Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The importance of indigenous fruit wines is not well researched and documented. There is a need to develop and exploit these valuable food resources through improved production practices, storage, preservation and utilization technologies. The maruia fruit is beneficial in many ways, it can be used for making juice, jam, beer or can be eaten as a whole fruit. The highly nutritive nature of the fruit, its distinctive tropical flavor, its wild occurrence and demand by the local and international communities for the by-products of the fruit necessitated efforts to optimize the technological processes for the production of the possible by-products. This study focuses on the fermentation technology of the maruia fruit. The effect of enzymes prior to the fermentation process and post-fermentation was evaluated. For pre-fermentation processes we focused on the ability of commercial enzymes to increase juice yield, improve the clarification and filterability. For pre- and post-fermentation applications, aroma release was considered. The results indicated a significant increase in the yield depending on the enzyme used. An increase of at least 2% was recorded and a maximum of 12% yield increase was observed. The enzymes also had a phenomenal effect on the release of bound monoterpenes and hence enhancing the flavor of the juice. The panel of judges confirmed the results from the gas chromatography analyses by noting an increase in flavor intensity in the enzyme treated juice. The possibility of selecting a yeast strain that performs best during the fermentation of maruia pulp was also looked at. This study aimed at selecting a strain that produces wine and distillate with the typical maruia flavor complex. We showed the effect of the different yeast strains, in the wines and distillates, on the principal volatile compounds. We then correlated the performance of the different strains as perceived by the panel to the various volatile compounds. The effect of fermentation temperature on the performance of the different yeast strains was also considered. Fermenting the maruia pulp at different temperatures resulted in the production of wines and distillates with different volatile profiles for the different yeast strains. The wines and distillates fermented at a low temperature of 15°C were preferred to the wines and distillates fermented at 30°C. However, not all strains performed well at 15°C, strains like NT116 performed better at 30°C. The different commercial strains produced wines and distillates with significantly different flavor profiles. These differences in the flavor profiles were reflected in the sensory evaluation where, depending on the interaction of the volatile compounds some wines and distillates were preferred to others. The effect of the different commercial enzymes and yeast strains should thereof be further evaluated and optimized on a larger scale. This would greatly help prevent variation in quality of the fermented by-products of the maruia fruit. / AFRIKAANSE OPSOMMING: Die belang van inheemse vrugtewyne is nie goed nagevors en gedokumenteer nie. Daar is 'n behoefte om hierdie waardevolle voedselbronne te ontwikkel en te benut, deur verbeterde produksiepraktyke, storing, preservering en benuttingstegnologieë. Die maroelavrug is veelsydig op baie wyses, deurdat dit gebruik word vir die maak van sap, konfyt, bier, of as heel vrug geëet kan word. Die vrug is hoog in voedingswaarde, het In kenmerkende tropiese geur, kom wild voor, en is in aanvraag by plaaslike en internasionale gemeenskappe vir die by-produkte van die vrug. Dit maak dit essensieel om die tegnologiese prosesse vir die produksie van hierdie moontlike by-produkte te optimiseer. Hierdie studie fokus op die fermentasie-tegnologie van die maroelavrug. Die effek van ensieme voor en na die fermentasie-proses is geëvalueer. Vir prosesse wat voor fermentasie plaasvind, het ons gefokus op die vermoë van kommersiële ensieme om sapopbrengs te verhoog, asook om verheldering en filtrering te verbeter. Vir beide voor- en na-fermentasie toepassings is die vrystelling van aroma gemonitor. Die resultate dui op 'n betekenisvolle verhoging in die sapopbrengs, afhangende van die ensiem wat gebruik is. 