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.

Thesis (MSc)--Stellenbosch University, 2002. / Full text to be digitised and attached to bibliographic record. / ENGLISH ABSTRACT: The winemaking process constitutes a unique ecological niche that involves the interaction of yeasts, lactic acid bacteria and acetic acid bacteria. Saccharomyces cerevisiae has established its importance as a wine yeast and also proven itself as a reliable starter culture organism. Its primary role is to convert the grape sugar into alcohol and, secondly, its metabolic activities result in the production of higher alcohols, fatty acids and esters, which are important flavour and aroma compounds that are essential for consistent and predictable wine quality. There is a growing consumer demand for wine containing lower levels of alcohol and chemical preservatives. Glucose oxidase (GOX) has received considerable research interest regarding its potential application in the wine industry to reduce alcohol levels and as a biocontrol agent. Several physical processes are used for the removal or reduction of alcohol in wine and some of them are sometimes used in combination. These processes tend to involve expensive equipment and can be intensive from a processing point of view. An alternative approach was introduced with the concept of treating grape must with GOX to reduce the glucose content of the must, and therefore produce a wine with a reduced alcohol content after fermentation. Due to the demanding nature of modern winemaking practices and sophisticated wine markets, there is an ever-growing quest for specialised wine yeast strains possessing a wide range of optimised, improved or novel oenological properties. The first and main objective of this study was to genetically engineer wine yeasts to produce wine with a reduced alcohol content. In order to do this, the structural glucose oxidase (gox) gene of Aspergillus niger was cloned into an integration vector (Ylp5) containing the yeast mating pheromone a-factor secretion signal (MFa1 s) and the phosphoglycerate kinase 1 gene promoter and terminator (PGK1PT). This PGK1p-MFa1sgox- PGKh gene cassette (designated GOX1) was introduced into a laboratory strain of S. cerevisiae (~1278). Results obtained indicated the production of biologically active glucose oxidase and showed that it is secreted into the culture medium. This would mean that the enzyme will convert the glucose to gluconic acid in the medium before the yeast cells are able to metabolise the glucose to ethanol. Microvinifications performed with Chardonnay grapes showed that the laboratory yeast starter cultures transformed with GOX1 were indeed able to reduce the total amount of alcohol in the finished product. The second objective of this study involved the potential application of GOX as a biocontrol agent. Screening was performed for wine spoilage microorganisms, such as acetic acid bacteria and lactic acid bacteria, using plate assays. The wine spoilage microorganisms tested formed different sized inhibition zones, indicating varying degrees of inhibition. The inhibition of some of the wine spoilage microorganisms was confirmed under a scanning electron microscope. The total collapse of the bacterial cell wáll could be seen and might be explained by the fact that a final product of the GOX enzymatic reaction is hydrogen peroxide (H202). The produced H202 leads to hyperbaric oxygen toxicity, a result of the peroxidation of the membrane lipid, and a strong oxidising effect on the bacterial cell, which is the cause of the destruction of basic molecular structures, such as nucleic acids and cell proteins. In this exciting age of molecular yeast genetics and modern biotechnology, this study could pave the way for the development of wine yeast starter culture strains for the production of wine with a lower alcohol content and reduced levels of chemical preservatives, such as sulphur dioxide. The use of genetically modified organisms (GMOs) within the wine industry is a limiting factor at present and credible means must be found to effectively address the concerns of traditionalists within the wine industry and the negative overreaction by some consumer groups. There is a vast potential benefit to the wine consumer and industry alike and the first recombinant wine products therefore should unmistakably demonstrate safe products free of potentially harmful compounds, and have organoleptic, hygienic and