Thesis (MScAgric)--Stellenbosch University, 1969. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In the present-day competitive global market, wine industries are constantly aiming to improve the wine-making process,including the role of yeast. The most commonly used wine yeast is Saccharomyces cerevisiae, which is able to produce high quality wines, but problem fermentations do sometimes arise. The occurrence of stuck and sluggish fermentations pose a serious problem leading to loss of productivity and quality. Although the precise mechanism leading to stuck fermentations is unknown, they are often correlated with high fructose to glucose ratios in the wine-must. S. cerevisiae is a glucophylic yeast, indicating its preference for consuming glucose over fructose. Both these hexose sugars are present in unfermented wine must, mostly in equal concentrations. As fermentation progresses, glucose is consumed at a faster rate than fructose, leading to an increase in the fructose to glucose ratio. Yeast are left with the undesirable fructose at the later stages of fermentation, when the environmental stresses on the yeast can lead to stuck or sluggish fermentation. This residual fructose can lead to undesirable sweetness, as fructose is about twice as sweet as glucose. Even with the extensive research into yeast metabolism, there is as yet no definitive explanation as to why yeasts ferment glucose faster than fructose. This study aimed to investigate the mechanism responsible for the faster consumption of glucose over fructose of a commercially used wine yeast strain S. cerevisiae VIN 13. The first two steps of sugar metabolism, uptake and phosphorylation, were investigated as the possible sites of discrepancy in fermentation rates. Enzyme rates and affinities for both glucose and fructose as substrates for the relevant enzymes were experimentally determined. These kinetic parameter values were used to improve an existing model of yeast glycolytic pathway to model wine fermentations. The feasibility of constructing and validating a kinetic model of wine fermentations were investigated, by comparing model predicted fluxes with experimentally determined fluxes. Another aspect of this study was an investigation into the effect of hexose sugar type on fermentation profiles. Wine fermentations were done with only one hexose sugar as carbon source to determine if it has an effect on the flux through metabolism. This work succeeded in the construction of a kinetic model that distinguished between glucose and fructose as carbon source. The glucose was consumed faster than fructose, with control lying in the hexose transport step. It was also established that fermentation prfiles of fermentations with only one sugar was the same for both one sugar type fermentations. Fermentation with either glucose or fructose as the sole carbohydrate source had the same specfic production and consumption rates as normal fermentations with both sugars. Construction of detailed kinetic models can aid in the metabolic and cellular engineering of novel yeast strains. By identifying the importance of hexose transport, and thus the glucophilic character of the yeast, in flux control, yeast transporters can be targeted for strain improvement. This may in turn lead to more effective fermentation practices for controlling problem fermentations, or to the development of novel strains that utilizes fructose in the same manner as glucose, and in so doing lower the risk of stuck or sluggish wine fermentation. / AFRIKAANSE OPSOMMING: In die hedendaagse kompeterende wynmark is wynmakers aanhoudend besig om die wynmaak proses te verbeter en dit sluit die verbetering van wyngis in. Die mees algemeenste gebruikte wyngis is Saccharomyces cerevisiae, omdat dit wyn van gehalte produseer, maar probleem fermentasies kom wel voor. Die verskynsel van vasval of stadige fermentasies kan lei tot die verlies van produksie en kwaliteit. Die oorsaak van probleem fermentasies is gewoontlik veelvoudig, maar die verhouding van glukose tot fruktose in die wyn-mos kan ongunstig raak om fermentasies te onderhou. S. cerevisiae is 'n glukofiliese gis, wat sy voorkeur om glukose bo fruktose te gebruik beskryf. Albei hierdie heksose suikers is teenwoordig in ongefermenteerde wyn-mos, meestal in gelyke hoeveelhede. Soos fermentasies vorder word glukose vinniger verbruik as fruktose wat lei tot 'n toename in die fruktose tot glukose verhouding. Die gis moet dus die fruktose in die later stadium van fermentasie gebruik wanneer die omgewings druk op die gis kan lei tot probleem fermentasies. Die oorblywende fruktose kan lei tot ongewenste soetheid aangesien fruktose twee keer soeter is as glukose. Selfs met die ekstensiewe navorsing met betrekking tot gis metabolisme is daar nog nie 'n verduideliking hoekom gis glukose vinniger as fruktose gebruik nie. Hierdie studie het beoog om die meganisme wat lei tot die vinniger verbruik van glukose oor fruktose te ondersoek vir 'n kommersieël gebruikte gis S. cerevisiae VIN 13. Die eerste twee stappe van suiker metabolisme, suiker opname en fosforilasie, was ondersoek as die moontlike punt van die verskil in fermentasie tempo. Ensiem snelhede en affiniteite vir beide glukose en fruktose as substrate vir die ensieme van belang was eksperimenteel bepaal. Hierdie waardes is gebruik om 'n bestaande model van gis glikolise aan te pas vir wyn fermentasies. Die uitvoerbaarheid van saamstel en valideer van 'n kinetiese model van wyn fermentasies was ondersoek, deur model voorspelde fluksie waardes met eksperimentele fluksie waardes te vergelyk. 'n Ander aspek van die studie was die ondersoek van die effek van heksose suiker tipe op fermentasie profiel. Wyn fermentasies is gedoen met slegs een heksose suiker as koolstof bron om te bepaal of dit 'n invloed het op die fluksie deur metabolisme. Hierdie werk het daarin geslaag om 'n kinetiese model saamtestel wat onderskei tussen glukose en fruktose as koolstof bron. Die glukose is vinniger verbruik as fruktose, met beheer gesetel in die heksose opname stap. Dit was ook vasgestel dat fermentasie profiele van fermentasies met slegs een suiker nie verskil het vir fermentasies met slegs fruktose of glukose. Fermentasies met slegs een suiker het dieselfde spesifieke produksie en konsumpsie tempo gehad as die normale fermentasie met albei suikers. Die konstruksie van 'n gedetailleerde kinetiese model kan gebruik word in die metaboliese en sellulêre ontwikkeling van nuwe gisstamme. Deur die ontdekking van die belangrikheid van heksose opname in fluksie beheer, wat lei tot die glukofiliese karakter van gis, kan gis opname geteiken word vir gis ontwikkeling. Dit mag om die beurt lei tot meer effektiewe fermentasie praktyk in die beheer van probleem fermentasies, of die ontwikkeling van nuwe stamme wat fruktose in dieselfde manier as glukose benut, en sodoende die risiko van vasval of stadige wyn fermentasies verlaag. / National Research Foundation / Post-graduate Merit Bursary

Thesis (MSc)--Stellenbosch University, 1959. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2008. / A method for the detection of adulteration of South African Sauvignon blanc wines, by enrichment with foreign sources of 3-alkyl-2-methoxypyrazenes, is described. The levels of three 3-alkyl-2-methoxypyrazenes (3-isobutyl-, 3- isopropyl- and 3-sec-butyl-2-methoxypyrazine) in South African Sauvignon blanc wines were measured with liquid chromatography-mass spectrometry. Sample preparation involved clean-up and pre-concentration by distillation followed by solvent extraction of the distillate with dichloromethane. Extracts were acidified and concentrated by evaporation and finally reconstituted to a fixed volume to affect quantitative pre-concentration of the samples. Sample extracts were separated with reversed phase liquid chromatography utilizing a phenyl-hexyl separation column. Residues were measured with liquid chromatography-mass spectrometry utilizing a tandem quadrupole mass spectrometric detector operated in multiple reaction monitoring mode for optimal trace level quantitation. Atmospheric pressure chemical ionization was utilized as electrospray ionization was found to suffer from quenching effects attributed to the sample matrix. Qualitative information was obtained from the relevant molecular ions as well as two secondary ion transitions (and one ion ratio) in each case. Recoveries obtained by the extraction procedure were better than 90% with coefficient of variance of better than 10% at concentrations from 1 to 100 ng/L. The limit of detection of the method was 0.03 ng/L and the limit of quantification 0.10 ng/L for the three analytes measured. The described LC-MS method is more sensitive for the determination of 3-alkyl-2-methoxypyrazines in wine than GC methods reported for the same purpose. From the experimental data, a set of parameters were established to discriminate adulterated South African Sauvignon blanc wines. It was demonstrated that the 3-isobutyl-2-methoxypyrazine concentration, despite showing considerable