'n Verhoging van ten minste 2% is opgeteken, en 'n maksimum van 12% opbrengsverhoging is waargeneem. Die ensieme het ook 'n geweldige effek op die vrystelling van gebonde monoterpene gehad, en dus die verhoging in die geur van die sap. Die proepaneel het die resultate bevestig van die gaschromatografie-analises, deur 'n verhoging in die geurintensiteit in die ensiembehandelde sap te bemerk. Daar is ook gekyk na die moontlikheid om 'n gisras te selekteer wat die beste presteer tydens die fermentasie van maroela-pulp. Hierdie studie het die doelstelling gehad om In gisras te selekteer wat wyn en distillaat produseer met In tipiese maroelageurkompleks. Ons het die effek van verskillende gisrasse aangedui in die wyne en distillate, op grond van van vlugtige komponente. Ons het dan die prestasie van die verskillende rasse, soos waargeneem deur die paneel, gekorrelleer met die verskeie vlugtige komponente. Die effek van fermentasie-temperatuur op die werkverrigting van die verskillende gisrasse is ook in ag geneem. Fermentasie van die maroela-pulp by verskillende temperature het gelei tot die produksie van wyne en distillate met verskillende vlugtige profiele vir die verskillende gisrasse. Die wyne en distillate wat by In laer temperatuur van 15°C gefermenteer is, is verkies bo die wyne en distillate wat by 30°C gefermenteer is. Alle rasse het egter nie baie goed presteer by 15°C nie, soos byvoorbeeld NT116 wat beter presteer het by 30°C. Die verskillende kommersiële rasse het wyne en distillate geproduseer met betekenisvol verskillende geurprofiele. Hierdie verskille in geurprofiele is gereflekteer in die sensoriese evaluering waar, afhangende van die interaksie van die vlugtige komponente, sommige wyne en distillate bo ander verkies is. Die effek van die verskillende kommersiële ensieme en gisrasse moet verkieslik verder op groter skaal geëvalueer en geoptimiseer word. Dit sal veral help om variasie in kwaliteit van die gefermenteerde by-produkte van die maroelavrug te voorkom.

Thesis (MSc)--Stellenbosch University, 1990. / ENGLISH ABSTRACT: To remain competitive in the market place, the South African wine industry will have to direct well-planned yeast strain-development programmes. However, the winemaker can only benefit from the extensive biochemical and molecular information of the yeast cell and the impressive arsenal of genetic techniques available, if the wine industry defines its requirements in genetic terms. The successful application of these genetic and recombinant deoxyribonucleic acid (DNA) techniques in breeding programmes depends on the availability of rapid and reliable techniques to differentiate between parental and hybrid strains. Ten strains of Saccharomyces cerevisiae used for commercial production of wine in South Africa, were characterised by electrophoretic banding patterns of total soluble cell proteins, DNA restriction fragments and chromosomal DNA. Variations in the protein and DNA profiles of strains N6, N21, N66, N76, N95 and N97 were apparent in the number, position and intensity of the bands. Strains N93 and N181 originated from the same culture and, as expected, displayed the same characteristic protein, DNA restriction fragment and chromosomal banding patterns. Similar protein and DNA profiles were also obtained for killer strain N96 and strain N91. Strain N91 is a derivative of strain N96, cured of the K2 killer character. Results obtained by electrophoretic fingerprinting and karyotyping corresponded well, indicating that these techniques are valuable in the identification and quality control of industrial wine yeasts. The value of electrophoretic fingerprinting and karyotyping was also demonstrated in a breeding programme. The aim of this breeding programme was to obtain hybrids that combine the desired oenological characteristics of strains N76 and N96, and of strains N96 and N181. The protein banding patterns of hybrids USM21, USM22 and USM23 were identical and contained a combination of prominent unique bands present in the profiles of parental strains, N76 and N96H (N96H is a haploid derived from N96). The DNA restriction fragment profiles of hybrids USM21, USM22 and USM23 contained slight variations, whereas their profiles were quite different from those of their parental strains, N76 and N96H. The contour clamped homogeneous electric field (CHEF) karyotypes of hybrids USM21, USM22 and USM23 were identical but differed from those of their parental strains, N76 and N96H. The protein profiles of hybrid USM30 and its parental strains, N96H and N181, were similar, whereas their DNA restriction fragment banding patterns and CHEF karyotypes showed discrete differences. In conclusion, protein and DNA fingerprinting techniques were found to be valuable in selecting four hybrid killer strains after mass spore-cell mating. These four killer hybrids contain desirable oenological properties long sought after by the South African wine industry. Fermentation trials and