Thesis (PhD(Agric))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This study focussed on the effect of oxygen on the chemical and sensory evolution of Sauvignon blanc
wine under controlled oxidation conditions. The sensorial interactive effects between Sauvignon blanc
varietal aroma compounds and compounds that typically arise during oxidation of white wines were also
investigated.
In the first research chapter the sensorial interactive effects of Sauvignon blanc impact compounds with
aldehydes typically originating from oxidation of white wines were investigated. Four compounds, 3‐
mercaptohexan‐1‐ol (3MH), 3‐isobutyl‐2‐methoxypyrazine (IBMP), 3‐(methylthio)‐propionaldehyde
(methional) and phenylacetaldehyde were added together in a model wine medium at varying
concentrations. The concentrations chosen were according to those reported in literature to occur in
Sauvignon blanc wines. The sensory effects of these compounds were profiled using a trained sensory
panel. Compounds were first profiled individually and results showed that the change in comcpound
concentration not only led to a change in intensity ratings but also in some cases a change in the
descriptor.
All four compounds in the same sample showed complicated interactive effects. Data were statistically
analysed using relatively novel techniques such as statistical networks that allowed deeper insights into
the interactions involved. Various observations were made such as the contribution of 3MH to the
‘green’ character of the wine, the potent suppressing abilities of methional on 3MH and IBMP and the
additive effect of methional and IBMP contributing to the ‘cooked’ character of the sample. In the second research chapter the effect of repetitive oxidation on a fresh and fruity style Sauvignon
blanc wine was investigated. Results showed the progress and evolution of aromatic and non‐aromatic
compounds during an oxidative aging period. A large range of chemical analyses were conducted
together with extensive sensory profiling. Results showed a decrease in volatile thiols responsible for
the fruity nuances and an increase in oxidation‐related compounds, such as acetaldehyde, during the
course of the oxidation. Sensory profiling showed the evolution of the wine aroma during oxidation. The
wine evolved from a fresh and fruity wine to slight oxidation and then developed extreme oxidative
characteristics. The Control samples (no oxygen added) developed a ‘cooked’ character which could
indicate the formation of reductive compounds in these wines. Conversely, the wines that received a
single dose of oxygen did not develop this flavour and were perceived to be more fresh and fruity than
the Control samples. The evolution of the wine colour was also monitored using a spectrophotometer as
well as a sensory panel and results suggest that the colour of the wine evolved before the disappearance
of the pleasant aroma. The advantages and disadvantages of oxygen exposure to this type of wine style
are discussed as well as the complexity of the wine matrix and sensory interactions occurring in the specific wine. The aim of the third research chapter was again to investigate further sensory interactions between
Sauvignon blanc varietal aroma compounds and an oxidation‐related compound. After the observations
reported in the second research chapter, the inclusion of acetaldehyde in an interaction study seemed
to be of critical importance. Acetaldehyde can reach significant concentrations during oxidation and can
have a detrimental effect on wine aroma. This interaction study included three compounds, 3MH, IBMP
and acetaldehyde. Acetaldehyde was able to effectively mask the ‘green’ character of the sample, while
it also enhanced certain fruity nuances when present at specific concentrations. 3MH was able to
suppress the oxidising character of acetaldehyde when present at sufficient concentrations.
The results from this study clearly showed the complexity of the wine medium and the interactions
involved. It also highlighted the importance of performing these types of sensory studies in a simple
medium opposed to a complex matrix such as wine. The effect of oxygen on various aspects of the wine
was investigated and the combination of chemical and sensory data delivered some interesting
conclusions also involving interactions that occurred. This study paved the way for future investigations
on the sensory relationships of Sauvignon blanc aroma compounds and the role of proper oxygen
management in the production of quality wines. / AFRIKAANSE OPSOMMING: Die doelwit van die studie was om die effek van gekontroleerde oksidasie op die ontwikkeling en
verloop van verskeie chemiese komponente asook die ontwikkeling van die sensoriese profiel van ‘n
Sauvignon blanc wyn te ondersoek. Bykomende studies ondersoek die interaksie/wisselwerking tussen
aromakomponente in ‘n eenvoudige matriks. Interaksies tussen spesifieke Sauvignon blanc kultivargeassosieerde
aromakomponente en komponente wat normaalweg tydens die oksidasie van witwyne
ontwikkel, word ondersoek.
Die eerste navorsingshoofstuk het ten doel om die interaksie tussen tipiese Sauvignon blanc
aromakomponente (of impakkomponente) met aldehiede wat normaalweg tydens oksidasie van
witwyne ontwikkel, na te vors. Vier komponente is in ‘n modelwyn gevoeg teen verskeie konsentrasies,
wat oor die algemeen in die literatuur gerapporteer is om voor the kom in Sauvignon blanc wyne. Die
komponente wat ondersoek is, is: 3‐merkaptoheksanol (3MH), 3‐isobutiel‐2‐metoksiepirasien (IBMP), 3‐
(metieltio)‐propionaldehied (methional) en fenielasetaldehied. Die sensoriese effekte van die
komponente is deur ‘n opgeleide sensoriese paneel geëvalueer. Komponente is eers individueel
geanaliseer en die resultate het getoon dat dat die intensiteit van die spesifieke aroma verander namate
die konsentrasie verander. In sommige gevalle het die beskrywende woord vir die aroma ook verander.