economic advantages for both the wine producer and consumer. / AFRIKAANSE OPSOMMING: Die wynmaakproses behels 'n ekologiese interaksie tussen gis, asynsuurbakterieë en melksuurbakterieë. Saccharomyces cerevisiae het homself alreeds bewys as 'n belangrike en betroubare inisiëringsgis in wyn. Die hoofdoel van die gis is om druifsuikers na etanol om te skakel. Tweedens lei die gis se metaboliese aktiwiteite tot die produksie van hoër alkohole, vetsure en esters, wat tot die konsekwente voorspelbare smaak en aromaverbindings in herhaalbare kwaliteit wyn bydra. Daar is 'n toenemende aanvraag na wyne met 'n laer alkoholinhoud en minder preserveermiddels. Glukoseoksidase (GOX) het heelwat navorsing in die wynindustrie uitgelok omdat dit gebruik kan word om die alkoholinhoud in wyn te verlaag, asook as 'n biologiese beheermiddel kan funksioneer. Daar is reeds sekere fisiese prosesse wat gebruik kan word om die alkohol in wyn te verwyder of te verminder. Sommige van hierdie prosesse word soms in kombinasie gebruik. Die nadeel is egter dat hierdie prosesse baie duur en intensief is, veral ten opsigte van prosessering. 'n Alternatief om die alkoholinhoud van wyn te verlaag, het egter na vore gekom toe daar voorgestel is om die mos met GOX te behandel. As gevolg van die veeleisende aard van moderne wynmaakpraktyke en gesofistikeerde wynmarkte, is daar 'n nimmereindigende soektog na meer gespesialiseerde wyngisrasse wat 'n wye reeks van geoptimiseerde en verbeterde, en selfs unieke, wynkundige einskappe bevat. Die hoofdoelwit van hierdie navorsingsprojek behels die genetiese manipulasie van 'n gisras sodat dit in staat is om wyn met 'n laer alkoholinhoud te produseer. Om hierdie doel te verwesentlik, is die strukturele glukoseoksidasegeen (gox) van Aspergillus niger in 'n integreringsvektor gekloneer. Transkripsie-inisiëring en -terminering is deur fosfogliseraatkinase-1-promotor en -termineerder (PGK1PT) bewerkstellig. Die a-spesifieke gisferomoon-a-faktor (MFa1 s) is gebruik om die uitskeiding van GOX uit die gis te bewerkstellig. Saam vorm bogenoemde die PGK1p-MFals-gox-PGKh-geenkasset, wat as GOX1 bekend is. GOX1 is na 'n labaratoriumras van S. cerevisiae (:E1278) getransformeer. Resultate dui aan dat biologies aktiewe GOX geproduseer en uitgeskei word. Dit beteken dat van die glukose in die medium reeds na glukoonsuur omgesit sal word voordat die gis dit kan begin benut en alkohol produseer. Kleinskaalse wynmaakprosesse wat met Chardonnay-druiwe en GOX-produserende labaratoriumgis uitgevoer is, het inderdaad tot laer alkoholpersentasies gelei. Die tweede doelwit van die navorsingsprojek was om te bepaal of GOX die potensiaal as biologiese beheermiddel het. Daar is ondersoek ingestel na sekere wynbederfsorganismes soos asynsuur- en melksuurbakterieë en die inhibisie van die organismes is op agarplate gemonitor. Verskillende grade van inhibisie, soos die grootte van die inhibisiesone, was sigbaar vir die verskillende wynbederfsorganismes wat getoets is. Die inhibiese van sekere wynbederfsorganismes is ook met behulp van 'n skandeerelektronmikroskoop bevestig. Die totale ineenstorting van die bakteriële selwand was sigbaar en kan verklaar word deur die teenwoordigheid van waterstofperoksied (H202). Laasgenoemde is 'n byproduk van die laaste metaboliese reaksie en staan as 'n antimikrobiese middel bekend. Die byproduk (H202) gee aanleiding tot hiperbariese suurstoftoksisiteit, 'n gevolg van die peroksidasie van membraanlipiede en 'n sterk oksiderende effek t.o.v. die bakteriële selwand. Dit lei tot die vernietiging van die basiese molekulêre strukture, soos die nukleïensure en selproteïene. Tydens hierdie opwindende era van molekulêre gisgenetika en biotegnologie kan hierdie navorsing die fondament lê vir die ontwikkeling van 'n wyngiskultuur wat in staat is om wyn met 'n laer alkoholinhoud te produseer. Die gebruik van geneties gemanupileerde organismes (GMO's) in die wynbedryf is egter nog 'n beperkende faktor. 'n Geloofwaardige manier moet dus gevind word om die bekommernisse van tradisionaliste, asook die negatiewe oorreaksies van sommige verbruikers, aan te spreek en hok te slaan. Daar is groot potensiaal en voordele vir beide die verbruiker en industrie. Dit is dus belangrik dat die eerste rekombinante wynprodukte wat die mark betree, veilig en vry van potensieel skadelike verbindings is, asook organoleptiese, higiëniese en ekonomiese voordele toon te opsigte van beide die wynprodusent en gebruiker.