evaluation of these hybrids were conducted independently by the Deparment of Oenology, University of Stellenbosch and by Stellenbosch Farmers' Winery and they have now been released for commercial wine production. / AFRIKAANSE OPSOMMING: Om mededingend in die handel te bly, sal die Suid-Afrikaanse wynbedryf weloorwoe gisras-ontwikkelingsprogramme moet loads. Die wynmaker sal egter slegs voordeel kan trek uit die omvattende biochemiese en molekul...Lre inligting oor die gissel en die indrukwekkende arsenaal van genetiese tegnieke wat beskikbaar is, indien die wynbedryf sy vereistes in genetiese terme definieer. Die suksesvolle toepassing van hierdie genetiese en rekombinante deoksiribonuklei"ensuur (DNA) tegnieke in telingsprogramme sal afhang van die beskikbaarheid van vinnige en betroubare tegnieke om tussen ouerlike en hibried-rasse te onderskei. Tien rasse van Saccharomyces cerevisiae wat vir kommersiele wynproduksie in Suid-Afrika gebruik word, is met behulp van elektroforetiese bandpatrone van totale oplosbare selprotei"ene, DNA-restriksiefragmente en chromosomale DNA gekarakteriseer. Variasies in die protei"en- en DNA-profiele van rasse N6, N21, N66, N76, N95 en N97 het geblyk uit die aantal, posisie en intensiteit van die bande. Rasse N93 en N181 het uit dieselfde kultuur ontstaan en het, soos verwag, dieselfde karakteristieke protei"en-, DNA-restriksiefragmenten chromosomale bandpatrone getoon. Soortgelyke protei"en en DNA profiele is ook vir killerras N96 en ras N91 verkry. Ras N91 is 'n variant van ras N96 wat die K2 killerkenmerk verloor het. Resultate wat met behulp van elektroforetiese vingermerking en kariotipering verkry is, het goed ooreengestem en dui daarop dat hierdie tegnieke waardevol is vir die identifisering en beheer van industriele giste. Die waarde van elektroforetiese vingermerking en kariotipering in telingsprogramme is ook gedemonstreer. Die doel van hierdie telingsprogram was om hibriede te kry waarin die gewenste kenmerke van rasse N76 en N96, en van rasse N96 en N181, gekombineer is. Die protei"en-bandpatrone van hibriede USM21, USM22 en USM23 was identies en het 'n kombinasie van prominente unieke bande, teenwoordig in die profiele van hul ourlike rasse, N76 en N96H (N96H is 'n haploi"de afstammeling van N96), bevat. Die DNArestriksiefragment- profiele van hibriede USM21, USM22 en USM23 toon geringe onderlinge verskille, maar hul profiele het wesenlik van die van hul ouerlike rasse, N76 en N96H, verskil. Die kontoergeklampde-homogene-elektriese-veld (CHEF) elektroforetiese kariotipes van hibriede USM21, USM22 en USM23 was identies, maar het verskil van die van hul ouerlike rasse, N76 en N96H. Die protei"enprofiele van hibried USM30 en sy ouerlike rasse, N96H en N181, was soortgelyk, terwyl hul DNA-restriksiefragment-bandpatrone en CHEF-kariotipes diskrete verskille getoon het. Ten slotte is gevind dat prote'ien- en DNAvingermerkingstegnieke waardevol was in die seleksie van vier hibried-killerrasse na massa spoor-sel paring. Hierdie vier killerhibriede beskik oor gewenste wynkundige eienskappe waarna die Suid-Afrikaanse wynbedryf reeds lank soek. Fermentasie-proewe en evaluering is onafhanklik deur die Departement Wynkunde, Universitiet van Stellenbosch en deur Stellenbosch-Boerewynmakery gedoen en hulle is nou vir kommersiele wynproduksie vrygestel.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Key research areas in modern enology are related to the production of wine of consistent quality, as well as to the improvement of existing wine quality through the enhancement of the sensory properties of wine. The formation of glycerol during alcoholic fermentation is highly relevant to both these issues. Since the early years of the zo" century, glycerol has been positively associated with the quality of wine and it is thought to impart important mouth-feel sensations such as "viscosity", "smoothness" and "body". In general, it is considered that glycerol concentrations higher than those normally found in wine, can contribute towards the improvement of wine quality. It has also been suggested that increased concentrations of glycerol can enhance the aroma of wine. On the basis of these perceptions, several strategies have been developed to favour the production of glycerol during the fermentation process and over a period of years, a large volume of data has been collected that relates to various aspects regarding glycerol production during alcoholic fermentation. To date, however, several aspects regarding the relationship between glycerol and wine quality remain unclear. The reasons for this situation can mainly be ascribed to the lack of reliable analytical data to serve as a basis for investigating the relationship between glycerol and wine quality, as well as the preponderance of empirical and anecdotal evidence. Despite numerous opinions regarding optimal glycerol concentrations in wine, glycerol is indeed seldom assayed on a routine basis and targets with respect to specific wine grape cultivars and glycerol concentrations have largely remained unspecified. To date, very little information regarding glycerol concentrations in South African wines has been published. The analytical techniques that are most frequently used for the quantification of glycerol in grape juice, fermenting must and wine are not easily automated and this aspect placed severe limitations on the generation of large volumes of analytical data on glycerol concentrations in these matrices. This project was undertaken with the aim to holistically address some of the unresolved issues relating to the relationship between glycerol and wine quality. This also implied the development and optimisation of analytical techniques suitable for the rapid and accurate determination of glycerol in fermentation media, as well as in finished wine. In the first stage of this project a quantitative database was established that contained the analytical data on the glycerol concentrations of a statistically significant number of wines of adjudged quality, as well as additional information for each wine regarding the geographic origin, vintage, routine chemical analyses and the yeast strain(s) used for the production of the wine. The relevance of glycerol in wine for the modern South African winemaker was evaluated through the establishment of a quantitative database that contained the opinions of an expert panel of 15 South African winemakers, enologists and wine chemists on topics relating to glycerol in wine. In the second stage of the project the data captured in the databases were used to investigate aspects regarding the relationship between glycerol and wine quality. From the data captured in the qualitative database, it was clear that the topic regarding glycerol in wine was important to the South African winemakers and it was also evident that there was a need for the development and optimisation of methods suitable for the routine analysis of the glycerol concentrations in grape juice, fermenting must and wine. The opinions of the panel members also highlighted the issue that the mouth-feel property of wine was considered to be an area where the quality of some wines could be further improved. The quantitative database contained the information on the glycerol concentrations of 450 commercial South African table wines of adjudged quality. The premium cultivars Chardonnay, Chenin blanc, Sauvignon blanc, Cabernet Sauvignon, Merlot, Shiraz and Pinotage were used for the purpose of investigating the relationship between glycerol concentration and wine quality. The wines represented a wide variety of wine styles, including dry white, off-dry white, dry red and late harvest wines. The average glycerol concentration was significantly associated with the wine style. In white wines the average glycerol concentration was much lower than in the red wines (6.82 gIL versus 10.49 gIL, respectively). No significant relationship between the final glycerol concentration and the geographic origin, vintage and the yeast strain used for the fermentation was found. Wine quality could not be significantly associated with glycerol concentration in the red wines. In the white wines, the relationship between glycerol concentration and wine quality was significant, but due to the very small differences in the average glycerol concentrations of the wines of different quality ratings, the statistical significance is probably of little practical value. The effect of glycerol on the volatility of a selection of esters and higher alcohols was also investigated. Solid-phase microextraction, followed by gas chromatography, was used to analyse the composition of the headspace at equilibrium between the liquid phase and the gas phase of a model wine, and a dry white wine that contained a basal concentration of 5.4 gIL glycerol. Results showed that incremental increases in the glycerol concentrations over a range of 1 -10 gIL in the model wine and in a Chenin blanc wine, were not accompanied by a proportional increase or decrease in the abundance of the aroma components in the headspace. The volatile components tested were isoamyl acetate, ethyl butyrate, ethyl valerate, ethyl lactate, ethyl hexanoate, hexyl acetate, isoamyl alcohol and isobutanol. For