Deur al vier komponente in dieselfde monster te voeg word die ondersoek gekompliseer. Die data is
statisties geanaliseer deur gebruik te maak van relatiewe nuwe tegnieke soos statistiese netwerke wat
dieper insig in die betrokke interaksies bewerkstellig. Verskeie waarnemings word gerapporteer onder
andere die bydrae van 3MH tot die ‘groen’ karakter van die wyn, die kragtige onderdrukkingsvermoë
van methional op 3MH en IBMP asook die opbouende effek van methional en IBMP wat bydra tot die
‘gekookte’ karakter van die monster. Die tweede navorsingshoofstuk is daarop gemik om die effek van herhalende oksidasie op 'n vars en
vrugtige styl Sauvignon blanc wyn te ondersoek en om die vordering en ontwikkeling van aromatiese en
nie‐aromatiese komponente gedurende hierdie tydperk te analiseer. ‘n Wye reeks chemiese
komponente is geanaliseer tesame met omvangryke sensoriese analise. ‘n Afname in die vlugtige tiole,
wat verantwoordelik is vir die vrugtige geure, is gevind tesame met ‘n toename in oksidasie‐verwante
komponente (soos asetaldehied). Sensoriese ondersoeke toon ook die evolusie van die wynaroma
tydens oksidasie. Die wyn het ontwikkel van ‘n vars en vrugtige styl na effense oksidasiegeure waarna
ekstreme oksidasiekarakters waargeneem is. Die Kontrole monsters het ‘n ‘gekookte’ karakter ontwikkel
wat ‘n aanduiding van die ontwikkeling van ‘reduktiewe’ komponente in hierdie wyn kan wees. Aan die
ander kant het wyne wat een suurstofdosering ontvang het, geen van hierdie geure ontwikkel nie en die
wyn is as varser en vrugtiger beskryf in vergelyking met die Kontrole monsters. Die ontwikkeling van die
wynkleur is ook gemonitor deur gebruik te maak van ‘n spektrofotometer asook 'n sensoriese paneel.
Resultate stel voor dat die kleur van die wyn ontwikkel voor die aangename geure begin verdwyn. Die voor‐ en nadele van suurstofblootstelling aan hierdie tipe wynstyl word bespreek asook die
kompleksiteit van die wynmatriks en sensoriese interaksies wat in hierdie spesifieke wyn voorkom.
Die derde navorsingshoofstuk is weereens daarop gemik om die sensoriese interaksie tussen tipiese
Sauvignon blanc kultivar‐geassosieerde aromakomponente en nog ‘n oksidasie‐geassosierde
aromakomponent te ondersoek. Die resultate vanuit die tweede navorsingshoofstuk het die insluiting
van asetaldehied in die interaksiestudie genoodsaak. Asetaldehied kan betekenisvolle konsentrasies
tydens oksidasie behaal en kan ook nadelige effekte op wynaroma hê. Hierdie interaksiestudie het die
volgende drie komponente ingesluit: 3MH, IBMP en asetaldehied. Asetaldehied het die ‘groen’ karakter
van IBMP effektief gemaskeer terwyl dit die waarneming van die vrugtige aroma ondersteun en selfs
verhoog het wanneer dit teen sekere konsentrasies teenwoordig was. 3‐Merkaptoheksanol het die
oksidasiekarakter van asetaldehied onderdruk wanneer dit teen genoegsame konsentrasies
teenwoordig was.
Die kompleksiteit van wyn as ‘n navorsingsmedium is duidelik vanuit die studie veral in die ondersoeking
van interaksie‐effekte tussen komponente. Die belangrikheid van die gebruik van 'n eenvoudige medium
teenoor ‘n komplekse medium vir soortgelyke studies is dus duidelik. Die effek van suurstof op verskeie
aspekte van witwyn is ondersoek en die kombinasie van chemiese en sensoriese data het interessante
gevolgtrekkings gelewer. Die studie het die pad vir toekomstige studies gebaan in terme van sensoriese
interaksies met betrekking tot Sauvignon blanc aroma. Die belangrikheid van oordeelkundige
suurstofbestuur tydens die produksie van kwaliteit wyne is ook uitgelig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86321 |
| Date | 04 1900 |
| Creators | Coetzee, Carien |
| Contributors | Du Toit, Wessel Johannes, Ferreira, Antonio Cesar Silva, 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 | 233 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0025 seconds