variance, was confined to a relatively narrow range spanning approximately two orders of magnitude (0.20 to 22 ng/L). A clear indication of possible maximum values for this compound in South African Sauvignon blanc wines was obtained from the analysis of a large number of samples (577), spanning most relevant wine producing regions and representing vintages 2003 to 2006. It was also demonstrated that South African Sauvignon blanc wines contain the major 3- alkyl-2-methoxypyrazenes in reasonably distinct relative amounts and that the said ratios of abundance may be used to elucidate authenticity. The expected effect of adulteration with green pepper extracts or some synthetic preparations on the 3-isobutyl-2-methoxypyrazine concentration as well as the relative abundances were also determined by characterizing the corresponding profiles in green peppers and some synthetic flavor preparations. Two adulterated samples in the dataset were identified by both outlined criteria. A limited number of wines of other cultivars were also analyzed. The results represent the most complete and accurate data on the 3-alkyl-2-methoxypyrazine content of South African Sauvignon blanc wines to date. A publication covering the work presented in this thesis is currently in preparation.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Wine quality is compromised by the presence of 3-hydroxypropionaldehyde (3-HPA) due to spontaneous conversion into acrolein under wine making conditions. Acrolein is highly toxic and is presence has been correlated with the development of bitterness in wine. Lactic acid bacterial strains isolated from South African red wine, Lactobacillus pentosus and Lactobacillus brevis, are implicated in accumulating 3- HPA during anaerobic glycerol fermentation. The environmental conditions leading to its accumulation are elucidated. In aqueous solution 3-HPA undergoes reversible dimerization and hydration, resulting in an equilibrium state between different derivatives. Interconversion between 3-HPA derivatives and acrolein is a complex and highly dynamic process driven by hydration and dehydration reactions. Acrolein is furthermore highly reactive and its steady-state concentration in complex systems very low. As a result analytical detection and quantification in solution is problematic. This study highlights the roles played by natural chemical derivatives and shows that the acrolein dimer can be used as a marker for indicating the presence of acrolein in wines. Solid-phase microextraction (SPME) coupled to gas chromatograph mass spectrometry (GC-MS) was validated as a technique for direct detection of the acrolein dimer in wine. The potential of a recently introduced sorptive extractive technique with a sample enrichment probe (SEP) was also investigated. The SPME technique simplifies the detection process and allows for rapid sampling of the acrolein marker, while SEP is more sensitive. / AFRIKAANSE OPSOMMING: Die teenwoodigheid van 3-hidroksiepropioonaldehied (3-HPA) in wyn het ‘n negatiewe invloed op kwaliteit as gevolg van die moontlike omskakeling na akroleien tydens die wynmaak prosses. Akroleien is hoog toksies en is moontlik betrokke by die ontwikkeling van ‘n bitter komponent in wyn. Hierdie studie wys dat stamme van die melksuurbakteriëe Lactobacillus pentosus en Lactobacillus brevis, geisoleer uit Suid-Afrikaanse wyn, 3-HPA tydens anaerobiese alkoholiese fermentasie kan opbou. Kondisies wat ontwikkeling beinvloed is bestudeer. 3-HPA ondergaan omkeerbare dimerisasie en hidrasie in oplossing en het ‘n ewewig tussen veskillende derivate tot gevolg. Omkakeling tussen 3-HPA derivate en akroleien is ‘n komplekse en hoogs dinamiese prosses wat gedryf word deur hidrasie en dehidrasie reaksies. Akroleien is verder hoogs reaktief en die ewewigskonsentrasie van hierdie aldehied in komplekse omgewings is laag. Analitiese waarneming en kwantifisering is gevolglik problematies. Hierdie studie lig die rol wat natuurlike chemise derivate speel duidelik uit en wys dat die akroleien dimeer as ‘n merker gebruik kan word om die teenwoodigeid van akoleien in wyn te staaf. Soliede-fase mikro-ekstraksie (SPME) gekoppel aan gas chromatografie massa spektroskopie (GC-MS) is gevalideer as ‘n tegniek vir die direkte waarneming van die akroleien dimeer in wyn. Die potensiaal van ‘n nuwe ekstraksie tegniek, gebasseer op ‘n peiler wat vir die monster verreik (SEP), was ook ondersoek. Die SPME tegniek is vinnig en vergemaklik analiese, terwyl SEP meer sensitief is.

Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: In the highly competitive international wine markets, effective procurement of raw material could prove the difference between success or failure for a wine company. Therefore the researcher embarked on this study to create a model that will assist procurement decision makers in the South African wine industry in the strategic procurement of raw material. In order to create a model for procurement of raw material in the South African wine industry, qualitative research was conducted that included a study of literature, available material, views from experts as well as a content analysis from sample interviews. Procurement officials need to ensure that marketing forecasts are aligned with contracted procurement volumes. Cost, quality and availability should be tightly managed to minimise losses due to unallocated inventory or lack of raw material with sufficient quality or quantity to serve a marketing need. Suppliers should be prioritised in terms of strategic importance and procurement decision-makers should be crystal clear on which strategy to pursue with each quality segment and supplier in order to obtain the right quantity at the desired quantity and most economical price. Procurement decision makers need to evaluate the procurement and market environment for opportunities and threats that might impact on their ability to procure raw material from their supply base, and put measures in place to take control of possible effects of those uncertainties. This includes differentiating between grape procurement and wine procurement to leverage the advantages from both. Procurement officials must establish an action plan to limit the risk of cost, availability and quality by engaging and investing in trusting, loyal relationships with proficient suppliers with capacity. The procurement function should operate in a professional manner, building a track record of pro-active procurement and focus on loyal supplier relationships. / AFRIKAANSE OPSOMMING: In die hoogs kompeterende internasionale wynmarkte kan effektiewe aankope van rou-materiaal die verskil beteken tussen sukses of mislukking vir 'n wynmaatskappy. Daarom het die navorser begin met hierdie studie om 'n model te skep wat besluitnemers van aankope kan bystaan met die strategiese aankoop van roumateriaal in die Suid-Afrikaanse wynbedryf. Om 'n model te skep vir die aankoop van roumateriaal in die Suid-Afrikaanse wynbedryf is kwalitatiewe navorsing gedoen, wat 'n literatuurstudie insluit, sowel as 'n studie van beskikbare materiaal, sienings van kenners en 'n inhoudsanalise van steekproefonderhoude. Aankoopsbeamptes moet verseker dat bemarkingsvooruitskattings en gekontrakteerde aankoopvolumes ooreenstem. Koste, kwaliteit en beskikbaarheid moet streng bestuur word om verliese te beperk wat kan ontstaan deur ongeallokeerde voorraad of 'n tekort aan roumateriaal met genoegsame kwaliteit of hoeveelheid om 'n bemarkingsbehoefte te bevredig. Verskaffers moet prioritiseer word in terme van strategiese belangrikheid en aankoop-besluitnemers moet kristalhelder dink oor watter strategie om te volg met elke kwaliteitssegment en verskaffer, sodat die regte hoeveelheid en volume teen die mees ekonomiese prys aangekoop word. Aankoopbesluitnemers moet die aankoop- en markomgewing evalueer vir geleenthede en bedreigings wat 'n invloed kan hê op hul vermoë om roumateriaal van hul verskaffingskorps aan te koop, en moet maatreëls in plek stel om beheer te neem oor die moontlike effek van daardie onsekerhede. Maatreëls sluit in die differensiasie tussen druifaankope en wynaankope om die voordele van elk maksimaal te benut. Aankoopsbeamptes moet 'n aksieplan vestig om die risiko van koste, beskikbaarheid en kwaliteit te beperk deur in verbintenisse te belê met lojale vertrouensverhoudings met vaardige verkaffers met kapasiteit. Die aankoopsfunksie moet op 'n professionele manier optree, om 'n beeld van pro-aktiewe aankope te bou en 'n fokus op lojale verskafferverhoudings te vestig.

Thesis (MBA)--Stellenbosch University, 2014. / Scenarios are a strategic tool that can stimulate strategic thinking, generate strategic foresight, provide a basis for testing existing strategies, explore and understand complexities of the future. In so doing they can aid decision making and contribute to preparation for the future. As such, this research paper used scenarios to explore a number of plausible futures for the South African Wine Industry in order to stimulate strategic thinking and conversations, pave the way for new ideas and approaches and encourage innovation. This can prepare both the industry and wine producers for possible challenges that they may face in the future. The scenario development process started with an extensive exploration of the existing industry, which included industry trends and patterns as well as factors within the external environment that influence the strategic landscape. Three key driving forces were identified in the external environment which could potentially have the largest impact on the future of the industry. These are impacts of climate change, local industry consolidation and buying power changes. Five scenarios for the South African Wine Industry were developed for the year 2025 based on these driving forces. These scenarios reflected these key driving forces under different circumstances, which provided different perspectives related to their impacts. The scenarios introduced alternative futures which range from one that envisages a consolidated local wine industry which focuses on the export market as a result of the opportunities presented by extreme weather events resulting from global climate change, to a scenario that is characterised by negligible changes in the structure of the local industry and where high buying power changes the industry dynamics and key success factors. A set of main findings relating to each scenario was formulated. These findings were examined in order to identify implications and make recommendations that could be useful to consider and aid strategy development for the industry, as well as for the benefit of individual wine producers. Key findings related to the impact of these key driving forces as well as the risks and potential opportunities that they could present for the industry under certain circumstances.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2009. / Saccharomyces cerevisiae has been used for millennia for the leavening of dough and in the production of alcoholic beverages such as beer and wine. More recently, it is being used as cell factories for the production of important pharmaceutical products. S. cerevisiae has also been extensively used as a model organism for studying many genetic and biochemical processes within the eukaryotic cell. Since the completion of a yeast genome sequence, many functional analysis projects have emerged with the aim of elucidating the functions of the unidentified genes revealed by the genome sequence. One of the most relevant approaches consisted in the construction of a collection of mutants deficient in all single genes, either in a haploid background for non-essential genes, or as heterozygous diploids for essential genes. This collection of strains can be subjected to phenotypic screens that might reveal the function of unknown genes or add to our understanding of already annotated genes. While this approach is promising, it also bears some limitations. For instance, many mutants have no overt phenotypes and some phenotypes do not obviously showcase the function of the encoded protein. In this study, S. cerevisiae strains with single deletions of genes involved in pyruvate metabolism were selected from the Euroscarf deletion library. Pyruvate is a central intermediate of glycolysis, and pyruvate metabolism largely defines the general distribution of carbon flux in the cell. These mutants were screened for modified fermentation kinetics or modified carbon flux under wine fermentative conditions, an environment that had not been previously used for the analysis of these mutants. A strain disrupted in the PDA1 gene, which encodes the E1α subunit of the pyruvate dehydrogenase showed a significant change in phenotype when grown in wine fermentative conditions. In particular, the mutant displayed a prolonged lag phase, but upon entering exponential growth, fermented significantly faster than the wild type strain and completed alcoholic fermentation in a shorter period of time. This phenotype could be of significant industrial interest. The mutant phenotype was further investigated through disruption of the gene in the same as well as in different genetic backgrounds, and through complementation of the PDA1 deletion with a plasmid-born wild type copy. The data show that the PDA1 gene disruption is not solely responsible for the observed phenotypes under wine fermentative conditions. We therefore propose that secondary mutations have contributed to the mutant phenotype. This study shows that phenotypes attributed to a specific gene in mutants of the Euroscarf library should always be confirmed before performing consequent experiments and drawing significant conclusions.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2006. / The quality of wine is influenced by numerous factors of which the grapes, winemaking techniques and effective quality control are to name a few. The use of new techniques should be cost effective and always have a positive influence on the wine quality. The addition of commercial tannins to wine is a fairly new technique and the effects of these additions at the concentrations prescribed have not been investigated in detail. The commercial tannins can be added to wine for different reasons, which may include: stabilisation of colour, increasing the aging potential, to modify aromas, promote precipitation of proteins, limit the effect of laccase activity, substrate for micro-oxygenation, to act as a redox buffer and structural and mouth feel modification. The reason for the addition determines the type of commercial tannin that is used, the timing of the addition and the dosage used.

Thesis (MScAgric) -- Stellenbosch University, 2005. / ENGLISH ABSTRACT: Winemakers or producers are under constant pressure to reduce the operational costs for the production of wine. The reason for this being threefold: Firstly, the number of cellars and estates locally, and internationally, has grown immensely. Thus, the competition on both the national and international front has put producers under pressure to reduce their production cost in order to survive the explosion of brand possibilities on the consumer's horizons. Secondly, the exchange rate has been one of the most unpredictable variables which highlight the importance of scenario planning and sufficient financial planning in order to overcome significant exchange rate fluctuations which may cause financial strain for the business. Thirdly, the benefits of using expensive oak barrels for the maturation of premium quality wines are undisputable. These benefits include the clarification and decarbonation of wines, decrease in the astringency of tannins ("softening of tannins"), the evolution of colour, providing complementary oak aromas which increase the complexity and finesse of these wines and stabilising the colloid structure of the maturing wine. The greatest disadvantages remain nevertheless that it is a costly and labour intensive operation. Oak is an essential part of the flavour profile of many premium quality wines, and there is still a growing market demand for these wines. The use of oak barrels for the maturation of premium red wines, incorporates a specific flavour dimension to the wine (and adding value), has been the traditional way of storing wines. Well known cellars and Estates all over the world have build remarkable profiles and identities for their brands. To alter any principles regarding the use of oak will alter the style of the wines and will beyond any doubt influence their brand image negatively. Chapter 1 gives an introduction and the main aims of the study. The phenolic composition of grapes and oak are a complex mixture of different molecules which are discussed in Chapter 2. These include those responsible for the colour (anthocyanins), taste (mainly the tannins) and aroma of the wine. The composition of the oak barrel can be influenced by its origin, seasoning of the oak, toasting of the staves, age of the barrel etc. These factors all affect the chemical composition of the oak (lactones, volatile phenols, carbohydrate volatiles, hydrolysable tannins etc.) and ultimately, the wine. The chemical reactions taking place in wine during ageing are also complex, which makes maturation and research of wine in oak a complex business. The challenge, thus, developed to sustain the flavour profiles (oak attributes) and to reduce the operational costs, without influencing the identity or profile of the brand negatively. The use of oak derived products like chips, dust, blocks, staves, balls and even extracts was proposed, although it is considered by-products of the cooperage profession. Some of the major disadvantages of the use of oak derived products still remain the limited control over the production process. This may lead to inconsistency in the quality of these products. Nevertheless, the use of oak derived products and the availability of these products have grown significantly and with it a need for research on this field. Chapter 3 address the results obtained from the maturation of Pinotage, which is uniquely South African, and Shiraz wines, in different oak type barrels (French vs. American vs. Russian), as well as treatments with various oak derived products, and the influence of these oak products on the evolution of colour, phenolic development and quality of the wines during ageing. The results obtained in this project correlated with findings in the literature. The colour density, percentage of red pigment colour and S02 resistant pigments increased, especially in the first three to six months during ageing in barrels as a result of ellagic tannin extraction from the barrels and polymerisation reactions, but decreased later as maturation progresses as a result of precipitation. In some cases the use of oak increased the colour density significantly with almost 40%. The colour density, total red pigment colour and total phenolic composition decreased during bottle maturation as a result of polymerisation. No significant colour differences between the barrel types could, however, be detected. The use of oak derived products showed the same tendencies for all colour dimensions, although no significant differences could be detected between the treatments. The most significant difference was that new oak barrels contributed more to the development of colour compared to the oak treatments. The Gelatine index gives an indication of the degree of polymerisation of tannins; higher values will indicate tannins which are highly reactive and will cause an astringent mouth feel. The values should decrease as maturation progresses and tannins polymerise. Little differences between barrel types (French vs. American vs. Russian) were found in the one Shiraz, but in the two Pintage wines the index was the lowest in the wines matured in French oak after 36 months bottle ageing. Sensorial tests indicated little quality differences after 36 months between the different oak types The American oak barrels had, in general, a more "oaky bouquet", even after 36 months in the bottle. Pinotage matured with different alternative oak products showed that chips added to barrels tended to give a higher oak aroma, with a lower fruit compared to the other treatments. The same wine matured in new barrels, as expected, also had a very high oak aroma compared to the same wine matured in older barrels. This led to a higher fruit perception in the latter wines. Lees contact is a practice more commonly used in the production of white wines, but may be a dangerous practice in the production of red wines. Chapter 4 reports on the effect of lees contact during ageing of red wine on the micro flora and colour after 12 month maturation. No significant differences in microbial analysis were detected during of barrel maturation between the wines matured in the lees and the filtered wines for acetic acid, yeast and lactic acid bacteria. The initial pH differences during cold maceration and fermentation, however, did influence these numbers, with higher numbers being observed at higher pH values. However, colour differences could be detected. The concentration of yellow brown pigments (measured at 420 nm) was lower in the lees matured wines than in the filtered· wines which underwent malolactic fermentation in the barrel. Other colour differences that could be detected were higher colour density and total red pigment colour in wines as a result of longer skin contact (due to slower alcoholic fermentation rate). Thus, manipulation of the skins during alcoholic fermentation, the use of barrels and/or oak derived products in various stages of vinification and maturation of wines and additional practices as maturation on lees may be thus be used to set a certain style of wine which meet a specific market demand, trend or style. Chapter 5 summarises the results obtained and future research to be done on wood and wine. This study, however, clearly showed that the origin and oak type does not influence the colour as much as the aroma and taste of red wine under South African conditions. / AFRIKAANSE OPSOMMING; Wynmakers of produsente word onder gedurige druk geplaas om die produksiekoste van wyn te verlaag. Die redes hiervoor is drieledig: Eerstens het die getal kelders en landgoedere op nasionale en internasionale vlak geweldig toegeneem. Dus, die kompetisie op beide nasionale en internasionale gebied plaas produsente onder druk om die produksie koste van die wyn te verminder om sodoende finansieel die ontploffing van nuwe moontlike wyne op die horison van die verbruiker te oorleef. Tweedens, die wisselkoers was altyd een van die meer onvoorspelbare veranderlikes wat die belangrikheid van scenario-beplanning en weldeurdagte finansiele beplanning beklemtoon om sodoende groat veranderinge in die wisselkoers, wat moontlike finansiele druk in die besigheid mag veroorsaak, te oorkom. Derdens, een van die grootste uitgawes in die produksie proses van is die verouderingskomponent van kwaliteitswyn. Die voordele van die gebruik van eikehout vate in die verouderingsproses van rooiwyne is welbekend. Hierdie voordele sluit in die suiwering van die wyn in terme van soliede partikels , dekarbonisering (C02-ontgasting}, afname in die vrank smaak ("sagtheid van die tanniene), die ontwikkeling van die kleur van die wyn, toevoeging van komplementere hout boeketstowwe wat bydrae tot die kompleksiteit van die wyn, asook die stabilisering van die kollo"idale struktuur van die wyn. Die grootste nadeel bly, nieteenstaande, die geweldige koste verbonde aan vate, asook die hantering en onderhoud daarvan. Eike hout verwante boeketstowwe is 'n onmisbare komponent van die aroma profiel van baie kwaliteitswyne. Daar is 'n groeiende mark vir hierdie tipe wyne. Die gebruik van eikehout vate vir die veroudering van kwaliteitswyne, behalwe die bydrae van belangrike geurstowwe (een waarde), was nog altyd 'n tradisionele stap in die proses. Beroemde kelders reg oor die wereld het uitmuntende mark identiteite vir hulle self geskep, asook 'n "spesifieke identiteit" vir hulle wyn. Om enige beginsels aangaande die gebruik van eikehout te verander, sal sander twyfel die wynstyl verander en moontlik 'n negatiewe effek op die kelder se identiteit he. Hoofstuk 1 gee 'n inleiding en die hoof doelstellings van die studie. Die fenoliese samestelling van druiwe en eikehout bestaan uit 'n komplekse mengsel van verskillende molekules wat in Hoofstuk 2 beskryf word. Hierdie sluit in daardie verantwoordelik vir die kleur (antosianiene), die smaak (hoofsaaklik tanniene) en die aroma van die wyn. Die samestelling van die eikevat kan beinvloed deur die oorsprong, veroudering van die hout, roostering, ouderdom van die vat ens. Hierdie faktore beinvloed almal die samestelling van die houtvat (laktone, vlugtige fenole, hidroliseerbare tanniene ens.) en uiteindelik, die wyn. Die chemiese reaksies wat plaasvind tydens die veroudering van wyn is ook kompleks, wat die veroudering en navorsing van wyn in vate 'n komplekse proses kan maak. Die uitdaging, dus, het ontstaan om die organoleptiese profiel van die wyn (eikehout boeketstowwe) te behou en terselftertyd die produksiekoste van die wyn te verlaag. Die gebruik van eikehout verwante produkte soos skaafsels, blokkies, stawe en balke en selfs eikehout ekstrakte is aanbeveel, alhoewel dit gesien word as afvalprodukte van die kuiperye Een van die grootste nadele van eikehout alternatiewe produkte is egter die beperkte kwaliteitskontrole oor die produksieproses. Dit mag lei tot wisselvalligheid in die kwaliteit van hierdie produkte. Nieteenstaande het die gebruik van eike houtverwante produkte en die beskikbaarheid van hierdie produkte geweldig toegeneem en tesame daarmee die behoefte aan navorsing hieroor. Hoofstuk 3 bespreek resultate van die gebruik van verskillende eikehout tipe vate (Frans vs Russies vs Amerikaans), asook die gebruik van eikehout verwante produkte, op die kleur ontwikkeling, fenoliese samestelling en kwaliteit van Pinotage (eie aan Suid-Afrika) en Shiraz wyne gedurende vat en bottel veroudering. Die ontwikkeling van kleur het verskeie unieke dimensies en resultate wat verkry is in hierdie projek stem ooreen met literatuur. Die kleurdigtheid, persentasie rooi pigment en 802 weerstandbiedende pigmente het toegeneem met veroudering in houtvate (veral in die eerste drie tot ses maande) as gevolg van ellagitanniene wat geekstraeer word en gepolimerisasie, maar het later gedurende veroudering afgeneem as gevolg van presipitasie reaksies. In sekere gevalle het die kontak met hout die kleurdigtheid met tot 40% vermeerder. Die kleurdighteid, totale rooi pigmente en totale fenole het tydens bottelverouding afgeneem a.g.v. polimerisasie. Geen merkwaardige verskille kon egter tussen die verskillende vattipes gevind word nie. Verskille tussen die houtverwante produkte was ook klein en het diesefde tendense getoon as die vate. Nuwe vate se impak op die kleurprofiel en ontwikkeling van verouderde rooiwyne was egter meer beduidenswaardig as die gebruik van gebruikte vate en behandelings met eikehout verwante produkte. Die gelatien indeks verwys na die toestand van polimerisasie van tanniene. Hoer waardes kan verwag word in jong wyne en dui op hoogs reaktiewe tanniene. Die waarde sal afneem soos tanniene polimere vorm met veroudering en sal dus 'n veel minder vrank mondgevoel tot gevolg he. Klein verskille tussen die vat tipes (Frans vs Amerikaans vs Russies) is opgemerk in die een Shiraz, maar in die twee Pinotage wyne was die indeks die laagste in die wyne verouder in Franse eikehout na 36 maande se bottelveroudering. Sensoriese toetse het aangedui dat daar klein verskille gevind is tussen die verskillende eiketipes. Die wyn verouder in Amerikaanse eik het, in die algemeen, 'n sterker eikehoutkarakter gehad na 36 maande bottelveroudering. Wyn verouder met verskillende alternatiewe houtprodukte het aangetoon dat eikehouskaafels in vate 'n sterker eikehoutkarakter aan die wyn gegee het met 'n laer vrugtige aroma in vergelyking met die ander behandelings. Dieselfde wyn verouder in nuwe vate het oak, soos verwag, 'n sterk hout boeket gehad in vergelyking met die verouder in ouer vate. Dit het dan oak gelei dat laasgenoemde wyne 'n sterker vrug aroma gehad het. Veroudering van wit wyne op moer is 'n algemene praktyk, alhoewel dit minder toegepas word op rooiwyne as gevolg van verwante gevare. Hoofstuk 4 bespreek die effek van moerkontak op die mikrobiese en kleursamestelling van rooiwyn tydens 12 maande se houtveroudering. Geen noemenswaardige verskille is egter verkry tussen die wyne verouder op die moer en die filtreerde wyne vir asynsuur-, melksuurbateriee en gisgetalle nie. Aanvanklike pH verskille tydens koue masserasie en alkoholiese fermentasie het egter hierdie getalle beinvloed, met hoer ·getalle verkry in die hoer pH wyn. Die wyne wat appelmelksuurgisting in die vate ondergaan het en verouder is op die moer het egter 'n laer konsentrasie geelbruin pigmente (gemeet by 420 nm) as die gefiltreerde wyne. Ander kleurverskille sluit in hoer kleurdigtheid en totale rooi pigmente as gevolg van langer dopkontak (stadiger alkoholiese fermentasie). Manipulering van die doppe voor en tydens alkoholiese gisting, die gebruik van eikehoutvate of eikehoutverwante produkte, of kombinasies daarvan tydens verskillende produksie fases en ander praktyke soos moer kontak, kan dus gebruik word am 'n sekere styl wyn op markversoek daar te stel. Hoofstuk 5 som die resultate op, asook toekomstige navorsingsmoontlikhede wat op die gebied van hout en wyn gedoen kan word. Hierdie studie het egter duidelik aangedui dat die eikehout oorsprong en tipe die kleur nie so baie beinvloed soos die aroma en smaak van die wyn onder Suid-Afrikaanse kondisies nie.