all the volatile components tested, the difference between the headspace composition of samples containing the lowest glycerol concentration, and those containing the highest glycerol concentration, was not significant. However, sufficient experimental evidence was obtained to indicate that increasing glycerol concentrations had an effect on the volatility of aroma components, and that the effect is of a complex and non-linear nature. In the third phase of the work Fourier transform infrared spectroscopy (FT-IR) was used to establish and optimise methods for the accurate and rapid quantification of glycerol in wine. For this purpose calibrations were developed for the quantification of glycerol in dry wine and late harvest wines. The accuracy of prediction was evaluated by means of the standard error of prediction that was 0.38 gIL for the dry wines and 0.65 gIL for the sweet wines. Large variations are introduced in the FT-IR spectra of wine by factors such as process technology, cultivar and geographic origin, and this variation can have an effect on the accuracy of the analytical data generated when employing FT-IR spectroscopy. Using glycerol prediction in wine as a model system, principal component analysis of the FT-IR spectra was done in order to establish quality control measures for the detection of poorly predicted, or outlier samples. A classification model, based on principal component analysis, was established that enabled the interpretation and classification of the outlier samples in the data set in 100% of the cases tested. This work forms the basis for expanding the quality control measures for the detection of wines of which the FT-IR spectra are highly unnatural, as well as for establishing quality control measures to ensure that accurate analytical data are generated when FT-IR is used. FT-IR spectroscopy was also used to develop a rapid screen for the evaluation of the fermentation profiles of wine yeasts. For this purpose, a selection of wine yeasts, which included commercial wine yeasts frequently used in winemaking in South Africa, as well as a selection of hybrid Saccharomyces cerevisiae yeasts, that were obtained through a selective breeding strategy aimed at increasing glycerol concentrations were used. Calibrations necessary for the accurate quantification of glycerol, volatile acidity, ethanol, reducing sugar and glucose, in Chenin blanc must and a synthetic must were developed and optimised. This work forms the basis upon which the scope of the analysis, both in terms of the number of components that can be measured, as well as the medium in which the yeasts are being evaluated, can be enlarged. This would be valuable for future applications in both the research as well as the industrial environment. The method that was developed serves to illustrate how this application can play a supportive role in yeast development programmes, through the speeding up of the initial stages of yeast strain evaluation. / AFRIKAANSE OPSOMMING: Navorsing in moderne wynkunde is sterk gefokus op die produksie van wyn waarvan die kwaliteit van In volhoubare goeie peil is, sowel as die verdere verbetering van bestaande wynkwaliteit, deur In verhoging van die sensoriese eienskappe van wyn. Die vorming van gliserol tydens alkoholiese fermentasie het betrekking op beide hierdie aspekte. In Opvatting wat wyd gehuldig word en wat reeds sedert die vroeë jare van die 20e eeu geld, impliseer dat gliserol In positiewe bydrae lewer tot wynkwaliteit. Oor die algemeen word dit beskou dat gliserolvlakke hoër as wat normaalweg in wyn aangetref word, kan bydra om die kwaliteit van die wyn nog verder te vehoog. Daar is ook spekulasie dat verhoogde gliserolvlakke in wyn die intensiteit van die aroma van wyn kan verhoog. Hierdie opvattings het tot gevolg gehad dat veskeie strategieë ontwikkel is om die gliserol vlakke wat tydens die fermentasieproses gevorm word, te verhoog. Baie min inligting oor die gliserolinhoud van Suid-Afrikaanse wyn is tot onlangs gepubliseer. Ten spyte van die opvattings oor gliserol en wynkwaliteit wat reeds oor In lang tydperk gehuldig word, bly sekere aspekte van die verwantskap tussen gliserol en wynkwaliteit nog steeds onduidelik. Redes vir hierdie situasie kan hoofsaaklik toegeskryf word aan die totale afwesigheid van betroubare en substansiële eksperimentele data wat as basis kan dien vir die evaluering van die algemene opvattings aangaande die verwantskap tussen gliserol en wynkwaliteit. Die inligting wat wel beskikbaar is, is verder ook oorwegend van In empiriese aard. Huidig word gliserol selde op In roetine basis in die analitiese laboratorium bepaal, hoofsaaklik omdat die bestaande metodes tydrowend is en nie maklik geoutomatiseer kan word nie. In hierdie studie is In kwantitatiewe databasis opgestel waarin die inligting ten opsigte van die gliserolvlakke van 450 kommersiële Suid-Afrikaanse tafelwyne waarvan die kwaliteit beoordeel is, vervat is. Die kultivars Chardonnay, Chenin blanc, Sauvignon blanc, Cabernet Sauvignon, Merlot, Shiraz en Pinotage is gebruik vir hierdie doel en die seleksie van wyne was verteenwoordigend van In wye verskeidenheid wynstyle, insluitende droë wit-, halfdroë wit-, droë rooi- en laatoeswyne. Die gemiddelde gliserolvlakke in die witwyne was heelwat laer as die gemidelde gliserolvlakke in die droë rooiwyne (6.82 gIL teenoor 10.49 gIL, onderskeidelik). Geen beduidende verwantskap kon aangetoon word tussen die gliserolkonsentrasie in die wyn en die geografiese oorsprong, oesjaar, en die gisras wat gebruik is in die produksie van die wyn nie. Die kwaliteit van rooiwyn kon nie beduidend met die gliserolkonsentrasie geassosieer word nie. In die geval van wit wyn was die verwantskap statisties beduidend, maar die verskille was klein en moontlik nie van veel praktiese waarde nie. Die aktualiteit van gliserol vir die moderne Suid-Afrikaanse wynmaker is geëvalueer op grond van die opinies van In paneel van 15 Suid-Afrikaanse kundiges, rakende aspekte wat verband hou met die algemene opvattings oor gliserol en wyn. Die paneel het bestaan uit wynmakers, wynkundiges en chemici. Die opinie van die panel is deur middel van "n vraelys bekom en is vervat in "n kwalitatiewe databasis. Die resultate van hierdie menigspeiling het getoon dat gliserol wel vir die Suid- Afrikaanse wynmakers belangrik is en dit het ook die behoefte uitgewys vir die ontwikkeling en optimisering van metodes wat geskik is vir die roetine analyses van gliserol in wyn. Die invloed van gliserol op die vlugtigheid van "n seleksie van hoëralkohole en esters is ondersoek in "n model wyn sowel as "n wit wyn, waarvan die basiese gliserolkonsentrasie 5.4 gIL was. Soliede-fase mikroekstraksie van die gasfase van wyn is opgevolg met "n gaschromatografiese analise. Resultate het getoon dat "n stapsgewyse toename in die gliserol konsentrasie, oor "n konsentrasie reeks van 0 - 10 gIL in die model wyn, en 0 - 15 gIL in die wit wyn, nie gepaard gegaan het met "n reglynige toename of afname in die konsentrasie van die aromakomponente nie. Vir al die komponente wat ondersoek is, was die samestelling van die gasfase in monsters wat die laagste gliserol konsentrasie gehad het, teenoor dié wat die hoogste gliserol konsentrasie gehad het, nie beduidend nie. Nietemin het die resultate getoon dat gliserol wel "n effek het op die vlugtigheid van die aroma komponente wat in hierdie ondersoek gebruik is, maar dat die aard van die effek kompleks en nie-liniê is. Fourier-transformasie-infrarooispektroskopie (FT-IR) is gebruik om die metodes vir die analise van gliserol in wyn sodanig te optimiser, dat vinnige en akkurate bepalings op "n roetine basis in wyn gedoen kan word. Kalibrasies is ontwikkel vir die kwantifisering van gliserol in droëwyn en laatoeswyn. Die standaard voorspellingsfout van die kalibrasies wat ontwikkel is, was 0.38 gIL in droëwyn en 0.65 gIL in die geval van laatoeswyn. Inherente variasie in die FT-IR-spektra word deur eksterne faktore soos die proses tegnologie wat gebruik is om die wyn te berei, die kultivar en geografiese oorsprong van die wyn veroorsaak en hierdie variasie kan "n effek hê op die voorspelingsakkuraatheid van FT-IR spektroskopie. Om die effek van hierdie variasie op die akkuraarheid van die analitiese data te evalueer, is die voorspelling van gliserol as modelsisteem gebruik. Hoofkomponentanalise van die FT-IR spektra is gedoen om dié wyne met onnatuurlike FT-IR-spektra te identifiseer, ten einde beheer oor die akkuraatheid van die analitiese data uit te oefen. "n Verdere model wat ook gebaseer is op hoofkomponentanalise van die FT-IR-wynspektra is ontwikkel vir die interpretasie en klassifikasie van wynmonsters met onnatuurlike FT-IRspektra. Met die model wat ontwikkel is kon onnatuurlike wynmonsters met "n akkuraatheid van 100% gëidentifiseer word. Hierdie werk vorm die basis waarop kwaliteitsbeheer verder uitgebrei kan word sodat wyne met onnatuurlike spektra gëidentifiseer kan word, sowel as om te verseker dat akkurate data gegenereer word as FT-IR as analitiese metode gebruik word vir die kwantifisering van gliserol in wyn. FT-IR spektroskopie is ook gebruik om "n vinnige skandeerproses te ontwikkel waarmee die fermentasieprofiele van wyngiste geëvalueer kan word. Die seleksie giste wat vir hierdie doel gebruik is, sluit kommersiële Suid-Afrikaanse wyngiste in, sowel as hibriede Saccharomyces cerevisia-giste wat normaalweg hoër vlakke van gliserol tydens die fermentasieproses produseer. Kalibrasies is ontwikkel vir die akkurate kwantifisering van gliserol, vlugtige suur, alkohol, reduserende suiker en glukose, in Chenin blanc-mos sowel as in 'n sintetiese medium. Hierdie werk vorm die basis waarop verdere uitbreidings gedoen kan word, sodat meer metaboliete gemeet kan word en 'n groter verskeidenheid van fermentasiemedia gebruik kan word. Hierdie ontwikkeling is waardevol vir toekomstige toepassings in die navorsings- sowel as die industriële omgewing. Die metode wat ontwikkel is illustreer ook hoe hierdie toepassing 'n ondersteunende rol kan speel in wyngisontwikkelingsprogramme deur die aanvanklike evalueringsproses van die giste te versnel.

Thesis(DScAgric.)--Stellenbosch University, 1932. / No Abstract Available

Thesis (PhD(Agric))--Stellenbosch University, 1970. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The terms business model and business model innovation have only gained prominence over the past two decades, whilst little of the research has been applied in a South African context. The main objective of this thesis was to ascertain the reasons for success of a local business through the research and application of the themes of business models, business model innovation and blue ocean strategy to a local organisation. The subject matter of the thesis was Van Loveren Family Wine Cellar, a family-owned South African wine farm that has seen significant success over the past 15 years in a highly competitive and fragmented local market. To complete this process, it was also necessary to gain an understanding of both the global and local wine industries, and how South Africa has grown within this environment. The format of the thesis is a case study, selected because of its relevance to gaining a rich understanding of the context of the research and the processes enacted, thereby facilitating the main objectives. The case study approach also provides a tool to aid in the education of business strategy students, allowing the principles to be applied to new scenarios. The findings of the study include that there has been a shift in both consumption and production of wine from the traditional Old World to the innovative New World. This shift is being driven by new consumers of wine who are less concerned with the mystique and legacy of Old World wine, instead demanding wines that fit their lifestyles through easy drinking taste profiles with an ease of selection. This phenomenon is present in South Africa, where growth in the market is seen at lower price points. New consumers who are selecting wines that compete with existing alcohol alternatives as gateway products are driving this demand. Van Loveren launched their Four Cousins Rosé in 2000, with exponential growth experienced between 2004 and 2008, driving the product to be one of South Africa’s best-selling brands. The findings of the study were that the Van Loveren Family Cellar had positioned itself, through business model innovation, to capture the growth in new wine drinkers. Van Loveren had built a business model that provided a framework within which strategy can take on competitors. Core to their success were the long-term relationships with key buyers and the collaborative partnerships that allowed Van Loveren to utilise external capabilities as part of their own business. The success was also based on the leap of faith to enter the market in a sweeter taste profile, through the development of a brand that resonated with consumers, and in packaging that provided an attractive price point. The combination of these decisions allowed Van Loveren to capture uncontested market and grow exponentially.

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

Thesis (MA) -- Stellenbosch University, 1932. / VOORWOORD: Die doel van hierdie verhandleing is in die eerste plek om daarop te wys dat in Suid-Afrika meer wyn geproduseer word as wat tans van die hand gesit kan word teen 'n prys wat die produsente genoegsaam sal vergoed. Uit die oorproduksie en die heersende lae pryse volg dit dat die posiesie van die wynboere erg kritiek en haglik is. Die industrie gaan nou juis weer deur diepe waters en iets moet gedoen word om die bedryf van ondergang te red en vir die toekoms op 'n vaste basis te plaas.

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

Thesis MSc(Agric)--Stellenbosch University, 1979. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming