Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The varietal character of Sauvignon blanc wine is mostly defined by the balance between tropical and green vegetative flavour nuances. Grape derived methoxypyrazines are the main aroma contributors towards green vegetative flavours. Methoxypyrazines are heat and light sensitive. Due to warm climatic conditions in South Africa, methoxypyrazine levels decrease during grape ripening. The addition of food flavourings to Sauvignon blanc wine, a practice known as spiking, has occurred in the past to improve the green character of the wines. Adding flavourings to wine and selling the wine as natural certified wine is illegal in South Africa. Currently, adulterated Sauvignon blanc wines are identified using gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) methods to quantify methoxypyrazines and compare levels to an established database. Although of high sensitivity, GC-MS and LCMS methods are costly and time consuming, therefore not optimal for routine screening of wines. Hence the need for the development of a fast and cost effective method for routine screening of large amounts of wines to identify adulteration. Small scale vinification practices were used to prepare experimental Sauvignon blanc wine. Flavourings were added to Sauvignon blanc grape juice before fermentation, during the preparation of experimental spiked wines. Control wines, containing no flavouring, were also prepared. Commercial wines were spiked after fermentation and bottling. Each wine was only spiked with a single flavouring. The flavourings added were the juice of homogenised fresh green peppers and commercially available flavourings for wine. The following commercial flavourings were used: green pepper, asparagus, grassy and tropical. The above mentioned wines were analyzed using Fourier transform infrared (FT-IR) spectroscopy, GC-MS, LC-MS and descriptive sensory analysis. The FT-IR techniques used were Fourier transform mid infrared (FT-MIR) transmission, FT-MIR attenuated reflection and Fourier transform near infrared (FT-NIR) reflection spectroscopy. The data was interpreted using the following multivariate statistical techniques: principal component analysis (PCA), partial least squares discrimination (PLS-D) and conformity testing. Multivariate models constructed from FT-MIR and FT-NIR data were able to discriminate between spiked and control wines. Sensory analysis results clearly showed differences between non-spiked wines and spiked wines with 3-isobutyl-2-methoxypyrazine concentrations 10 times higher than naturally occurring in wine. Differences between control and spiked wines with concentrations of 3-isobutyl-2-methoxypyrazine similar to concentrations naturally occurring in wines could not be detected to prove adulteration conducting sensory analysis. However, differences between control and spiked wines with levels of 3-isobutyl-2-methoxypyrazine similar to levels naturally occurring in wines could be detected using FT-IR data in conjunction with multivariate statistics. This study showed that, FT-IR spectroscopy in conjunction with multivariate statistical methods can be a possibility for the screening and identification of wines suspected of adulteration in terms of added flavourings. Descriptive sensory analysis also proved to be a potentially useful tool. However screening and training of potential panel members are time consuming. / AFRIKAANSE OPSOMMING: Die variëteitskarakter van Sauvignon blanc wyn word grotendeels gedefinieer deur die balans tussen tropiese en groen vegetatiewe aromas. Metoksipirasiene is die hoof aroma verbindings wat verantwoordelik is vir groen vegetatiewe aromas. Metoksipirasien is hitte- en ligsensitief. Warm klimaatsomstandighede in Suid-Afrika het tot gevolg dat metoksipirasien konsentrasies daal tydens druif rypwording. Sauvignon blanc wyne is in die verlede vervals deur middel van die byvoeging van vars groen soetrissies om die groen vegetatiewe karaktereienskappe van die wyne te bevorder. Die byvoeging van geurmiddels of plantekstrakte by wyn en verkoop van daardie wyn as gesertifiseerde natuurlike wyn is onwettig in Suid-Afrika. Tans word vervalsde wyne met behulp van gaschromatografie-massaspektrometrie (GC-MS) en vloeistofchromatografie-massaspektrometrie (LC-MS) opgespoor. Kwantifisering van metoksiepirasien konsentrasies in wyne en druiwesappe word vergelyk met konsentrasies in ‘n bestaande databasis. Alhoewel GC-MS en LC-MS hoë sensitiwiteitsmetodes is, is dit duur en tydrowende metodes, dus nie optimaal vir roetine sifting nie. Dus word ‘n koste- en tydseffektiewe roetine metode benodig om vervalsing van wyne op te spoor. Eksperimentele wyne is op klein skaal berei. Geurmiddels is voor fermentasie by die druiwesap gevoeg. Kontrole wyne waarby geen geurmiddels gevoeg is nie, is ook berei. Kommersiële wyne is gegeur na fermentasie en bottelering. Elke wyn is met ‘n enkele geurmiddel gegeur. Gehomogeniseerde vars groen soetrissie asook kommersieel beskikbare geursels vir wyn is gebruik. Die volgende kommersiële geursels is gebruik: groen soetrissie, aspersie, gras en tropiese geursel. Die volgende analitiese tegnieke is gebruik vir analisering van bogenoemde wyne: Fourier transformasie infrarooi (FT-IR) spektroskopie, GC-MS, LC-MS en beskrywende sensoriese analise. Die spesifieke FT-IR tegnieke wat gebruik is, is: Fourier transformasie mid-infrarooi (FT-MIR) transmissie, FT-MIR verswakte weerskaatsing en Fourier transformasie naby-infrarooi (FT-NIR) reflektansie. Die volgende multiveranderlike statistiese tegnieke is gebruik ter interpretasie van data: hoof komponent analise (PCA), parsiële kleinste kwadraat diskriminant analise (PLS-D) en gelykvormigheidstoetsing. Multiveranderlike modelle, bereken met behulp van FT-MIR en FT-NIR data, kon diskrimineer tussen gegeurde en kontrole wyne. Resultate wat verkry is tydens sensoriese analises het duidelike verskille uitgewys tussen gegeurde en kontrole wyne met betrekking tot 3-isobutiel-2- metoksipirasien konsetrasies waar 3-isobutiel-2-metoksipirasien konsentrasies 10 keer hoër was as wat natuurlik voorkom in wyn. Geen beduidende verskille kon waargeneem word in gevalle waar wyne vervals is met laer konsentrasies van geurmiddels deur sensoriese data te ontleed nie. Nietemin, statisitiese verskille tussen kontrole en vervalsde wyne kon waargeneem word vir lae-konsentrasie-geurmiddel vervalsde wyne deur FT-IR data met behulp van multiveranderlike statisitiese metodes te ontleed. Hierdie studie het gewys dat FT-IR in kombinasie met multiveranderlike statistiese tegnieke spesifiek hoof komponent analise (PCA) en parsiële kleinste kwadraat diskriminant analise (PLS-D) asook gelykvormigheidstoetsing bruikbare tegnieke is om te onderskei tussen kontrole (egte natuurlike) en vervalsde wyne ten opsigte van die byvoeging van geurmiddels. Beskrywende sensoriese analise kan ook nuttig gebruik word, alhoewel keuring en opleiding van paneellede tydrowend is.

Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Hen egg white lysozyme (HEWL; muramidase; EC 3:2:1:17) is an enzyme present in high concentrations in chicken (Gallus gallus) egg whites. It hydrolyses the link between N-acetylmuramic acid and N-acetylglucosamine in Gram positive bacterial cell walls, resulting in cell death. It is thus active against lactic acid bacteria (LAB), which may be present in grape juices and musts. These bacteria are responsible for malolactic fermentation of wines although many species, particularly of the genera Lactobacillus and Pediococcus, are considered spoilage organisms. The growth of LAB is therefore closely monitored and controlled during winemaking. The most common means of control is growth inhibition by chemical treatment (usually with SO2). Lysozyme is a commonly used wine processing aid, complementing the antimicrobial activity of SO2 . It allows for lower doses of SO2 to be used, thus improving the wholesomeness of wine. The OIV (Organisation Internationale de la Vigne et du Vin) approved its use in quantities up to 500 mg per liter of wine in 1997. This study evaluated the effect of different secretion signals on the secretion of lysozyme by the haploid auxotroph Saccharomyces cerevisiae strain FY23. Secretion by an industrial strain (VIN13) transformed with a single copy of the HEWL gene with the MF-a secretion signal under the control of the PGK1 (phosphoglycerate kinase 1) prompter and terminator was also evaluated. In the case of FY23 four secretion signals were used, namely the native lysozyme signal and the S. cerevisiae mating factor-a signal as well as mutants of these signals. These mutants incorporated two additional arginines at the N-terminus of the signals immediately downstream of the terminal methionine. The effect of these mutations was to increase the positive charge of the secretion signal N-terminals. The secretion signal-lysozyme fusions were placed under the regulation of the S. cerevisae PGK1 gene’s promoter and terminator. The resulting expression cassettes were cloned into integrating vectors YIpLac211 and pDMPOF1b and episomal vector pHVX2. These were used to transform FY23 and VIN13. FY23 as well as VIN13 transformants were evaluated in an artificial medium designed to reflect the nutrient content of grape juice, with particular attention being paid to assiminable nitrogen. Three hexose concentrations were tested in order to determine the effect thereof on lysozyme secretion titer. Lysozyme secreted under all tested growth conditions was found to be too low for detection by either enzymatic assay or HPLC-FLD. For this reason secreted lysozyme was isolated and concentrated 10x by means of cation-exchange. Subsequently, lysozyme concentrations in the concentrates was determined by means of the aforementioned techniques. SDS-PAGE analysis of lysozyme concentrates was also performed. No significant differences were found between native or MF-a secretion signals and their mutated counterparts in terms of secretion titer or proteolytic maturation. Lysozyme secreted with the MF-a signal was found to be misprocessed in all cases, with both an authentically processed and a larger form, in which the secretion signal was not completely removed, being present. Lysozyme secreted with the native signal appeared to be correctly processed in all cases. Secretion titer from high copy number episomal FY23 tranformants was similar to that of integrants containing a single copy of the gene. Sugar concentration affected lysozyme production, with higher quantities of the enzyme being secreted when higher initial sugar concentrations were used. Lysozyme titers were extremely low (< 0:25 mg/L) with all expression cassettes under all the tested conditions with both FY23 and VIN13. In the case of the VIN13’s a lower final biomass was found for the secretor strain tested in comparrison to the VIN13 wild-type. / AFRIKAANSE OPSOMMING: Hoendereierwitlisosiem (HEWL; muramidase, EG 3:2:1:17) is ´n ensiem teenwoordig in hoë konsentrasies in hoender (Gallus gallus) eierwitte. Dit hidroliseer die binding tussen N-asetielmuramiensuur en N-asetielglukosamien in Gram positiewe bakteriese selwande, wat tot seldood lei. Dit is dus aktief teen melksuurbakterieë (MSB), wat in druiwesap en mos teenwoordig kan wees. Hierdie bakterieë is verantwoordelik vir appelmelksuurgisting van wyne, hoewel baie spesies, veral van die genera Lactobacillus en Pediococcus, ook as bederforganismes beskou word. Die groei van MSB word dus noukeurig tydens wynbereiding gemoniteer en beheer. Die algemeenste wyse van beheer is groei-inhibisie deur chemiese behandeling (gewoonlik SO2). Lisosiem is ´n algemeen gebruikte wyntoevoegingsmiddel en vul die antimikrobiese aktiwiteit van SO2 aan. Met lisosiem kan ´n laer dosis van SO2 gebruik word, wat lei tot ´n verbetering van die heilsaamheid van die wyn. Die OIV (Organisasie Internationale de la Vigne et du Vin) het die gebruik daarvan goedgekeur tot en met 500 mg per liter wyn vanaf 1997. Hierdie studie het die effek van verskillende sekresieseine op die uitskeiding van lisosiem deur die haploïede ouksotrofe Saccharomyces cerevisiae stam, FY23, geëvalueer. Uitskeiding deur ´n industriële stam (VIN13), wat getransformeer is met ´n enkelkopie van die HEWL-gene met die MF-a sekresiesein onder die beheer van die PGK1 (Fosfogliseraat kinase 1) promotor en termineerder, is ook geëvalueer. In die geval van FY23 is vier sekresieseine gebruik, naamlik die inheemse lisosiemsein, S. cerevisiae MF- a sein, asook mutante van hierdie seine. Hierdie mutante het twee bykomende arginienresidu’s by die N-terminus van die seine direk stroom-af van die terminale metionien. Die effek van hierdie mutasies was om die positiewe lading van die uitskeidingsein N-terminale te verhoog. Die gevolglike uitdrukkingskassette is in die integrasievektor YIpLac211 en pDMPOF1b, en die episomale vektor pHVX2, gekloneer. Dit is gebruik om VIN13 en FY23 te transformeer. FY23, sowel as VIN13-transformante, is geëvalueer in ´n kunsmatige medium wat ontwerp is om die voedingsinhoud van druiwesap te weerspieël, met besondere aandag aan assimileerbare stikstof. Drie heksose konsentrasies is getoets om te bepaal wat die uitwerking daarvan op die lisosiemsekresietiter is. Onder alle groeitoestande was die isosiem wat uitgeskei is, te laag om deur ensimatiese toetse of HPLC-FLD bepaal te word. Om hierdie rede is uitgeskeide lisosiem geïsoleer en 10x gekonsentreer deur middel van katioon-uitruiling. Daarna is lisosiemkonsentrasies bepaal deur middel van bogenoemde tegnieke. SDS-PAGE-ontleding van lisosiemkonsentraat is ook uitgevoer. In terme van sekresietiter of proteolitiese maturasie, is geen beduidende verskille gevind tussen inheemse of MF-a sekresieseine en hul gemuteerde eweknieë nie. Lisosiem wat deur die MF-a sein uitgeskei is, is in alle gevalle foutief geprosesseer, met ´n teenwoordigheid van beide die regte produk en ´n groter produk, waarin die uitskeidingsein nie heeltemal verwyder word nie. Lisosiem wat met die inheemse sein uitgeskei is, blyk in alle gevalle korrek verwerk te wees. Sekresietiter van ´n aantal hoë-kopie episomale FY23-transformante was soortgelyk aan dié van integrante met ´n enkelkopie van die geen. Suikerkonsentrasie beïnvloed lisosiemproduksie, met ´n hoër hoeveelheid van die ensiem wat uitgeskei word wanneer die aanvanklike suiker in hoër konsentrasies gebruik is. Lisosiemtiters was baie laag (< 0:25 mg/L), met al die kassette onder al die getoetste toestande vir beide FY23 en VIN13. In die geval van die VIN13’s, is ´n laer finale biomassa vir die uitskeidingstam in vergelyking met die VIN13 wilde-tipe gevind.

Thesis (MSc)--Stellenbosch University, 1964. / ENGLISH ABSTRACT: The influence of manganese sulphate sprays on the yield and ripening of fruit of manganese-deficient Vitis vinifera L. (cv. Pinotage) plants was investigated. Ripening was determined in terms of changes in concentration of the indivi= dual and total sugars and organic acids. Increasing concentrations of manganese sulphate resulted in significant increases in the manganese content of the leaves. The higher levels of manganese were associated with an increase in yield. Ripening, however, was retarded, in that the percentage sugar of the fruit was decreased and titrable acid content increased. The principal sugars present in the fruit were sucrose, glucose, fructose and xylose. Malic and tartaric acids were the main organic acid constituents. Glucose and fructose increased sharply, and sucrose and xylose slightly during ripening of the fruit, whereas malic and tartaric acid de= creased. Glucose, fructose, tartaric and malic acid tended to increase with increasing manganese content. Sucrose and xylose were not appreciably affected. An application of 1% manganese sulphate can be recommend- · ed for manganese deficient vineyards, as it results in an increased yield, in addition to delaying ripening until a more favourable time for handling. Furthermore, the lowered sugar content of the fruit may be advantageous for the pro= duction of dry wines from Pinotage grapes . / AFRIKAANSE OPSOMMING: Die invloed van mangaansulfaatbespuiting op die opbrengs en vrugrypwording van Vitis vinifera L. cv. Pinotage, wat aan ernstige mangaantekorte gely het, is ondersoek. Rypwording is met betrekking tot veranderings in die konsentrasies van totale en indiwiduele suikers en sure bepaal. 2. Toenemende konsentrasies Mnso4 (van O.2% tot l.O%) het n betekenisvolle toename in die mangaangehalte van die blare (van 3 tot 80 d.p.m.) tot gevolg gehad. Die ver= hoogde mangaangehalte het gepaard gegaan met n toe= name in opbrengs, terwyl rypwording vertraag is, deurdat die suikerpersentasie en die titreerbare suurgehalte ver= meerder is in vergelyking met die kontroleplante. 3. Die vernaamste suikers in die vrugte was sukrose, glukose, fruktose en xilose. Glukose en fruktose het vinnig en sukrose en xilose geleidelik toegeneem met die verloop van rypwording. In die ryp vrugte was glukose en fruk= tose oorheersend. Glukose en fruktose was geneig om toe te neem met toenemende mangaangehalte, terwyl sukrose en xilose nie beinvloed is nie. 4. Appelsuur en Wynsteensuur was die oorwegende sure in die vrugte. Beide hierdie sure het gedurende rypwording verminder. Hulle konsentrasies het oor die algemeen toegeneem namate die mangaankonsentrasie verhoog is. 5. Dit is afgelei dat bespuiting met 1.0% MnS04 aanbeveel kan word vir wingerde met mangaantekorte, daar dit n toename in opbrengs, gepaard met 'n vertraging in rypwording tot gevolg gehad het. So 'n vertraging mag moontlik in parstyd voordelig wees. Die verlaagde suikerpersentasie van die vrugte is moontlik gunstig vir die bereiding van droe wyne, waarvoor Pinotage hoofsaaklik gebruik word.

Thesis (MScAgric)--Stellenbosch University, 1974. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Phenolic compounds are important quality indicators of a red wine, as they can contribute to the colour of a young red wine, colour stability during ageing as well as astringency, bitterness, body and overall mouthfeel properties. Wine composition is commonly influenced by winemaking and viticultural practices. In South Africa it often happens that vines are excessively vigorous, resulting in canopies that are too dense, which in turn could have a negative effect on the quantity and quality of the grapes produced. Viticultural practices such as judicious canopy management and irrigation are designed to control vine vigour and yield, thus improving fruit ripening and colour development. Artificial shading and water deficit have been reported to have an influence on the sensory properties of red wine as well as on the flavonoid composition. These effects are dependent on a number of factors, however, including the season, cultivar, light intensity, and the extent and timing of water deficit. There is limited research on the possible interactive effects of grapevine water deficits and canopy manipulation on grape and wine flavonoid composition in Shiraz, as well as the relationships between berry and wine composition. We thus investigated the effect of canopy reduction in combination with water deficit on the phenolic and colour composition of Shiraz grapes at different levels of ripeness, and in their corresponding wines after alcoholic and malolactic fermentation as well as after six months’ ageing. This study found that it is possible to improve the phenolic composition of grapes and wine by shoot removal, and some of the tendencies in the wines were also observed after the ageing period. If the shoot removal is not performed at a very early stage, sunburn damage can occur and this will result in berries with a lower mass and volume at harvest due to excessive exposure without the berry having adapted to the imposed conditions. Harvesting at different ripeness levels also affected the chemical and phenolic composition of the grapes and resulting wines. The water deficit effect on most phenolic parameters measured in the grapes and wine was not as prominent as that of the canopy manipulation treatment. This study improved our understanding of how an improvement in the canopy microclimate of Shiraz could be reflected in the phenolic composition of wines, along with a potentially important effect of harvesting date. On this basis it may be possible to attain a specific wine style. Harvesting at a ripe stage, for example, could result in the production of wines with higher colour density and astringency, while unripe grapes could result in wines with higher levels of perceivable fresh berry attributes. In particular, canopy reduction could increase the astringency and body of wines made from grapes subjected to water deficit. / AFRIKAANSE OPSOMMING: Fenoliese verbindings is belangrike kwaliteitsparameters van rooiwyn, aangesien dit kan bydra tot die kleur van ‘n rooiwyn, kleurstabiliteit tydens veroudering sowel as frankheid, bitterigheid en mondgevoel. ‘n Wyn se fenoliese samestelling word algemeen bepaal deur wynmaak- en wingerdkundige praktyke. In Suid-Afrika gebeur dit gereeld dat wingerde uitermatig groeikragtig is, wat lei tot te digte lower wat sodoende ‘n negatiewe effek op kwantiteit en kwaliteit van die druiwe wat geproduseer word, het. Wingerdkundige praktyke soos oordeelkundige lowerbestuur en besproeiing is ontwerp om wingerdstokke se groeikrag en opbrengs te beheer, en sodoende vrugrypwording en kleurontwikkeling te verbeter. Kunsmatige beskaduwing en waterstres is gerapporteer om ‘n invloed te hê op die sensoriese eienskappe van rooiwyn sowel as op die flavonoïedsamestelling. Hierdie effekte is egter afhanklik van ‘n verskeidenheid faktore, insluitende die seisoen, kultivar, ligintensiteit en die mate en tyd van waterstres toegepas. Daar is beperkte navorsing op die moontlike interaktiewe effekte van waterstres en lowermanipulasie op die druif en wyn flavonoïedsamestelling in Shiraz, sowel as die verhoudings tussen druif en wyn samestelling. Ons het dus die effekte van lowerbestuur in kombinasie met waterstres op die fenoliese en kleursamestelling van Shiraz druiwe by verskillende rypheidsvlakke ondersoek, asook in hul ooreenstemmende wyne na alkoholieseen appelmelksuurfermentasie sowel as na ses maande veroudering. Hierdie studie het gevind dat dit moontlik is om die fenoliese samestelling van druiwe en wyn deur lootverwydering te verbeter, en sommige van die tendense is ook waargeneem in die wyn na die verouderingsperiode. Indien lootverwydering nie toegepas word by ‘n baie vroeë stadium nie, kan sonbrand voorkom en dit kan lei tot korrels met ‘n laer massa en volume by oes as gevolg van oormatige blootstelling sonder dat die korrel aangepas het by die spesifieke kondisies. Oes by verskillende rypheidsvlakke affekteer ook die chemiese en fenoliese samestelling van die druiwe en ooreenstemmende wyne. Die waterstreseffek op meeste van die fenoliese parameters gemeet in druiwe en wyn was nie so prominent soos dié van die lowermanipulasie behandeling nie. Hierdie studie het ons begrip verbeter van hoe ‘n verbetering van die lower mikroklimaat van Shiraz gereflekteer kan word op die fenoliese samestelling van die wyn, saam met ‘n potensiële belangrike effek van oesdatum. Op grond van hierdie basis is dit dus moontlik om ‘n spesifieke wynstyl te verkry. Oes by ‘n ryp stadium, byvoorbeeld, kan die produksie van wyn met ‘n hoër kleurdigtheid en frankheid tot gevolg hê, terwyl onryp druiwe wyne met hoër vlakke van waarneembare vars bessiekenmerke tot gevolg kan hê. Verlaging van lowerdigtheid kan veral die frankheid en mondgevoel van wyne gemaak van druiwe blootgestel aan waterstres, verbeter.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Chenin blanc wine is of economic importance to South Africa and a range of diverse dry and semi-dry wines are locally produced in this genre. Currently, the use of three distinctly different style names, each aimed at providing consumers with information about the flavour of the wines, is encouraged by the South African (SA) wine industry. The styles are fresh and fruity (FF), rich and ripe unwooded (RRUW) and rich and ripe wooded (RRW). Feedback from retail sectors over the past few years, however, repeatedly suggested that the style names are perceived as confusing by SA consumers. This master study was undertaken to re-evaluate the FF, RRUW and RRW style classification, based on both the volatile fermentation-derived aroma composition and the sensory attributes of a set of wines containing all the styles under investigation. For the purposes of chemical profiling, a set of 105 commercial Chenin blanc wines, selected to be representative of these three styles and originating from the major SA wine producing areas, were analysed by Gas Chromatography (GC) to quantify fermentation-derived volatile aroma compounds in the wines. ANOVA performed on the chemical data showed that 29 compounds represent significant differences between at least two of the 3 styles (FF, RRUW and RRW). Principal component analysis (PCA) of the volatile compounds showed a large degree differentiation between FF and RRW wine styles, however, RRUW wine styles overlapped with the other two styles. Considering vintage effects, ANOVA indicated no significant differences within FF (vintages 2009 and 2010) and RRW (vintages 2008 and 2009) styles, whereas only 2 esters and 4 terpenes showed significant differences between the three wine producing regions investigated for this purpose, Paarl/Wellington, Breede River and Stellenbosch. Volatile aroma compounds generated for Chenin blanc were included in the Winetech database consisting of the most important cultivars of South Africa. Combining the data for the volatiles for Chardonnay and Sauvignon blanc from this database and the data for Chenin blanc obtained in this study, a PCA indicated a clear separation between Chenin blanc and the other two white cultivars. Sensory evaluation of the style classification was done by two separate sensory tests. Firstly, a sorting task was performed by wine industry experts to categorise 21 Chenin blanc wines (FF, RRUW and RRW) based on their similarity. The results showed a differentiation between FF and RRW styles, however, RRUW was mostly classified together with FF wines. This indicated a possible continuum between the three styles, as opposed to three distinct different categories, currently suggested by the style names. The second sensory analysis test, Descriptive Sensory Analysis (DSA), was performed by a trained panel to generate sensory profiles for 42 wines. ANOVA of the flavour attribute intensities between different styles once again showed significant differences between FF and RRW, with RRUW wines forming a continuum between the FF and RRW styles. These results provide valuable information that could be used by the wine industry for labelling purposes. / AFRIKAANSE OPSOMMING: Chenin blanc is van ekonomiese belang vir Suid Afrika en ‘n wye reeks droë en semi-droë wyne word plaaslik geproduseer in hierdie kategorie. Tans word die gebruik van drie duidelike verskillende stylbenamings, elkeen daarop gemik om aan die verbruiker inligting te verskaf oor die geur van die wyn, deur die Suid Afrikaanse (SA) wynindustrie aangemoedig. Die style is vars en vrugtig, ryk en ryp ongehout en ryk en ryp gehout. Terugvoer van die handelssektor oor die afgelope aantal jare, het daarop gedui dat die stylbenamings tot verwarring onder SA verbruikers lei. Hierdie meestersstudie is onderneem om die stylklassifikasie, vars en vrugtig, ryk en ryp ongehout en ryk en ryp gehout, te her-evalueer op grond van die vlugtige aroma komponente wat tydens die fermentasie proses gevorm word, asook die sensoriese eienskappe van ‘n verteenwoordigende stel wyne van elk van die style wat ondersoek is. Vir die doel van die chemiese profilering, is ‘n stel van 105 kommersiële wyne, wat geselekteer is om verteenwoordigend te wees van die drie style ondersoek en ook afkomstig is van die vernaamste SA wynproduserende streke, gebruik. Die wyne is met behulp van gas chromatografie ontleed om die vlugtige komponente wat van die fermentasie proses afkomstig is, te kwantifiseer. Die analise van variansie, het getoon dat 29 komponente statisties beduidend verskil het tussen die drie style. Hoofkomponent analise van die vlugtige komponente, het getoon dat die vars en vrugtige wyne en ryk en ryp gehoute wyne, duidelik onderskeibaar was van mekaar op grond van die vlugtige data, maar die ryk en ryp ongehoute wyne het met die ander twee style oorvleuel. In terme van oesjaar effekte, was daar geen beduidende verskille in die aroma profiele van die vars en vrugtige styl (oesjare 2009 en 2010) en ryk en ryp ongehoute styl (oesjare 2008 en 2009) nie, terwyl die konsentrasie van slegs twee esters en 4 terpene statisties beduidend verskil het tussen die wynproduserende streke Paarl/Wellington, Breederivier en Stellenbosch. Resultate van die gekwantifiseerde vlugtige komponente is in die databasis van Winetech gevoeg, waar die konsentrasies van soortgelyke komponente van die vernaamste SA wynkultivars reeds vervat is. Hoofkomponent analises van die gekombineerde resultate vir Chenin blanc, Chardonnay en Sauvignon blanc wyne, het getoon dat daar ‘n duidelike verkil tussen Chenin blanc en die ander twee wit wynkultivars was. Die sensoriese evaluerings is uitgevoer deur van twee verskillende metodes gebruik te maak. Eerstens is 21 wyne (met al drie style verteenwoordig) deur wynindustrie eksperts gesorteer op grond van die waargenome eendersheid van die onderskeie wyne en die resultate is grafies geprojekteer. Die resultate het getoon dat daar ‘n duidelike verskil waargeneem is deur die assessors tussen die vars en vrugtige styl en ryk en ryp gehoute styl. Die ryk en ryp ongehoute wyne het in die analises meer met die vars en vrugtige style geassosieer, as die ryk en ryp gehoute wyne. Die tweede sensoriese metode is uitgevoer deur sensoriese paneel wat vir die doel van hierdie studie opgelei is om die geur eienskappe van 42 wyne (al drie style verteenwoordig) te profileer. Analise van statistiese beduidende verskille tussen die voorkoms van die geurkomponente en hul intensiteite vir elke styl, het weereens aangedui dat daar ‘n kontinuum bestaan tussen die style. Hierdie resultate kan van waarde vir die wynindustrie wees in besluite rakende etikettering.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Wine fermentation is a continuously changing biological process whereby the raw product, grape juice is transformed into a high value product wine. In an ideal situation the fermentation kinetics of batch fermentations should follow the same trend over time. This however is not the case in industrial wine fermentations where significant batch-to-batch variation is present. The time trajectories of fermentation processes are therefore often unpredictable in absolute terms. The monitoring of substrate (sugar) and product concentrations (ethanol) as well as other quality parameters during a wine fermentation, is therefore of extreme importance to ensure effective control and management of wine fermentation processes. Conventional methods for fermentation monitoring are however costly, time consuming and often unreliable. For these reasons the modern wine industry requires rapid, reliable, non-destructive monitoring techniques which would meet the criteria of providing critical real-time process information that is displayed in easily interpretable graphical format, in order to ensure the highest quality and continuous consistency throughout all the stages of a process. This research study in particular, addressed the current need for alternative fermentation monitoring strategies that meet these criteria, by evaluating the potential use of spectroscopy as an analytical technique for fermentation monitoring. The overall objective of this study was to use chemometric modelling of information obtained by Fourier transform mid-infrared (FT-MIR) and near-infrared (FT-NIR) spectroscopy, to quantitatively and qualitatively monitor both alcoholic (AF) and malolactic fermentation (MLF) processes. Towards this objective 11 batch fermentations elaborated with Oenococcus oeni and Lactobacillus plantarum strains in respectively a co-inoculation and sequential inoculation scenario, were sampled and analysed at regular time intervals with FT-MIR and FT-NIR spectroscopy and enzymatic reference methods during 2011. Samples were also analysed by gas chromatography flame ionisation detection (GC-FID) and mass spectrometry (GC-MS) at two critical stages during fermentation, namely 50% completion of MLF and 100% completion of MLF, in order to obtain a profile of the evolution of the aroma compounds associated with each inoculation scenario. Three clearly defined research objectives were set for this project. The first objective involved the expansion of the existing quantitative platform for fermentation monitoring. Towards the outcomes of this objective, partial least squares (PLS) calibration models for prediction of malic acid and lactic acid in fermenting must and wines elaborated in our study, were established, based on the MIR and NIR spectra. The models showed excellent predictive abilities in independent test set validation. This outcome made a significant contribution to our existing PLS calibration capacity, particularly towards monitoring of MLF. Quantitative data obtained with the PLS models were also used to graphically project the rate of AF in the different batches, by non-linear fitted regression plots that easily visualised the overall patterns of sugar and ethanol metabolism in the different fermentations. The second research objective involved the qualitative monitoring of fermentations. This approach used FT-MIR and FT-NIR spectra together with chemometrics to identify trends between the different fermentation treatments. Principal component analysis (PCA) clearly projected the time trend from the onset of fermentation, through AF and MLF. No unique bacterial trend was however observed with spectroscopy. These results illustrate the potential of these techniques to be used for modelling of fermentations in industrial situations, through providing critical information about the evolution of the process. Furthermore, these techniques provide tools for identifying problematic and deviating fermentations. A spectral conformity test based on simple calculations of the standard deviation between the absorbance at each recorded wavenumber in the spectra, further confirmed identification of the critical fermentation stages. This technique by-passes the need for spectral interpretation and is a very useful addition, particularly from the industry perspective, to the portfolio of methods established in this study. The third research objective adressed the need to evaluate the possibility to discriminate between the different process stages and LAB treatments using univariate (ANOVA) and multivariate chemometric techniques such as PCA, PLS discriminant analysis (PLS-DA) and Soft Independent Modelling of Class Analogy (SIMCA) for possible future interpretative and classification purposes. The exploratory tool of PCA was used to investigate the similarities and differences between the chemical footprints of the different treatments. PCA showed clear differentiation between the two process stages using chemical quantified data. Differentiation between the LAB treatments was visible with PCA, showing a more prominent separation at 50% completion of MLF. Furthermore the ability of spectroscopy for potential classification was shown using PLS-DA and SIMCA. This profiling study can be seen as a preliminary study setting the ground work for further in-depth research into the profiling of different LAB treatments and inoculation strategies. / AFRIKAANSE OPSOMMING: Wyngisting is ‘n voortdurend veranderende biologiese proses waarvolgens die rou produk, druiwesap, in ‘n produk van hoë waarde, naamlik wyn, verander word. Onder ideale omstandighede sou die gistingskinetika van lotgistings dieselfde tendens oor tyd volg. Dit is egter nie die geval in industriële wyngistings nie, waar noemenswaardige wisseling van lot tot lot teenwoordig is. Die tydsbaan van gistingsprosesse is dus in baie gevalle in absolute terme onvoorspelbaar. Die monitering van substraat- (suiker) en produkkonsentrasies (etanol), sowel as ander kwaliteitsparameters tydens ‘n wyngisting, is van die uiterste belang om doeltreffende beheer en bestuur van wyngistingsprosesse te verseker. Konvensionele metodes vir die monitering van gisting is egter duur, tydrowend en ook soms onbetroubaar. Om hierdie redes vereis die moderne wynbedryf vinnige, betroubare en nie-destruktiewe moniteringstegnieke wat aan die kriteria sou voldoen vir die verskaffing van kritiese, intydse prosesinligting wat in ‘n maklik interpreteerbare grafiese formaat vertoon word om die hoogste kwaliteit en voortdurende konsekwentheid tydens al die stadia van ‘n proses te verseker. Hierdie navorsingstudie het in besonder die huidige behoefte aan alternatiewe gistingsmoniteringstrategieë wat aan hierdie kriteria voldoen, aangespreek deur die potensiële gebruik van spektroskopie as ‘n analitiese tegniek vir die monitering van gisting te evalueer. Die oorhoofse doelwit van hierdie studie was die chemometriese modellering van inligting wat met behulp van Fourier transform middel-infrarooi (FT-MIR) en naby-infrarooi (FT-NIR) spektroskopie verkry is om die prosesse van alkoholiese en appelmelksuurgisting (AMG) kwantitatief en kwalitatief te monitor. Ten einde hierdie doelwit te bereik, is 11 lotgistings met Oenococcus oeni en Lactobacillus plantarum rasse uitgevoer in scenario’s van ‘n gesamentlike inokulasie en opeenvolgende inokulasie onderskeidelik. Monsters van hierdie gistings is met gereelde tydintervalle in 2011 geneem en analises is met FT-MIR en FT-NIR spektroskopie en ensiematiese verwysingsmetodes gedoen. Monsters is ook met gaschromatografiese vlam ionisasie-opsporing (GC-FID) en massaspektrometrie (GC-MS) op twee kritiese stadia tydens gisting geanaliseer, naamlik toe AMG 50% en 100% voltooid was, om ‘n profiel te verkry van die evolusie van die aromaverbindings wat met elke inokulasie-scenario verband hou. Drie duidelik gedefinieerde navorsingsdoelwitte is vir hierdie studie bepaal. Die eerste doelwit het die uitbreiding van die bestaande kwantitatiewe platform vir gistingsmonitering behels. Hiervoor is gedeeltelike kleinstekwadraat [partial least squares (PLS)] kalibrasiemodelle vir die voorspelling van appelsuur en melksuur in die gistende mos en wyne in ons studie op die basis van MIR- en NIR-spektra bepaal. Die modelle het in onafhanklike geldigheidsbepaling van die toetsstel uitstekende voorspellingsvermoëns getoon. Hierdie uitkoms het ‘n noemenswaardige bydrae gemaak tot ons bestaande PLS kalibrasiekapasiteit, veral om AMG te monitor. Die kwantitatiewe data wat met die PLS-modelle verkry is, is ook gebruik om die tempo van alkoholiese gisting in die verskillende lotte grafies uit te beeld deur middel van kromlynige passing van regressiepersele, waarmee dit maklik was om die algehele patrone van suiker- en etanolmetabolisme in die verskillende gistings te visualiseer. Die tweede navorsingsdoelwit het die kwalitatiewe monitering van gistings behels. Hierdie benadering het FT-MIR en FT-NIR spektra tesame met chemometrie gebruik om tendense tussen die verskillende gistingsbehandelings te identifiseer. Hoofkomponentanalise [principal component analysis (PCA)] het duidelik die tydtendens vanaf die aanvang van gisting, deur alkoholiese gisting en AMG, geprojekteer. Geen unieke bakteriese tendens is egter met spektroskopie waargeneem nie. Hierdie uitslae illustreer die potensiaal van hierdie tegnieke om vir die modellering van gistings in industriële situasies gebruik te word deur kritiese inligting oor die evolusie van die proses te verskaf. Verder verskaf hierdie tegnieke gereedskap vir die identifikasie van problematiese en afwykende gistings. ‘n Spektrale gelykvormigheidstoets gebaseer op eenvoudige berekeninge van die standaardafwyking tussen die absorbansie by elke aangetekende golfgetal in die spektra het ook die identifikasie van die kritiese gistingstadia bevestig. Hierdie tegniek omloop die noodsaak vir spektrale interpretasie en is ‘n baie nuttige byvoeging tot die portefeulje van metodes wat in hierdie studie bepaal is, veral vanuit ‘n bedryfsperspektief. Die derde navorsingsdoelwit het die behoefte aangespreek om tussen die verskillende prosesstadia en melksuurbakterie-behandelings te onderskei deur gebruik te maak van eenvariant- (ANOVA) en meervariant- chemometriese tegnieke soos PCA, PLSdiskriminantanalise en sagte onafhanklike modellering van klasanalogie [soft independent modelling of class analogy (SIMCA)] vir moontlike toekomstige verklarende en klassifikasiedoeleindes. Die ondersoekende gereedskap van PCA is gebruik om ooreenkomste en verskille tussen die chemiese voetspore van die verskillende behandelings te ondersoek. PCA het duidelike differensiasie tussen die twee prosesstadia getoon op grond van chemies gekwantifiseerde data. Differensiasie tussen die melksuurbakterie-behandelings was met PCA sigbaar, met ‘n meer prominente skeiding teen 50% voltooide AMG. Verder is die vermoë van spektroskopie vir potensiële klassifikasie met PLS-diskriminantanalise en SIMCA getoon. Die profielsamestelling in hierdie studie kan beskou word as ‘n voorlopige studie vir verdere diepgaande navorsing oor die profielsamestelling van verskillende melksuurbakteriebehandelings en inokulasiestrategieë. / The National Research Foundation and Winetech

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Grape must is a complex medium, and during wine production numerous biochemical pathways and metabolic reactions are taking place simultaneously to produce a specific taste and aroma. Microorganisms, specifically yeast, play a key role in the formation of metabolites formed during alcoholic fermentation. Sauvignon blanc, a well studied grape cultivar, is known to have a versatile range of aroma profiles ranging from “green” to “tropical”. It has been broadly stated that a “green” Sauvignon blanc can be created in the vineyard and a “tropical” Sauvignon blanc can be created by selecting a specific yeast strain, and that the balance between “green” and “tropical” characters is essential for the final aroma profile. Except for grape-derived varietal aromatic compounds such as methoxypyrazines (green), volatile thiols (tropical) and monoterpenes (floral), yeast derived volatile compounds including esters, higher alcohols, fatty acids and carbonyl compounds will also contribute to the final wine aroma. The main aim of this study was to assess how viticultural treatment-derived differences in grape must, can impact on aroma production when this grape must is fermented with different commercial wine yeast strains. The viticulture treatment focused on light intensity modulated through canopy treatment. Volatile aroma differences were compared for canopy and yeast treatments, specifically focusing on the fermentation derived bouquet (esters, higher alcohols, volatile fatty acids, carbonyl compounds and monoterpenes). Results showed significant differences between initial must compositions, including titratable acidity, malic acid and yeast assimilable nitrogen. The volatile aroma compounds were also significantly impacted although no noticeable effect on the overall fermentation kinetics was observed. Depending on the yeast strain differences in volatile compounds varied. A clear vintage effect is noticeable between volatile compounds affected by the treatments. Data generated in 2012 shows clear differences between ethyl- and acetate esters and could clearly be grouped according to yeast strain through multivariate analysis. Sensory evaluation results could clearly be distinguished according to canopy treatment and to a lesser degree according to yeast strain used. This indicates that although yeast has a more prominent impact on the fermentative bouquet that develops during alcoholic fermentation the overriding aroma is primarily derived from grape-derived metabolites which can be manipulated by canopy treatments. None the less the difference in fermentation bouquet does add to the complexity of the wine especially in the case of fermentation derived “tropical” aromas including guava and passion fruit. In some cases where shaded grapes had higher ester concentrations, the resultant wine also had higher aroma quality. This study has contributed to a better understanding of the complex relationships between canopy manipulation and yeast selection on aroma formation. The analysis of volatile aroma alone however is not enough to understand the final perception of wine taste and further indepth studies of the viticultural and oenological factors is needed. In particular, this project has focused on a single vineyard over only two vintages. The general validity of the conclusions derived from this study therefore will require additional data sets. / AFRIKAANSE OPSOMMING: Druiwemos is ‘n komplekse medium en tydens wynbereiding is daar verskeie biochemiese weë en metaboliese reaksies wat gelyktydig plaasvind om ‘n spesifieke smaak en aroma te produseer. Mikro-organismes, veral gis, speel ‘n sleutelrol in die vorming van metaboliete tydens alkoholiese gisting. Sauvignon blanc, ‘n goed bestudeerde druifkultivar, besit ‘n veelsydige reeks aromaprofiele wat wissel van “groen” tot “tropies”. Oor die algemeen word dit voorgehou dat ‘n “groen” Sauvignon blanc in die wingerd geskep word, terwyl ‘n “tropiese” Sauvignon blanc geskep kan word deur ‘n spesifieke gisras te selekteer, en die balans tussen “groen” en “tropiese” karakters is noodsaaklik vir die finale aromaprofiel. Behalwe vir druifafgeleide kultivarafhanklike aromatiese verbindings soos metoksipirasiene (groen), vlugtige tiole (tropies) en monoterpene (blomagtig), sal gisafgeleide vlugtige komponente, waaronder esters, hoër alkohole, vetsure en karbonielverbindings, ook tot die finale wynaroma bydra. Die hoofdoelwit van hierdie studie was om te bepaal hoe verskille in druiwemos wat afkomstig is van wynkundige behandeling ‘n impak op aromaproduksie kan hê wanneer hierdie druiwemos met verskillende kommersiële wyngisrasse gegis word. Die wynkundige behandeling het gefokus op ligintensiteit wat deur lowerbehandeling gereguleer is. Vlugtige aromaverskille is op grond van lower- en gisbehandelings vergelyk, met ‘n spesifieke fokus op die gistingsafgeleide boeket (esters, hoër alkohole, vlugtige vetsure, karbonielverbindings en monoterpene). Die resultate het beduidende verskille getoon tussen aanvanklike mossamestellings, waaronder titreerbare suurheid, appelsuur en gis-assimileerbare stikstof. Daar was ook ‘n noemenswaardige impak op die vlugtige aromaverbindings, hoewel geen merkbare effek op die algehele gistingskinetika waargeneem kon word nie. Die verskille in vlugtige verbindings het gewissel op grond van die gisras. ‘n Duidelike oesjaareffek was merkbaar tussen vlugtige verbindings wat deur die behandelings geaffekteer is. Data wat in 2012 gegenereer is, toon duidelike verskille tussen etiel- en asetaatesters en kon duidelik m.b.v. meervariantanalise volgens gisras gegroepeer word. Die resultate van die sensoriese evaluering kon duidelik volgens lowerbehandeling onderskei word, en tot ‘n mindere mate volgens die gisras wat gebruik is. Dít dui daarop dat hoewel gis ‘n meer prominente impak het op die gistingsboeket wat tydens alkoholiese gisting ontwikkel, is die oorheersende aroma hoofsaaklik afgelei van druifafgeleide metaboliete wat deur lowerbehandelings gemanipuleer kan word. Nietemin dra die verskil in gistingsboeket by tot die kompleksiteit van die wyn, veral in die geval van gistingsafgeleide “tropiese” aromas, insluitend koejawel en grenadella. In sommige gevalle waar beskadude druiwe hoër esterkonsentrasies gehad het, het die gevolglike wyn ook ‘n hoër aromakwaliteit gehad. Hierdie studie dra by tot ‘n beter begrip van die effek van die komplekse verhoudings tussen lowermanipulasie en gisseleksie op aromavorming. ‘n Analise van vlugtige aroma alleen is egter nie voldoende om die finale persepsie van wynsmaak te begryp nie en bykomende diepgaande studies van die wingerdkundige en wynkundige faktore word benodig. Hierdie projek het in die besonder gefokus op ‘n enkele wingerd oor slegs twee oesjare. Die algemene geldigheid van die afleidings wat van hierdie studie gemaak word, sal dus bykomende datastelle vereis. / The National Research Foundation and Postgraduate Merit Bursary for financial support

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The quality of wine is largely dependent on environmental conditions and recent studies have therefore focused on agricultural practices in terms of water, soil and biodiversity conservation. The industry aims to create sustainable practice and to protect the natural resources available. Sources of potential grape contamination include: vehicle pollution, pesticides, bushfires and wood preservatives used for trellising systems. The latter have come to the attention of the South African wine industry (e.g. creosote and Copper Chromium Arsenate (CCA) products) as they may have consequences for the environment and wine quality. Creosote is a known pollutant of soil and ground water and the volatile fraction has been monitored in air. Plants may also accumulate polycyclic aromatic hydrocarbons (PAHs), which constitute up to 85% of the mass of creosote, and of which some have been proven carcinogenic. Because of the health risks associated with it, creosote has therefore been restricted for use in most applications in Europe, and also in the United States, Canada and Australia. This study focussed on the sensorial and chemical analyses of environmental and wine samples taken from the area around the creosote stockyard to determine accumulation of creosote-derived compounds. Environmental samples were collected and analysed at different distances from the affected area, over two vintages. Wines were made from grapes grown in vineyard blocks adjacent to the stockyard, to determine the effect of distance and skin contact during alcoholic fermentation treatments on wine taint. A sensory panel was trained for descriptive analysis to determine the intensity of the taint. Analytical methods were developed for the analysis of volatile organic compounds (VOCs) by gas chromatography mass spectrometry (GC-MS) and polycyclic aromatic hydrocarbons by high performance liquid chromatography with diode array detection (HPLC-DAD). The sensory results obtained showed white and rosé wines were perceived as clean, whilst the red wines were associated with burnt rubber/tar taint. The perceived taint decreased as distance from the stockyard increased. Wines made from the Cabernet Sauvignon blocks adjacent to the stockyard also showed an increase of taint with the increase of skin contact. Chemical data obtained showed that the taint consisted of a complex mixture of compounds, each with its own pattern of retention within the vineyard and wine. Only m-cresol was found above odour threshold, and only in red wines. The synergistic effect of some compounds may lead to an increase in the perceived taint. Berries and leaves had higher concentrations of volatile compounds than wines. Leaf contamination varied and followed the general trend in literature where the plants with high lipid content and exposed leaf area were the most contaminated. There may be other compounds present in creosote emissions, aside from those investigated here, with sensory attributes related to the taint found in wines. These compounds are styrene, indene, benzene, toluene, isoquinoline and quinoline and should be included in further investigations. From the PAH analysis of environmental samples and wines, it is evident that the samples closest to the stockyard were affected the most. The contamination varied with the depth of the soil: some of the heavier compounds were found in the samples taken from the deeper levels, whilst nearly all other target compounds were present in the top layer of soil. The concentrations found in the environmental samples were lower than reported in literature. Wines had few PAHs present, but at much higher concentrations than is allowed by EU legislation. From this study it is evident that the stockyard had negative effects on the surrounding environment in terms of sensory and chemical contamination. Recommendations include area rehabilitation by means of bioremediation to protect resources and ensure sustainable and safe production of crops. Industrial emissions should also be regulated and restricted in agricultural areas. Furthermore the use of creosote should be revised, and prohibited for agricultural use. / AFRIKAANSE OPSOMMING: Die kwaliteit van wyn is grootliks afhanklik van die omgewingstoestande. Daarom fokus verskeie onlangse studies op landbou aktiwiteite en die invloed daarvan op die omgewing in terme van water, grond en biodiversiteit bewaring. The wyn industrie se doelwitte sluit volhoubare praktyke in, wat die natuurlike hulpbronne bewaar en beskerm. Druiwe kan deur middel van die volgende bronne besoedel word: brandstof uitlaatgasse, insekdoders, veldbrande, gifstowwe wat gebruik word vir houtperservering wat dan verder aangewend word vir opleistelsels. Houtperservering (Koper chroom arsenaat (CCA) en kreosoot) het veral in die laaste paar jaar onder aandag gekom in die wynbedryf van Suid-Afrika as gevolg van die invloed daarvan op die omgewing en die uiteindelike wynkwaliteit. Kreosoot is ‘n gekende gifstof wat verantwoordelik is vir grond en grondwater besoedeling en wat gemonitor word in die atmosfeer. Plante akkummuleer ook poli-sikliese aromatiese hidro-koolstowwe (PAHs), wat to 85% uitmaak van die massa van kreosoot. PAHs is karsinogenies en dus is daar baie navorsing op die molekules reeds gedoen. Die gesondheidsrisikos gepaardgaande met kreosoot het gelei tot die streng geregulasies tans ingestel in Europa, die Verenigde State, Kanada en Australië. Hierdie studie het gefokus op die sensoriese en chemiese analises van omgewings- en wyn-monsters geneem van die omliggende area van die kreosoot palewerf om die akkumulasie van kreosoot-afgeleide-verbindings. Omgewingsmonsters was versamel en geanaliseer om verskillende afstande vanaf die bron van besoedeling (palewerf) te ondersoek oor ‘n twee jaar periode. Wyne is gemaak van die druiwe wat afkomstig is van die blok aangeplant langs die palewerf. Die wyne is ondersoek in terme van afstand vanaf die kreosoot bron asook oenologiese invloede, dopkontak gedurende alkoholiese fermentasie, op die kontaminasie beskryf in wyn. Die wyne is ook oor ‘n twee jaar periode voorberei en sluit die 2011 en 2012 seisoen in. ‘n Sensoriese paneel is opgelei om die beskrywende analises op die wyn uit te voer met die doel om die intensiteit van kontaminasie te identifiseer. Analitiese metodes is ook ontwikkel vir die analise van vlugtige organiese verbindings(VOCs) met gas chromatografie-massa spektrometrie (GCMS) en poli-sikliese aromaties hidro-koolstowwe (PAHs) met hoë druk vloeistof chromatografie. Die sensoriese resultate bekom het wit en rosé wyne as skoon laat blyk, terwyl rooi wyne meer geassosieer was met die gebrande rubber/ teer afgeur beskrywing. Die waargeneemde afgeur het afgeneem soos wat die afstand vanaf die palewerf toegeneem het. Wyne gemaak van die Cabernet Sauvignon blokke langsaan die palewerf het ook ‘n toename in die afgeur gehad met ‘n toename in dopkontak. Chemiese data bekom beeld uit dat die afgeur uit ‘n komplekse mengsel van verbindings bestaan, elk met sy eie patroon van verspreiding en verbinding in die wingerd as ook in die wyn. Net m-kresol was gevind bo die reuk drumpel, dit het ook net in rooi wyne voorgekom. Die sinergistiese effek van die verbindings mag egter bydra tot die waargeneemde afgeur. Druiwekorrels en blare het hoër konsentrasies van die vlugtige verbindings gehad as wat gemeet is in die wyne. Blaar kontaminasie het ook baie gewissel en het ooreengestem met die algemene tendens wat in literatuur beskryf is, naamlik dat plante met ‘n hoër lipid inhoud en grootter blaar oppervlak die meeste gekontamineer word. Daar mag egter nog baie ander verbindings bydra tot die waargeneemde afgeur gevind in die wyn. Spesifieke verbindings wat wel ‘n rol kan speel in kontaminasie en wat voorkom in die vlugtige gedeelte van kreosoot is styreen, indeen, benzeen, tolueen, isoquinoleen die vlugtige verbindings van kreosoot. Die verbindings moet ingesluit word vir verdere studies wat gedoen word op die kreosoot geassosieerde afgeur. Die PAHs analise op die omgewingsmonsters en wyne het gelei tot die bevestiging dat die naasliggende omgewing die meeste geaffekteer is. Die kontaminasie wissel in terme van die diepte in die grond wat die gifstowwe voorkom: die swaarder molekulêre verbindings is tot in die dieper vlakke waargeneem terwyl al die gemete verbindings in die boonste lae teenwoordig was. Die vlakke wat waargeneem is in dié studie is egter laer as wat voorheen in literatuur gevind is in ‘n kreosoot geaffekteerde omgewing. Wyn het PAHs teenwoordig gehad, alhoewel slegs twee verbindings gemeet is, het dit in hoër vlakke voorgekom as wat sekere Europese regulasies as toelaatbaar spesifiseer. Vanaf die studie resultate blyk dit, dat die palewerf se negatiewe invloed op die omliggende omgewing beide meetbaar was in sensories en chemiese kontaminasie. Voorstelle sluit onder andere die rehabilitasie van die omliggende omgewing deur middel van bioremediasie in. Om sodoende die natuurlike hulpbronne in die area te bewaar asook om volhoubare en veilige verbouing van gewasse te verseker. Industriële besoedeling en afval moet ook gereguleer word en beperk word in landbou areas. Verder moet die gebruik van kreosoot heroorweeg word en strenger regulasies moet in plek gestel word om aan internastionale standaarde te voldoen. / Financial support from Winetech, Trip and UFS

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The influence of malolactic fermentation (MLF) in most red and some white wines is one of many factors that determine or influence wine quality, because it affects the flavour and sensory profile of wine. This process is a decarboxylation process conducted by lactic acid bacteria (LAB) such as Oenococcus, Lactobacillus, Pediococcus and Leuconostoc. Mostly Oenococcus oeni, but recently also Lactobacillus plantarum is used in commercial starter cultures and also the first mixed MLF starter culture (NT 202 Co-Inoculant) was commercialized in 2011. The reason for the predominant use of O. oeni and recently L. plantarum is due to their tolerance to the harsh wine environment. Malolactic fermentation leads to a decrease in acidity and an increase in pH that leaves the wine with a softer mouthfeel. Another reason to conduct MLF is the improvement of microbial stability by the removal of malic acid as carbon source. Research focus has recently shifted to the ability of LAB and MLF as well as the interaction of LAB with yeast to alter the wine aroma profile via the modification and/or production of certain aroma compounds. The main goal of this study was to assess the impact of yeast and nutrient addition on the ability of the NT 202 Co-Inoculant to conduct MLF during co-inoculation and to evaluate the aroma compound production in the final wine. The first aim was to evaluate the impact of different red and white wine yeast strains on the ability of the NT 202 Co-Inoculant to conduct MLF during co-inoculation in Chardonnay, Merlot and Shiraz. Malolactic fermentation was unsuccessful in the Chardonnay due to a low pH, but successful in Merlot and Shiraz. Based on the malic acid degradation ability of the NT 202 Co- Inoculant, the yeasts were grouped into three categories: inhibitory, neutral or stimulatory towards MLF. Co-inoculated MLF showed a clear decrease in total fermentation time while yeast strains such as WE 372 and Exotics showed positive compatibility with the NT 202 Co- Inoculant. The impact of the yeast-bacterial combinations on the aroma compound production in the final wine was evaluated. Co-inoculated MLF showed positive aroma changes in the red wines with a general increase in total esters (associated with fruity characters in wine) especially ethyl lactate and diethyl succinate that also contribute to the mouthfeel of the wine. Production of esters, volatile fatty acids and higher alcohols seemed to depend on the yeastand LAB strain used. The NT 202 Co-Inoculant contributed to the monoterpenes produced and MLF led to increased concentrations of diacetyl and acetoin, which are associated with buttery characters in wine. The second aim of this study was to evaluate the impact of wine additives (used during coinoculation) such as yeast- and bacterial nutrients, clarifying- and detoxifying agents on the ability of the NT 202 Co-Inoculant to conduct MLF and to assess their impact on the aroma compound production in the final wine. No negative or positive impact on the malic acid degradation of the NT 202 Co-Inoculant or the resulting aroma compound production was observed for the different wine additives used in this study. The results generated from this study showed that the selection of yeast strains is important as it will influence both the fermentation duration and final wine aroma. / AFRIKAANSE OPSOMMING: Die invloed van appelmelksuurgisting (AMG) in die meeste rooi- en witwyne is een van baie faktore wat wynkwaliteit beïnvloed, omrede dit die geur en sensoriese profiel van wyn beïnvloed. Hierdie proses is 'n dekarboksileringsaksie wat deur melksuurbakterieë (MSB), soos Oenococcus, Lactobacillus, Pediococcus en Leuconostoc, uitgevoer word. Die mees algemene bakterieë wat gebruik word, is Oenococcus oeni, maar onlangs het Lactobacillus plantarum ook na vore getree in die gebruik van kommersiële aanvangskulture. Die eerste gemengde AMGaanvangskultuur (NT 202 Co-Inoculant) is in 2011 gekommersialiseer. Die rede vir die oorheersende gebruik van O. oeni en L. plantarum word toegeskryf aan hul gehardhiedsgraad in ‘n uitdagende wynomgewing. Appelmelksuurgisting lei tot 'n afname in die suurheidsgraad en 'n toename in die pH van die wyn, wat 'n sagter mondgevoel tot gevolg het. Nog 'n rede waarom AMG deurgevoer word, is om die mikrobiese stabiliteit van die wyn te verbeter deur die verwydering van appelsuur as koolstofbron. Die navorsingsfokus het onlangs verskuif na die vermoë van MSB en AMG, sowel as die interaksie van MSB met die gis, om die wynaromaprofiel te verander deur middel van die verandering en/of produksie van sekere aromaverbindings. Die hoofdoel van hierdie studie was om die impak van die gis en voedingstof te evalueer ten opsigte van die vermoë van die NT 202 Co-Inoculant om AMG uit te voer tydens koïnokulasie. Die produksie van aromakomponente in die finale wyn is ook geëvalueer. Die eerste doelwit was om die impak van verskillende rooi- en witwyngisrasse te evalueer ten opsigte van die vermoë van die NT 202 Co-Inoculant om AMG uit te voer tydens koïnokulasie in Chardonnay, Merlot en Shiraz. Appelmelksuurgisting was onsuksesvol in die Chardonnay weens 'n lae pH, maar suksesvol in Merlot en Shiraz. In terme van die appelsuurafbraakvermoë van die NT 202 Co-Inoculant, is die giste in drie kategorieë gegroepeer: inhiberend, neutraal of stimulerend teenoor AMG. Ge-koïnokuleerde AMG het 'n duidelike afname in die totale fermentasietyd getoon, terwyl gisrasse, soos WE 372 en Exotics, ‘n positiewe verenigbaarheid met die NT 202 Co-Inoculant getoon het. Die impak van die gisbakteriële kombinasies op die aromakomponentproduksie in die finale wyn is geëvalueer. Gekoïnokuleerde AMG het positiewe aromaveranderinge in die rooiwyne getoon met 'n algemene toename in die totale esters (wat geassosieer word met vrugtige karakters in wyn), veral etiellaktaat en dietielsuksinaat, wat ook bydra tot die mondgevoel van die wyn. Dit het voorgekom dat produksie van esters, vlugtige vetsure en hoër alkohole moontlik afhanklik kan wees van die gis- en bakteriële ras gebruik. Die NT 202 Co-Inoculant het bygedra tot die monoterpene wat geproduseer is en AMG het gelei tot verhoogde konsentrasies van diasetiel en asetoïen, wat geassosieer word met botteragtige karakters in wyn. Die tweede doelwit van hierdie studie was om die impak van wyntoevoegingsmiddels (wat tydens koïnokulasie gebruik word) bv. gis- en bakteriese voedingstowwe, verhelderingsagente, asook detoksifiserende agente, te evalueer ten opsigte van die vermoë van die NT 202 Co- Inoculant om AMG uit te voer en om hul impak op die produksie van die aromakomponente van die finale wyn te ontleed. Geen negatiewe of positiewe effekte is waargeneem vir die verskillende wyntoevoegingsmiddels, wat in hierdie studie gebruik is, in terme van die appelsuurafbraak van die NT 202 Co-Inoculant of die gevolglike produksie van aromakomponente nie. Hierdie studie se resultate toon dat die keuse van die gisras belangrik is, omdat dit die fermentasietydperk, asook die finale wynaroma, beïnvloed. / Anchor Yeast, Oenobrands, The National Research Foundation and THRIP, for financial support