Thesis (MSc)--Stellenbosch University, 2003. / Full text to be digitised and attached to bibliographic record. / ENGLISH ABSTRACT: Winemaking is an age-old tradition that dates back to as early as 6000 BC. In our modern era there are several insects and microorganisms that pose a threat to the grapevine, the environment and the final wine product. Farmers and winemakers are becoming aware of the threat and the fight against disease, spoilage and/or pathogenic microorganisms is on the rise. Currently, the natural environment is being altered through rural developments, pollution and disaster, which in turn is responsible for altering the natural micro flora. The result is a harsh battle between man and microorganism. The weapon used often against microorganisms is chemical preservatives, such as sulphur dioxide. These chemical preservatives change the nutritional value, quality and wholesomeness of the wine. Chemical preservatives suppress the quality of the wine with a reduction in wine consumption by the consumers. Until the 18th century, wine was regarded as a safe drink and prescribed by doctors. In the zo" century alcohol consumption became the focus point of some health campaigners. Medical science restored the good name of wine in the 1990s when it came to light that moderate red wine consumption may aid in preventing heart disease and assist in stress management. The only drawback that lowers consumption levels is the use of chemical preservatives. It is of utmost importance to place the focus on health issues and the development of natural preservation methods that are environmentally friendly and contributes to the overall wholesomeness of the wine. Due to these demands, the scientific community placed the focus of research projects on the development and enhancement of biopreservation methods, in order to minimise chemical preservation use. One of the most promising biocontrol agents is bacteriocins. These proteinaceous molecules produced by various lactic acid bacteria exert antimicrobial activity towards closely related organism. Research has shown that bacteriocins may aid in the prevention of wine-spoilage and enhance natural preservation techniques. Most of the research on biopreservation in food and beverages has been performed on the bacteriocins of LAB. No evidence could be found that indicated bacteriocin production by wine isolated LAB in South Africa. This study is therefore, of utmost importance and is considered to be novel pioneering work for the South African wine industry. The main objective of this study was to screen wine isolated LAB for the production of antimicrobial and/or antifungal compounds. This was followed by the isolation and characterisation of the produced bacteriocins. This study forms part of a greater project that focuses on wine preservation, under the auspices of the Institute for Wine Biotechnology.The research results in this study indicated the production of bacteriocins by wine isolated LAB of South African origin. It was found that numerous isolates exerted antimicrobial activity towards other wine associated LAB. The most predominant species that gave the highest activity was Lactobacillus brevis and Lactobacillus paracasei. Experimental results indicated that the bacteriocins produced by these two species were thermo-stable and active over a wide pH range, including the temperatures and pH values that reign in the South African wine environment. The antimicrobial activity was lost after treatment with proteolytic enzymes, such as proteinase K and lysozyme. The size, production and growth kinetic curves of the bacteriocins under investigation showed similar results that are comparable to other findings in the literature. Antifungal activity was detected against Botryfis cinerea that indicated limited inhibitory activity towards spore germination, but had no effect on hyphal growth. This study provides novel information regarding bacteriocin production by LAB isolated from the South African wine industry. The results indicate the suitability of these bacteriocins as possible biopreservatives in the wine environment. The proposed results obtained in this study will aid in the development of bacteriocinproducing, tailored made wine yeast or LAB that may in future, play vital roles in the winemaking process. / AFRIKAANSE OPSOMMING: Wynmaak is 'n eeu oue tradisie wat terugdateer tot so vroeg soos 6000 jaar v.C. In ons moderne eeu is daar verskeie insekte en mikro-organismes wat In bedreiging vir die wingerdstok, asook die omgewing en die finale wynproduk inhou. Boere en wynmakers word al hoe meer bewus van hierdie bedreiging, terwyl die stryd teen siektes, bederf en/of patogene mikro-organismes ook aan die toeneem is. Tans word die natuurlike omgewing deur landelike ontwikkeling, besoedeling en natuurlike rampe verander, wat op sy beurt weer verantwoordelik is vir die verandering van mikroflora. Die gevolg is 'n harde stryd tussen die mens en mikro-organismes. Die wapen wat gereeld ingespan word in die stryd teen mikro-organismes, is chemiese preserveermiddels, soos swaweidioksied. Hierdie chemiese preserveermiddels verander die voedingswaarde, kwaliteit en die voedsaamheid van die wyn. Dit onderdruk ook die gehalte van wyn, wat meebring dat minder wyn deur die verbruiker gedrink word. Tot en met die agtiende eeu is wyn deur dokters as 'n veilige drankie voorgeskryf. In die twintigste eeu het alkoholverbruik die fokuspunt van gesondheidskamvegters geword. In die 1990's het die mediese wetenskap wyn se goeie naam in ere herstel toe dit aan die lig gekom het dat In matige verbruik van rooiwyn moontlik hartsiektes kan voorkom en help om stres te beheer. Die enigste nadelige faktor wat verbruikersvlakke verlaag, is die gebruik van chemiese preserveermiddels. Dit is uiters noodsaaklik om die fokus op gesondheidskwessies te plaas en die ontwikkeling van natuurlike preserveermetodes wat omgewingsvriendelik is en tot die algehele voedsaamheid van wyn bydra. As gevolg van hierdie eise het wetenskaplikes die fokus geplaas op navorsingsprojekte vir die ontwikkeling en verbetering van biopreserveringsmetodes met die doelom die gebruik van chemiese preserveermiddels te verminder. Een van die belowendste biokontrolemiddels is bakteriosiene. Hierdie proteïenagtige molekule word deur verskeie melksuurbakterieë vervaardig en oefen anti-mikrobiese aktiwiteit teenoor nabyverwante organismes uit. Navorsing het getoon dat bakteriosiene moontlik kan help in die voorkoming van wynbederf en natuurlike preserveertegnieke kan verbeter. Die meeste van die navorsing op biopreservering in voedsel en drank is op die bakteriosiene van melksuurbakterieë uitgevoer. Geen bewys kon gevind word in Suid Afrika wat bakteriosienproduksie deur wyn-geïsoleerde melksuurbakterieë aangedui het nie. Hierdie studie is daarom baie belangrik en word as baanbreker werk vir die Suid Afrikaanse wynbedryf beskou. Die hoofdoel van hierdie studie was om wyn-geïsoleerde melksuurbakterieë vir die produksie van anti-mikrobiese en/of anti-fungiese substanse te toets. Dit is gevolg deur die isolasie en karakterisering van die geproduseerde bakteriosiene. Hierdie studie maak deel uit van 'n groter projek wat fokus op wynpreservering en wat onder leiding van die Instituut van Wynbiotegnologie uitgevoer word. Navorsingsresultate van hierdie studie dui op die produksie van bakteriosiene deur wyn-geïsoleerde melksuurbakterieë van Suid Afrikaanse oorsrong. Daar is gevind dat verskeie isolate anti-mikrobiese aktiwiteit teenoor ander wynverwante malksuurbakterieë uitgeoefen het. Die oorheersende spesie wat die hoogste aktiwiteit getoon het, was Lactobacillus brevis en Lactobacillus paracasei. Eksperimentele uitslae dui daarop dat die bakteriosiene wat deur hierdie twee spesies geproduseer word, termostabiel en aktief is oor 'n wye pH reeks, insluitende die temperature en pH-waardes wat in die Suid Afrikaanse wynomgewing voorkom. Die anti-mikrobiese aktiwiteit het verlore gegaan na behandeling met proteolitiese ensieme soos proteïnase K. Die groote, produksie en groeikinetika kurwes van die bakteriosiene wat ondersoek is, toon vergelykbare resultate met ander bevindings in die literatuur. Anti-fungiese aktiwiteit is opgemerk teen Botrytis cinerea, wat beperkte inhiberende aktiwiteit ten opsigte van spoorontkieming aangedui het, maar geen effek op hifegroei gehad nie. Hierdie studie verskaf nuwe inligting aangaande bakteriosienproduksie deur melksuurbakterieë wat van die Suid Afrikaanse wynomgewing geïsoleer is. Die resultate dui op die geskiktheid van hierdie bakteriosiene as moontlike biopreserveermiddels in die wynbedryf. Die voorgestelde resultate deur hierdie studie verkry sal help in die ontwikkeling van bakteriosien produserende, spesifiek vervaardigse wyngis of melksuurbakterieë, wat in die toekoms 'n baie belangrike rol in die wynmaakproses sal speel.

Thesis (MScAgric)--Stellenbosch University, 1954. / No Abstract Available

Thesis (MScAgric)--Stellenbosch University, 1955. / No Abstract Available

Thesis (MSc)--Stellenbosch University, 1958. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming