie studie was om te bepaal of wingerde wat op kreosoteerde
pale opgelei is, die verskillende onwelriekende verbindings afkomstig van die houtbehandeling in
die druiwekorrels kan akkumuleer of absorbeer. Hierdie verbindings sou dan tydens alkoholiese
gisting uit die druiwekorrels in die wyn geëkstraheer kon word, wat aanleiding sou gee tot
kwaliteits- en sensoriese probleme. Hoofstuk 2 van hierdie tesis verskaf ‘n oorsig van die
breedvoerige literatuur wat handel oor metodes om PAH’s en onwelriekende fenole met behulp
van beide gaschromatografie (GC) en hoëdrukvloeistofchromatografie (HPLC) te analiseer. Nuwe
metodes is ontwikkel om monsters voor te berei en om PAH’s met behulp van ‘n HPLC-diode array
detector (DAD) te analiseer. Die resultate word in Hoofstuk 3 gerapporteer. Daar is aangetoon dat
die eksperimentele Sauvignon blanc-wyne chriseen teen baie lae vlakke bevat het. Die
konsentrasies van chriseen wat in die eksperimentele wyne gevind is, is binne die voorgeskrewe
parameters van die Kommissie van die Europese Gemeenskap. Aangesien daar nie ander PAHverbindings
in die geanaliseerde monsters gevind kon word nie, is daar tot die gevolgtrekking
gekom dat die eksperimentele wyne veilig is vir menslike verbruik en aan die EG-regulasies voldoen. Die effek van wingerdpale op die sensoriese kenmerke van wyn word in Hoofstuk 4
bespreek. Kreosoteerde pale is gevind wat verantwoordelik is vir ‘n wangeur in Merlot-wyne
afkomstig van druiwe wat naby die pale gegroei het en wat as ‘gebrande rubber’ en ‘teeragtig’
beskryf is.
Op grond van sommige van die gerapporteerde bevindings, is nuwe riglyne ingesluit in die
sertifisering vir die Geïntegreerde Produksie van Wyn, wat aanbeveel dat kreosoteerde pale nie vir
wingerdoplei gebruik word nie. Hierdie voorlopige, maar belangrike riglyn sal die Suid-Afrikaanse
wynbedryf al beter in staat stel om te voldoen aan die voedselveiligheid regulasies wat vereis word
deur die wetgewing van ons belangrikste uitvoervennote. Toekomstige ondersoeke moet aangewend word om die kumulatiewe effek van kreosoteerde pale in volledig opgeleide wingerde
ten volle te verstaan en te evalueer. / Indaba Scholarship and Winetech for their financial support
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80197 |
| Date | 03 1900 |
| Creators | Panzeri, Valeria |
| Contributors | McKay, Marianne, Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 83 p. : col. ill. |
| Rights | Stellenbosch University |
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